pvc grounding

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  #1  
Old 07-17-02, 04:31 PM
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pvc grounding

I am looking for a way to ground 40 year old 2 wire bx in a plastic box. Can I use a metal clamp around the cable and ground to outlet or should I use GFI??
 
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  #2  
Old 07-17-02, 05:00 PM
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Bx in a plastic box

Will there be only one cable or more than one? The NEC requires you to connect the cable jackets together. You can use half inch grounding bushings or wedges that you can buy at an electrical supply house. You connect the grounding terminal of the device to the grounding bushing or wedge that is connected to the cable's connector.
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  #3  
Old 07-17-02, 09:29 PM
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hornetd, would you provide the NEC article number that allows the metal flex of a two wire BX cable as an equipment grounding conductor for me?

Curious

Wg
 
  #4  
Old 07-17-02, 10:16 PM
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40 year old cable / my bad.

If you are trying to point out that I may have missed the age of the cable while focussing on the need to bond the cable connectors to each other and to the Grounding terminal of the device you are correct.

The test that was developed by the then National Board of Fire Underwriters to validate the grounding path in these older cable installations is beyond the scope of a DIY forum as it requires the skilled use of high quality metering equipment that can be calibrated for accuracy. That test should only be performed by an experienced journeyman or master electrician who has been certified in the necessary electrical testing techniques.
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  #5  
Old 07-18-02, 08:00 AM
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The corrogated armor of BX may not be used as an equipment grounding conductor. Even newer BX carries the silver wire that some like to call the ground and it is not! It is merely a bond from one end to the other of the BX.

I don't see how you would be able to ground this device since there is no grounding means present.

If you have the ability to rerun the cable then you could use an armored cable that carries an equipment grounding conductor, that's the only way I see to do it.

PS. Even if you test the cable and it shows a continuous path, it's still against code to use the corregation as a grounding means.
 
  #6  
Old 07-18-02, 09:23 AM
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Given that BX is the trade name for AC (Armored Cable). You will go to Art. 250.118 Types of Equipment Grounding Conductors
Go down to section (9)

Art 250.118(9) Armor of Type AC cable as provided in 320.108

Art 320.108 Equipment Grounding
Type AC cable shall provide an adequate path for equipment grounding as required by 250.4(A)(5) or 250.4(B)(4)

Art 250.4(A)(5)
This is the article about providing a low impedance path..etc... The earth shall not be used as the sole equipment grounding conductor.

250.4(B)(4)
Same thing as above, but for ungrounded systems.

The way I see it by 250.118(9) the armor is suitable for providing an equipment ground.
 
  #7  
Old 07-18-02, 10:35 AM
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Hey Dave, let's stop and think about this a minute. You are correct that the armor can be used as an ECG provided that the cable has that little wire that runs from one end to the other and is terminated properly at the ends. However, what is that wire attached to? The question said it terminated in a plastic box, which you can't ground and further it's in a house that is 40 years old. You would have to be sure that the A/C cable does in fact tie to a GROUNDED source in order to use the armor as an ECG, otherwise you are fooling yourself.
 
  #8  
Old 07-18-02, 11:15 AM
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DaveB.inVa
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Originally posted by Sparksone42
The corrogated armor of BX may not be used as an equipment grounding conductor

PS. Even if you test the cable and it shows a continuous path, it's still against code to use the corregation as a grounding means.
Im not trying to fool myself or anyone at all, are you?

You stated that it was against code to use the armor as a grounding means. I merely stated that it was and provided code references to prove so.

If the armor was in fact grounded to the service then I would have no problem using it for a code compliant equipment ground using the methods that hornetd described earlier.
 

Last edited by DaveB.inVa; 07-18-02 at 12:01 PM.
  #9  
Old 07-18-02, 04:09 PM
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Jasontv8 is talking about a 40 year old cable. If you look at the history of UL listed AC cable it is not that old. The Original older style two wire BX cable was installed that many years ago and is neither listed nor labled as metal clad cable, or type A/C cable nor flexible metallic conduit.

The old BX cable that Jasontv8 is talking about does not meet the construction requirements of Type AC cable.

See the following construction specs showing support of what sparksone42 is claiming. The metal flex of the old BX cable is not approved listed nor labled as an equipment grounding path.

AC cable requires a grounding conductor or metal strip to augment the flexible protection of type AC cable to be used as AC cable or as equipment grounding conductor.

COPIED SECTION OF;

NEC 2002
320.100 Construction.
Type AC cable shall have an armor of flexible metal tape and shall have an internal bonding strip of copper or aluminum in intimate contact with the armor for its entire length.

COPIED SECTION OF NEC HANDBOOK 2002 COMMENTARY;

The armor of Type AC cable is recognized as an equipment grounding conductor by 250.118. The required internal bonding strip can be simply cut off at the termination of the armored cable, or it can be bent back on the armor. It is not necessary to connect it to an equipment grounding terminal. It reduces the inductive reactance of the spiral armor and increases the armor's effectiveness as an equipment ground. Many installers use this strip to help prevent the insulating bushing required by 320.40 (the “red head”) from falling out during rough wiring.

OPINION;
Sparksone42, I believe that if you read the installation requirements of AC cable you must use listed connectors approved for use with AC cable. I didn't look it up but as far as I remember AC cable could only be connected to a steel box to make a recognized grounding path. Plastic box would leave you no normal method of connecting the armor to the device grouding connection. This would be something that should be considered.

I am still curious if there is an article that approves the older BX cable's armor to be used as an equipment grounding conductor but can find no statement allowing this to be done.

Curious

Wg
 
  #10  
Old 07-18-02, 08:44 PM
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Here would be a good time to have an older code book, which I dont have. An instructor of mine has a 47 NEC so maybe I could get him to take a look.

Ill admit I dont know what kind of grounding means horntd is referring to, but if theyre listed for use in a plastic box and if the older BX is listed I would be feel fine using it as an EGC and would accept it as a code compliant installation.
 
  #11  
Old 07-19-02, 05:50 AM
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DaveB, in 1950 era there was no equipment grounding conductor even in the thought of the electrical field as far as I know.

My question is why is everyone so set on using a flex cable that even in the flexible metal conduit rules states that 3/8" size can not be used for equipment grounding? The MC cable is required to have an equipment grounding conductor not using the metal flex as an approved grounding path. The AC cable does use the metal flex as an equipment grounding path but only if augmented by the metal strip required to run the entire length of the cable. The flexible metal conduit is limited to 6' lengths and only 1/2" if used as a grouding path. Flexible metal tubing

(8) Flexible metallic tubing where the tubing is terminated in fittings listed for grounding and meeting the following conditions:
a. The circuit conductors contained in the tubing are protected by overcurrent devices rated at 20 amperes or less.
b. The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible metal conduit in the same ground return path does not exceed 1.8 m (6 ft).

As far as I know there is no flexible metal conduit that is sized 3/8" that allows it to be used as a grounding path in lengths longer than 6'.

I am confused where anyone can justify using a 50 year old 3/8" flexible metal jacket as a grouding path when todays flexible metal jacket is limited to 6' lengths at best if used as an equipment grounding path.

Would someone explain why the strong feelings in wanting to use this old product in a manner it was then nor ever intended even if manufactured today? This strong push to accept the old BX cable jacket as a grouding path is not just present in this post but I have seen the argument Nationwide. Why to make a job easier? Why hasn't the NEC had a Code change request allowing this BX cable jacket to be used as a grouding path that has passed the Code committees in all these years?

If research was done on testing of this product it should be found that when a fault current occurs a 3/8" metal jacket emits sparks the full length of the metal jacket into the combustable materials in the areas where this 3/8" metal jacket is running.

The NEC clearly states that if you want to use an equipment grounding conductor for an existing two wire circuit that you can install a single insulated grounding conductor. There are at least two other methods of doing this two prong receptacle bit but yet there is a strong push to accept something that is clearly not allowed in the NEC.

Confused

Wg
 
  #12  
Old 07-19-02, 11:41 AM
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Bravo WG Well Said!! One thing I think we all missed is that it looks like he wants to ground the pvc. Can't be done!!

I even had an inspector ask me one time where my ground was for a pvc nipple in between a service disconnect and a transfer switch. At the time I was a second year apprentice, I turned to him and asked him if he was on the third rock from the sun. He looked at me strange and asked what I meant and I told him I would gladly ground that pvc if he could show me in the NEC how to do it. Needless to say he signed the permit and left without another word.
 
  #13  
Old 07-20-02, 04:21 PM
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Originally posted by Wgoodrich
DaveB, in 1950 era there was no equipment grounding conductor even in the thought of the electrical field as far as I know.

My question is why is everyone so set on using a flex cable that even in the flexible metal conduit rules states that 3/8" size can not be used for equipment grounding? The MC cable is required to have an equipment grounding conductor not using the metal flex as an approved grounding path. The AC cable does use the metal flex as an equipment grounding path but only if augmented by the metal strip required to run the entire length of the cable. The flexible metal conduit is limited to 6' lengths and only 1/2" if used as a grouding path. Flexible metal tubing

(8) Flexible metallic tubing where the tubing is terminated in fittings listed for grounding and meeting the following conditions:
a. The circuit conductors contained in the tubing are protected by overcurrent devices rated at 20 amperes or less.
b. The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible metal conduit in the same ground return path does not exceed 1.8 m (6 ft).

As far as I know there is no flexible metal conduit that is sized 3/8" that allows it to be used as a grounding path in lengths longer than 6'.

I am confused where anyone can justify using a 50 year old 3/8" flexible metal jacket as a grouding path when todays flexible metal jacket is limited to 6' lengths at best if used as an equipment grounding path.

Would someone explain why the strong feelings in wanting to use this old product in a manner it was then nor ever intended even if manufactured today? This strong push to accept the old BX cable jacket as a grouding path is not just present in this post but I have seen the argument Nationwide. Why to make a job easier? Why hasn't the NEC had a Code change request allowing this BX cable jacket to be used as a grouding path that has passed the Code committees in all these years?

If research was done on testing of this product it should be found that when a fault current occurs a 3/8" metal jacket emits sparks the full length of the metal jacket into the combustable materials in the areas where this 3/8" metal jacket is running.

The NEC clearly states that if you want to use an equipment grounding conductor for an existing two wire circuit that you can install a single insulated grounding conductor. There are at least two other methods of doing this two prong receptacle bit but yet there is a strong push to accept something that is clearly not allowed in the NEC.

Confused

Wg
Let me say first that it was never my attention to step forward as a champion of so called "field expedient" grounding methods. I am opposed to the use of the armor of of older BX cable as an Equipment Grounding Conductor unless the approval of the Authority Having Jurisdiction (AHJ) is obtained. Most AHJs will not even consider this or any other method that does not have the blessing of a nationally recognized electrical testing laboratory.
I only referred to the NBFU test to head off the inevitable suggestion that some field expedient test be applied. The NEC permits the AHJ to approve installations based on examination. Although there is a fine print note that suggests that listing and labeling can be used as a basis for determining suitability the article goes on to provide a long list of factors the AHJ should consider in examining installations. The absence of listing or labeling certainly puts the burden on the installer to demonstrate that the installation is safe for it's intended use. The NBFU ground pathway impedance test is one way to demonstrate to an AHJ that the new installation of a three wire grounding receptacle is suitable for the intended use. It is then up to the AHJ to accept or reject the method or material as installed.

An example of another installation that an AHJ might encounter might be helpful. The grounding electrode conductor (GEC) of a two hundred ampere service is run in the water line trench from the building served by the service to be inspected. The trench is four feet deep. The water line is non metallic. The trench is 200 feet long. The existing metal well casing will serve as a grounding electrode. The GEC consist of bare number two copper conductor. The AHJ could take two approaches to this installation. Since the number two copper wire is not in fact "encircling the building or structure," even though it is "in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG." He could turn it down and require the installation of two ground rods. The installing electrician than produces a ground impedance meter and a certificate of calibration to National Institute of Standards and Technology referenced level. He disconnects the number two copper from the metal well casing and test its ground impedance in the inspectors presence and demonstrates that the impedance of the installed number two copper conductor is four ohms. The existing ground rods for the service that is being replaced were driven at a 45 degree angle to cope with the shale laden soil. If you require the installation of ground rods they will be laid in the trench with the newly installed number two copper GEC. The acorn clamps for the ground rods will be placed around the #2 AWG GEC. Would you as the inspector require the installation of the two eight foot ground rods?

Apples and oranges you say. That is true but either fruit will prevent scurvy. If I run a number twelve or fourteen THHN wire green in color through the bored holes used to run the original BX for one run of cable to connect the grounding terminal of a new three wire grounding receptacle to the grounded buss bar of the service, as the code permits me to do, and I then demonstrate that the impedance of the grounding means specifically permitted by the code is greater than the existing cable armor would you still insist on the separate conductor methodology?
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110.3 Examination, Identification, Installation, and Use of Equipment.
(A) Examination. In judging equipment, considerations such as the following shall be evaluated:
(1) Suitability for installation and use in conformity with the provisions of this Code
 
  #14  
Old 07-21-02, 02:15 PM
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Hornetd, I am glad you are not a proponent of using a 3/8" metal jacket as a grounding path, in my opinion you are making a good judgement.

I am severely disappointed when I hear of electricians or AHJs that approve or use products or wiring methods that are not listed and labled or approved by documented testing methods whether by a testing labratory or by testing performed by that AHJ.

I am severly disappointed hearing of non tested products or wiring methods being installed by using the authority of an AHJ's ruling that has not researched the product's limits using accepted testing methods or approved testing labratories.

The risk involved in allowing products that have not been proven in the conditions they are being used is a very risky business. When we do this with electricity it is even more risky.

If an AHJ approves the use of a 3/8 flexible metal jacket for use as a grounding path it would be an obvious example that exactly what is mentioned above has happened.

Ironically I had to investigate and inspect a dwelling today that had a fire to have damaged their home. Upon seeing the cause of the fire I asked for and received from the owners permision to take pictures and use these pictures wherever it can be of help, as a learning tool for anyone who is not aware of the charicteristics of a faulted current while using the 3/8" metal jacket in excess of 6' long as a grounding path. Maybe some will understand the hazards involved in using this smaller metal jacket as a grounding path, and refrain from doing so.

I see no reason that an AHJ would approve that which the NEC refuses to approve for use as a grounding path.

Check out the following pictures taken today on the fire scene, may be of some help in making a decision concerning the 3/8" metal jacket being used as a grouding path. Take notice of the welding puddles of molten metal where the current tried to take the short cut across the wraps due to the resistance involved in the long metal tape, if the current instead was traveling around in circles the full length of that metal tape making up the 3/8" flex metal jacket. Notice the blow outs where the tape disintergrated to nothing. Try to consider that a conductor that is approximately 100" long would need a metal strip making up that 3/8" metal jacket as long as 1000 feet long or so making up all those wraps.

Notice the fire damage most likely caused by the hot metal and sparking emitted by the 3/8" metal jacket igniting the nearby wood most likely by the molten metal dripping onto the wood.

All this damage was done to that 3/8" metal jacket before a 20 amp breaker performed its interupting rating action. The 20 amp breaker did trip out but not until after the wood was ignited by the melt down of that 3/8" metal jacket.

http://www.homewiringandmore.com/sto...eldedshort.jpg

Hope this helps, just my opinion though,

Wg
 
  #15  
Old 07-21-02, 10:30 PM
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What about the questions I asked.

Is there any chance you will answer the questions I posed?

Great pictures. It would appear the local fire departement made a good stop.
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  #16  
Old 07-22-02, 12:00 PM
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Honetd, didn't know you had a question in the reply you issued. I saw what you said was a statement instead of a question. If you were intending that I issue my opinion as to whether I would accept those alternative wiring methods then I will try to issue what I believe and think of each scenerio you stated. Hope this helps.

YOu only printed part of rule 110.3 the remaining part left out I provided below;

Copied section of NEC 2002
NEC Rule;
110.3 Examination, Identification, Installation, and Use of Equipment.
(A) Examination. In judging equipment, considerations such as the following shall be evaluated:
(1) Suitability for installation and use in conformity with the provisions of this Code
FPN:Suitability of equipment use may be identified by a description marked on or provided with a product to identify the suitability of the product for a specific purpose, environment, or application. Suitability of equipment may be evidenced by listing or labeling.
(2) Mechanical strength and durability, including, for parts designed to enclose and protect other equipment, the adequacy of the protection thus provided
(3) Wire-bending and connection space
(4) Electrical insulation
(5) Heating effects under normal conditions of use and also under abnormal conditions likely to arise in service
(6) Arcing effects
(7) Classification by type, size, voltage, current capacity, and specific use
(8) Other factors that contribute to the practical safeguarding of persons using or likely to come in contact with the equipment

NEC HANDBOOK COMMENTARY;
For wire-bending and connection space in cabinets and cutout boxes, see 312.6, Table 312.6(A) and Table 312.6(B), and 312.7, 312.9, and 312.11. For wire-bending and connection space in other equipment, see the appropriate NEC article and section. For example, see 314.16 and 314.28 for outlet, device, pull, and junction boxes, as well as conduit bodies; 404.3 and 404.18 for switches; 408.3(F) for switchboards and panelboards; and 430.10 for motors and motor controllers.

NEC RULE;
(B) Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

NEC HANDBOOK COMMENTARY;
Manufacturers usually supply installation instructions with equipment for use by general contractors, erectors, electrical contractors, electrical inspectors, and others concerned with an installation. It is important to follow the listing or labeling installation instructions. For example, 210.52, second paragraph, permits permanently installed electric baseboard heaters to be equipped with receptacle outlets that meet the requirements for the wall space utilized by such heaters. The installation instructions for such permanent baseboard heaters indicate that these heaters should not be mounted beneath a receptacle. In dwelling units, it is common to use low-density heating units that measure in excess of 12 ft in length. Therefore, to meet the provisions of 210.52(A) and also the installation instructions, a receptacle must either be part of the heating unit or be installed in the floor close to the wall but not above the heating unit. (See 210.52, FPN, and Exhibit 210.23 for more specific details.)
In itself, 110.3 does not require listing or labeling of equipment. It does, however, require considerable evaluation of equipment. Section 110.2 requires that equipment be acceptable only if approved. The term approved is defined in Article 100 as acceptable to the authority having jurisdiction. Before issuing approval, the authority having jurisdiction (also defined in Article 100) may require evidence of compliance with 110.3(A). The most common form of this evidence considered acceptable by authorities having jurisdiction is a listing or labeling by a third party.
Some sections in the Code require listed or labeled equipment, such as 250.8, which includes the phrase “listed pressure connectors, listed clamps, or other listed means.”

OPINION;
The subject in this post is using the 3/8" metal jacket of older style BX cable as a grounding path. If we refer to 250.118.5 this metal jacket would have to be listed and labeled for use as an equipment grounding conductor. There is no listing and labeling of the older BX cable to be used as an equipment grounding conductor therefor it must not be used.

250.118 Types of Equipment Grounding Conductors.
The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:
(5) Flexible metal conduit where both the conduit and fittings are listed for grounding.


If you will read 250.118.B and 110.3.B It calls for listing a labeling in both rules, therefor the AHJ would be inviolation by approving that which is required to be listed for use as a grounding conductor.

If the AHJ did rule this 3/8" metal jacket to be approved and used as a grounding path then that AHJ did not follow the list of 1 through 8 which is also part of the rule when using 110.3.A and required to be followed in his or her evaluation of this product for approval.

It is rather obvious that the metal tape of a 3/8" flexible metal jacket is inadequate to be used as a grounding conductor by seeing the overall intent in the NEC wherever 3/8" metal flexible jacket is mentioned that it is not approved as a grounding path.


YOU SAID;
The grounding electrode conductor (GEC) of a two hundred ampere service is run in the water line trench from the building served by the service to be inspected. The trench is four feet deep. The water line is non metallic. The trench is 200 feet long. The existing metal well casing will serve as a grounding electrode. The GEC consist of bare number two copper conductor. The AHJ could take two approaches to this installation. Since the number two copper wire is not in fact "encircling the building or structure," even though it is "in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG." He could turn it down and require the installation of two ground rods.

OPINION;
There is a marked difference of a GEC [grounding electrode conductor] connecting to a metal well casing and a GE [grounding electrode] From what you discribe the 20' in direct contact with the earth of this grounding electrode conductor would have nothing to do with the AHJ's ruling. This grounding electrode is connected at both ends being the metal well casing and the main service rated panel or another NEC approved grounding electrode listed in Article 250.50 and 250.62 nor is it a violation of 250.64 in its installation method. What you have discribed is not a GROUNDING RING but only a grounding electrode conductor.

If this #2 copper 20' long is not connected at one end and its intent is to be used as a grounding electrode being a grounding ring it would be a violation because it does not meet the requirments making up a grounding ring. Neither could it be considered as a plate electrode also listed in 250.50 or 250.52.4 through 7 where none listed in 250.50 exists. The NEC leaves no room for any grounding electrode other than those listed and approved by the NEC.

In my opinion 110.3.A should be strictly adhered to using the listed 1 through 8 criteria to approve an alternative product and only when it is not possible to use what is listed and approved by the NEC.

If you want to create an experimental method of wiring then produce the records and testing available to have it approved by the NEC and qualified testing labratories to be used as an approved product not a short cut circumventing the NEC.

110.3.A should be used reluctantly with a major effort of following the methods of testing listed in 110.3.A. 1 through 8 to approve that alternative method of grounding. Was an engineer involved in this alternative method or was it a couple of electricians that didn't want to use a ground rod and wanted to take a short cut instead?

In my opinion alternative wiring methods not existing in the NEC should not be rebuked and stopped before use, but those alternative wiring methods should have documented testing and proving records available and filed by that AHJ before he or she approves that alternative product. Just standing over a trench looking at a product and saying looks good to me is not the intent of 110.3 in any manner.


YOU SAID;
The installing electrician than produces a ground impedance meter and a certificate of calibration to National Institute of Standards and Technology referenced level. He disconnects the number two copper from the metal well casing and test its ground impedance in the inspectors presence and demonstrates that the impedance of the installed number two copper conductor is four ohms.

Opinion
Was an engineer involved in these tests? Was the National Institue of Technology involved, did the NIT provide a record of electrosis reaction to this alternative wiring method. What other Institutes that are recognized in testing these alternative methods were involved in this alternative wiring method. What verifications and records has the AHJ kept and recorded to substantiate his or her ruling to approve this alternative wiring method?

YOU SAID;
The existing ground rods for the service that is being replaced were driven at a 45 degree angle to cope with the shale laden soil. If you require the installation of ground rods they will be laid in the trench with the newly installed number two copper GEC. The acorn clamps for the ground rods will be placed around the #2 AWG GEC. Would you as the inspector require the installation of the two eight foot ground rods?

REPLY;

If any of those listed grounding electrodes found in 250.50 are not available and if you are connecting that 2 awg copper grounding electrode conductor to that metal well casing then a supplemental grounding electrode must be installed. This supplemental grounding elctrode may be a ground rod buried a minimum of 30" deep and connected to that grounding electrode conductor at any convenient point. The 25 ohms to ground requirement for grounding electrodes does not apply to supplemental grounding electrodes.

No I would not require two ground rods in the condition that you discribe. YOu already meet the minimum safety standards as you discribed you installation.


YOU SAID;
Apples and oranges you say. That is true but either fruit will prevent scurvy. If I run a number twelve or fourteen THHN wire green in color through the bored holes used to run the original BX for one run of cable to connect the grounding terminal of a new three wire grounding receptacle to the grounded buss bar of the service, as the code permits me to do, and I then demonstrate that the impedance of the grounding means specifically permitted by the code is greater than the existing cable armor would you still insist on the separate conductor methodology?


REPLY;
When you install the green insulated THHN from that receptacle changed from a two prong receptacle to a three prong receptacle to the grounding terminal in the panel then you are no longer trying to use that 3/8" metal jacket that is not an approved grounding conductor. Therefor you have met the requirments of 250.130.

Just my opinion

Wg
 
  #17  
Old 07-24-02, 11:23 AM
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Let me see if I understand your answer on the installation of ground rods. You appear to be saying that the number two copper is a Grounding Electrode Conductor only and that it could never be considered an electrode.

OPINION;
There is a marked difference of a GEC [grounding electrode conductor] connecting to a metal well casing and a GE [grounding electrode] From what you describe the 20' in direct contact with the earth of this grounding electrode conductor would have nothing to do with the AHJ's ruling. This grounding electrode is connected at both ends being the metal well casing and the main service rated panel or another NEC approved grounding electrode listed in Article 250.50 and 250.62 nor is it a violation of 250.64 in its installation method. What you have described is not a GROUNDING RING but only a grounding electrode conductor.

If this #2 copper 20' long is not connected at one end and its intent is to be used as a grounding electrode being a grounding ring it would be a violation because it does not meet the requirements making up a grounding ring. Neither could it be considered as a plate electrode also listed in 250.50 or 250.52.4 through 7 where none listed in 250.50 exists. The NEC leaves no room for any grounding electrode other than those listed and approved by the NEC.

In my opinion 110.3.A should be strictly adhered to using the listed 1 through 8 criteria to approve an alternative product and only when it is not possible to use what is listed and approved by the NEC.

If you want to create an experimental method of wiring then produce the records and testing available to have it approved by the NEC and qualified testing laboratories to be used as an approved product not a short cut circumventing the NEC.

110.3.A should be used reluctantly with a major effort of following the methods of testing listed in 110.3.A. 1 through 8 to approve that alternative method of grounding. Was an engineer involved in this alternative method or was it a couple of electricians that didn't want to use a ground rod and wanted to take a short cut instead?

In my opinion alternative wiring methods not existing in the NEC should not be rebuked and stopped before use, but those alternative wiring methods should have documented testing and proving records available and filed by that AHJ before he or she approves that alternative product. Just standing over a trench looking at a product and saying looks good to me is not the intent of 110.3 in any manner.
No there wasn't a couple of electricians involved only one. As for that short cut I must have missed something because in my narrative I said that he has run over two hundred feet of grounding electrode conductor in order to make use of the well casing as a grounding electrode. I fail to see how a witnessed ground impedance test using a ground impedance meter calibrated to a NIST benchmark is "Just standing over a trench looking at a product and saying looks good to me." Leaving that aside you then go on to say;

"If any of those listed grounding electrodes found in 250.50 are not available and if you are connecting that 2 AWG copper grounding electrode conductor to that metal well casing then a supplemental grounding electrode must be installed. This supplemental grounding electrode may be a ground rod buried a minimum of 30" deep and connected to that grounding electrode conductor at any convenient point. The 25 ohms to ground requirement for grounding electrodes does not apply to supplemental grounding electrodes.

No I would not require two ground rods in the condition that you describe. YOu already meet the minimum safety standards as you described you installation."
The only electrode I have described in my example is the metal well casing. Perhaps my reference to the existing electrodes is what is causing the confusion. The existing electrodes are not a factor in the new service installation. The new service is not being installed in the same location as the old one. The old service equipment will be replaced with a lighting and appliance panel board. The building in which the old service is located will only have the existing ground rod as the grounding electrode system for that building. There is also a telephone company installed ground rod that could be bonded to the electrical service ground rod to create a grounding electrode system but as you know the NEC© would only require me to bond that rod to the electrical system grounding electrode with a number 6 AWG bonding conductor. The only connection between that ground rod and the service grounding electrode system will be the 100 ampere feeder's #8 CU equipment grounding conductor. Now mind you that feeders trench is fifty feet long and three feet deep but since you will not recognize any conductor laid in that trench as a grounding electrode I will not waste my customers money by up sizing the feeder's EGC to the size of a ground ring. In fact given your ruling that the #2 in the water line trench is only a grounding electrode conductor despite it's length, depth of bury, and demonstrably low impedance I might as well roll it up and save it for an installation were the inspector might appreciate the extraordinary effort I have gone to to provide a low impedance ground. For the job in your jurisdiction I would throw the required two ground rods in the bottom of the trench, connect them with the much less expensive twenty four feet of number six AWG Grounding Electrode Conductor and let it eat. At a distance of two hundred feet I cannot imagine that you could lawfully order the well casing used based on it being "available on the premises at each building or structure served."

I have wired buildings from central Africa to French Frigate Shoals and from southern Argentina to central Alaska. I can assure you that not every situation that an electrician will encounter will fit neatly into some code provision. I have a challenge for you sir. Describe an NEC compliant grounding electrode system for a radio relay equipment building on a rock solid ridge line were the deepest soil is less than six inches and the rest of the ridge is solid rock. I suppose that the copper ribbon conductors we installed right on the face of the rock until the ground impedance was less than ten ohms are a violation in your book. Up until now I would have said we did a good job of grounding that structure under very difficult circumstances. If the entire electrical industry accepted your position that we should use alternate methods "only when it is not possible to use what is listed and approved by the NEC" development of new methods would never occur. Your approach to enforcement of the NEC encourages the installation of ineffective minimum code compliant installations. The code isn't a cook book that provides recipes for good electrical installations. The NEC contains the following language on the codes purpose.
"90.1 Purpose.
(A) Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity."
How will your decision to reject an installation with a ground impedance of four ohms in favor of an installation with a ground impedance of eighty plus ohms serve the interest of practical safeguarding?
--
Tom
 
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Old 07-24-02, 01:36 PM
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This reply is confined to the question of the armor of armored cable not in compliance with Art 320.100 of the 2002 Code serving as an Equiptment Grounding Conductor.The basic question is this-to what extent should/could the 2002 Code be applied retro-actively? A related question is practicality-we all have encountered sitautions with old installations where a practical solution may not be in strict compliance with the NEC.----If an "old" armored cable must be rejected as an EGC because it does not comply with 320.100 then it must be rejected as a wiring means if the conductors do not comply with 320.104 which does not list type "R" conductors which are now obsolete but were the "standard" conductors used in armored cable.Which is more practical?-to leave an old,defective,badly-worn 2-prong receptacle in use or to replace it with a new Grounding-type receptacle where the existing Wiring Method is armored cable clamped/connected to metal outlet boxes?Why should it be presumed that "old" armored cable does not satisfy Art. 320.108, Equiptment Grounding?
 
  #19  
Old 07-24-02, 04:47 PM
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Patbaa,
In my opion existing wiring that met the NEC active at the original time it was installed is existing.

To change that two prong receptacle with a new two prong receptacle the NEC is accepting that original two wire cable.

When you change that two prong receptacle to a three prong receptacle the wiring will then come under the current code becuase you are required to create a grounding path where there was not a grounding path because of your replacing that two prong receptacle with a three prong receptacle where it was originally wired by a two prong receptacle without grounding.

When you create something in that existing branch circuit that was not a part of that original branch circuit then you must meet the current Code requirements to create that new entity. This would require today's code to recognize that grounding path as an approved grounding path accepted by the current code.

Nowhere in the Code was 3/8" metal jackets approved as a grounding path.

Do you have an older code back in that ara that listed 3/8" metal jackets to be used as a grounding path that I don't know of, or somewhere in the current code that accepts 3/8" metal jacket to be used as a grounding path that I am not aware of?

Hornted, it is obvious that we will gain nothing in a discussion as to how alternative methods should be approved. For sake of shortnening another abrasive discussion with you I am going to declare that we will have to again agree not to agree. You asked my opinion and I provided it, best I got, Sorry.

Curious

Wg
 
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Old 07-25-02, 07:57 AM
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not to beat a dead horse, but

Generic BX cable was being made before Listing and labeling was required. A company made it, early in the 1900s by Harry Greenfield and Gus Johnson who called their product BX cable. As A GENERIC term, (for AC cable.) Not until listing and labeling came along, it was required to be made with the bonding strip installed. The NEC does not recognize BX cable as an approved wiring method, because BX does not exist....
Knowing this, so called BX cable cannot be altered, repaired, or reused. Without being replaced. With an approved type of wiring method, and then meeting the requirements of there respected Article in the Code.
 
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Old 07-25-02, 11:46 AM
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WG; I infer that you dont' accept re-placing 2-prong receptacles with the 3-prong Grounding type where the wiring method is "old" armored cable without the bonding strip as required for new installations. I don't agree with applying the Code retro-actively on the Grounding quality of "old" armored cable and concluding that "old" armored cable cannot serve as an EGC simply because of the absence of a bonding strip.If you dis-approve of "old" armored cable as an EGC please allow me to suggest you cite Art. 320.108 which is NOT applying the Code retro-actively.----Cheers, Proud & Thankful---
 
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Old 07-25-02, 12:03 PM
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I don't think that Wg is saying any such thing. I think he is only saying that old BX cable does not fit the code definition of "armored cable" and never has. So all code references to AC don't apply to the earlier BX. I don't believe earlier BX cable has ever been an approved EGC, so I don't think Wg is retroactively applying the code. The assertion that BX is a trade name for AC is just not always true, despite the fact that it is commonly referred to as such.
 
  #23  
Old 07-25-02, 12:53 PM
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Glad to see some that can see what I have been trying to refer to concerning older style BX cable. Get lonely out there at times.

While I do not agree with the outlook that Patbaa and hornetd interpret, I do recongnize that these two holding their interpretation as they do are just a couple in a much larger crowd of people who also interpret the same way they do. Yet there are also just as great a number that interpret as I was referring to. I have seen the results of the 3/8 metal jacket having melt downs, weld marks the entire length of the cable, much damage and fires caused by this type of equipment grounidng use of the metal jacket as a grounding conductor over many years of experience. Many others have also seen this adverse results over the years also. Suspect htat is why no metal jacket of a 3/8" cable is allowed as a grounidng conductor in lengths over 6' today or in that last decade of Code versions.

The judgment criteria of the 3/8" metal jacket showing as a solid grounding path also could be related to the copper conductors laid in a trench and judge fine as a grounding electrode because it megged less that 25 ohms to ground. There is a lot of criteria that is not being taken into account on both subjects such as strength of that metal jacket holding and resistance in metal ribbon with its massive length creating an action of jumping wraps of that cable that was manufactured loosely wrapped inviting the arcing or a complete disintegration of the metal tape of that metal jacket when the fault is high enough and long enough in duration. As well the copper conductors laying in earth cna be exposed to major differences of soil type including corrosive and moiture differences that may deterritat that copper conductor. A second criteria is the alloy mix of the copper being used as a conductor buried in the earth. Is this copper pure copper, 60% copper with 40% tin mixed, etc. These criteria creates a nonsubstantial reliability question of this alternative grounding electrode method. Lack of years of testing to see what will be left of this conductor in that certain type soil a decade or so later is a concern. There are much to consider using alternative methods not recognized and approved by the NEC or listed and labeled for a certain use.

This is where I have reluctance to accept unsubstantiated alternative wiring products or methods. There is way much that needs to be considered when using alternative methods not mentioning the risk of liability involved if something was missed. If the NEC which is widely accepted as a minimum safety standard does not list, approve, etc. this alternative wiring method then much substantiation should be provided and recorded.

It is not now nor ever was my intent to block the inovative use of new products on the market. It is my intent to require the needed documentation proving the reliability and safety of an alternative wiring method in order for the electircal industry to accept that alternatvie wiring method.

Just because we don't understand why the NEC did not approve a certain product of wiring method does not mean the NEC is wrong.

Just because the NEC has not approved a certain product of wiring method also does not mean that when that product has been proven by accepted track records and testing means in the industry that the NEC will not accept it in the future.

Making our own rules as we go to meet what we think is right regardless of Code rules or making ourselves invention experts without complete and detailed substantiation by accepted means in the industry is dangerous to all in my opinion.

Patbaa, you are only one of many that beleive old BX cable should be accepted as a grounding path. I have seen a large crowd over the years that believe the same as you.

With the experiences and training I have had or seen in the field over many years I just disagree with your thoughts on this 3/8" metal jacket being safe or accepted by the NEC, today, or even back when it was originally installed as a grounding path.

just my opinion !

Wg
 
  #24  
Old 07-26-02, 07:42 AM
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Originally posted by Wgoodrich
Glad to see some that can see what I have been trying to refer to concerning older style BX cable. Get lonely out there at times.

While I do not agree with the outlook that Patbaa and hornetd interpret, I do recognize that these two holding their interpretation as they do are just a couple in a much larger crowd of people who also interpret the same way they do. Yet there are also just as great a number that interpret as I was referring to. I have seen the results of the 3/8 metal jacket having melt downs, weld marks the entire length of the cable, much damage and fires caused by this type of equipment grounding use of the metal jacket as a grounding conductor over many years of experience. Many others have also seen this adverse results over the years also. Suspect that is why no metal jacket of a 3/8" cable is allowed as a grounding conductor in lengths over 6' today or in that last decade of Code versions.
You know I don't see how this badgering the topic is the same as "agreeing to disagree."

I have never suggested the use of the armor of older BX cable as an Equipment Grounding Conductor without the approval of the authority having jurisdiction.

The judgment criteria of the 3/8" metal jacket showing as a solid grounding path also could be related to the copper conductors laid in a trench and judge fine as a grounding electrode because it megged less that 25 ohms to ground. There is a lot of criteria that is not being taken into account on both subjects such as strength of that metal jacket holding and resistance in metal ribbon with its massive length creating an action of jumping wraps of that cable that was manufactured loosely wrapped inviting the arcing or a complete disintegration of the metal tape of that metal jacket when the fault is high enough and long enough in duration. As well the copper conductors laying in earth can be exposed to major differences of soil type including corrosive and moisture differences that may deteriorate that copper conductor. A second criteria is the alloy mix of the copper being used as a conductor buried in the earth. Is this copper pure copper, 60% copper with 40% tin mixed, etc. These criteria creates a non substantial reliability question of this alternative grounding electrode method. Lack of years of testing to see what will be left of this conductor in that certain type soil a decade or so later is a concern. There are much to consider using alternative methods not recognized and approved by the NEC or listed and labeled for a certain use.
For someone who has been insisting on the use of correct technique your use of the term "megged" is surprising. The use of "meggers" to test the impedance of grounding electrodes of any kind will yield erroneous results. The only instruments acceptable for use in testing the impedance of grounding electrodes are the clamp on inductive coupling type of ground impedance testers or the three and four pole fall of potential ground impedance test instruments.
If the number two copper conductor might fail due to corrosive conditions then how on earth could that same conductor be suitable for use as a ground ring. Buildings vary in size from well houses and guard shacks to the monster multi acre warehouses now seen in the retailing business. That is why the US NEC© prescribes a minimum length for the ground ring conductor. The distance across a small single family home could put you into a completely different soil type. Every time a ground ring is constructed the number two copper conductor that is used as the electrode is subject to any deteriorating conditions present in the soil. How does running the conductor in a trench around the building change the likelihood of electrode corrosion. You have already indicated that the use of listed ground rods buried in the same trench is acceptable. Are galvanized steel ground rods not available in your portion of the world? Do you expect those listed and labeled ground rods to stand up to any corrosion better than copper wire? As for your supposed wire made of a copper tin alloy who here suggested using anything but copper? All copper conductors manufactured in the US are gauged prior to the application of any tinning. This is obviously a red herring to distract from and obfuscate the real issue which you have declined to address. How will your decision to reject an installation with a ground impedance of four ohms in favor of an installation with a ground impedance of eighty plus ohms serve the interest of practical safeguarding?

This is where I have reluctance to accept unsubstantiated alternative wiring products or methods. There is way much that needs to be considered when using alternative methods not mentioning the risk of liability involved if something was missed. If the NEC which is widely accepted as a minimum safety standard does not list, approve, etc. this alternative wiring method then much substantiation should be provided and recorded.

It is not now nor ever was my intent to block the innovative use of new products on the market. It is my intent to require the needed documentation proving the reliability and safety of an alternative wiring method in order for the electrical industry to accept that alternative wiring method.

Just because we don't understand why the NEC did not approve a certain product of wiring method does not mean the NEC is wrong.

Just because the NEC has not approved a certain product of wiring method also does not mean that when that product has been proven by accepted track records and testing means in the industry that the NEC will not accept it in the future.

Making our own rules as we go to meet what we think is right regardless of Code rules or making ourselves invention experts without complete and detailed substantiation by accepted means in the industry is dangerous to all in my opinion.
The NFPA does not "List" or "approve" anything. What it does do is to permit the Authority Having Jurisdiction (AHJ) to approve alternative methods or materials based on a set of criteria listed in the National Electric Code©. You keep insisting that if it is not already in the NEC© it could not possibly be a safe methodology. If you look back at older additions of the NEC you will find that many wiring methods and materials we use today were not anticipated by those documents. How then did they end up in accepted use? They were developed and proved by field practitioners at places quite remote from Batterymarch Park in Quincy, Massachusetts. [The present headquarters of the NFPA] The method of grounding receptacles supplied by BX cable by running a separate conductor back to the grounding electrode system that you have already indicated is the correct way to do it was developed by the US Army Corps of Engineers and the US Air Force Ground Electronic Engineering and Installation Agency. During those same test some installations of BX cable were found to have an acceptable ground impedance using the jacket of the cable as the Equipment Grounding Conductor. Those test were actually executed by electricians rather than by engineers as you seem to assume. I know because I was a nineteen year old airman who participated at the time in running those test. If you think for one minute that those officer and gentleman engineers crawled around under old buildings running and testing the proposed grounding method; that you swear by because it is written down in the NEC©; then you are delusional. The separate conductor method of grounding made it into the US Air Force standards for electrical installations; and later into the US NEC©; because it was found to be suitable for general application by electricians in the field without access to expensive testing equipment. The other method that was evaluated during the same testing was an application of the National Board of Fire Underwriters (NBFU) test for grounding effectiveness to existing BX cable installations. Nearly a third of BX cable installations were found to provide an equipment grounding pathway that was less than or equal to the impedance of the additional conductor. Neither method provided a low enough impedance to reliably clear a ground fault and that fact has not changed. What the additional conductor method and the tested jacket method did was reduce the touch potential of connected equipment to a much safer level during a fault to the conductive metal case. The actual application of the tested jacket method is beyond the scope of a DIY forum and describing it here would be a disservice because some unqualified person might attempt it and derive a false sense of security form the possibly erroneous results.

Patbaa, you are only one of many that believe old BX cable should be accepted as a grounding path. I have seen a large crowd over the years that believe the same as you.

With the experiences and training I have had or seen in the field over many years I just disagree with your thoughts on this 3/8" metal jacket being safe or accepted by the NEC, today, or even back when it was originally installed as a grounding path.

Just my opinion !

Wg [/B]
If you are including me in the proponents of using untested BX cable jackets as a grounding path than you are doing me a disservice and I cannot imagine what I could have done to so completely offend you that you would malign me in this way. Let me ask you point blank if you are one of those people that once someone disagrees with you continually looks for some opportunity to prove them wrong and even resorts to distortion of their position to accomplish that?
--
Tom
 
  #25  
Old 07-26-02, 08:00 AM
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Ok, Don't you guys own a television? LOL Just kidding!!

I see that there are a lot of references to the Authority Having Jurisidiction. If we take that route, the AHJ will ask for specific evidence as to the intended use. Could someone tell me where I could get that info to give to the inspector?
 
  #26  
Old 07-26-02, 10:05 AM
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John Nelson; if the Wiring Method that was installed in a residence in 1930 is a factory assembly of insulated conductors enclosed in a flexible metal sheath,then it's Armored Cable.----At what date does such a Wiring Method as described qualify as Armored Cable, if not in 1930?-----WG,when you mention the effects of Ground-Fault currents on Armored Cable, please consider the possibility of a circuit-breaker that fails to "trip",and that a large Ground-Fault current implies a LOW resistance to Ground. I guess that "old" Armored Cable had less resistance because of a larger diameter.Correct me if I'm wrong but the only difference I perceive between "old" and "acceptable" is a very small diameter bonding strip.I repeat, your opposition to "old" Armored Cable is best sustained by citing Art. 320.108.-----HS----A customer installs a 7.5 amp window A.C. unit and needs a 3-prong receptacle. The Wiring Method is "old" AC and the conductors do not comply with Art 320.104. I measure 120 volts across the old receptacle(no load) and then measure 118 volts with the A.C. unit operating "hot" to Ground which means a 2-volt drop in the cable armor.Do I (1) connect a 3-prong receptacle-(2) operate the A.C.on the old receptacle with a cord-plug adapter-or (3) snip off the Ground prong off the cord-plug?---Cheers, P&T
 
  #27  
Old 07-26-02, 02:35 PM
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LOAD TESTING OF GROUNDS.

Originally posted by PATTBAA
John Nelson; if the Wiring Method that was installed in a residence in 1930 is a factory assembly of insulated conductors enclosed in a flexible metal sheath, then it's Armored Cable.
I will have to disagree with that statement. Armored cable has a code definition that the old BX cable cannot meet.
320.100 Construction.
Type AC cable shall have an armor of flexible metal tape and shall have an internal bonding strip of copper or aluminum in intimate contact with the armor for its entire length.
It is the presence of the internal bonding strip that makes it armored cable instead of BX.

At what date does such a Wiring Method as described qualify as Armored Cable, if not in 1930?----- WG, when you mention the effects of Ground-Fault currents on Armored Cable, please consider the possibility of a circuit-breaker that fails to "trip", and that a large Ground-Fault current implies a LOW resistance to Ground. I guess that "old" Armored Cable had less resistance because of a larger diameter. Correct me if I'm wrong but the only difference I perceive between "old" and "acceptable" is a very small diameter bonding strip. I repeat, your opposition to "old" Armored Cable is best sustained by citing Art. 320.108. HS A customer installs a 7.5 amp window A.C. unit and needs a 3 prong receptacle. The Wiring Method is "old" AC and the conductors do not comply with Art 320.104. I measure 120 volts across the old receptacle (no load) and then measure 118 volts with the A.C. unit operating "hot" to Ground which means a 2 volt drop in the cable armor. Do I (1) connect a 3 prong receptacle- (2) operate the A.C. on the old receptacle with a cord plug adapter or (3) snip off the Ground prong off the cord plug? Cheers, P&T
How about college level answer D for none of the above. If you do not have the use of the equipment necessary to test the impedance of the grounding conductor pathway in a manor consistent with the fault current available then you should install one of the 406.3 (d) (3) replacement receptacles. In the case of BX cable you would want to install a GFI breaker or upstream receptacle. It is my personal opinion that GFI receptacles should not be used to protect outlets that are not insight from the GFI mechanism. With a heavy draw appliance such as a window air conditioner the addition of a separate equipment grounding conductor to the circuit will assure prompt tripping of the GFI at the moment a case to ungrounded conductor fault occurs. If you have the measuring equipment and training necessary to testing the impedance of the EGC path through the cable armor then you would submit the results of that test to the AHJ and seek her/his approval for the use of that pathway. Neither grounding method is likely to provide a low enough impedance to clear a fault in time to prevent dangerous heating without the addition of GFI protection. GFI protection alone is code compliant but still leaves the hazards associated with the shock received during it's tripping. The normal human reactions to the brief shock can result in dangerous falls or other struck by or collided with type injuries.
--
Tom
 
  #28  
Old 07-26-02, 07:31 PM
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Copied section of NEC 2002 pertaining to the 8 things pertaining to evaluation of equipment;

110.3 Examination, Identification, Installation, and Use of Equipment.
(A) Examination. In judging equipment, considerations such as the following shall be evaluated:
(1) Suitability for installation and use in conformity with the provisions of this Code
FPN:Suitability of equipment use may be identified by a description marked on or provided with a product to identify the suitability of the product for a specific purpose, environment, or application. Suitability of equipment may be evidenced by listing or labeling.
(2) Mechanical strength and durability, including, for parts designed to enclose and protect other equipment, the adequacy of the protection thus provided
(3) Wire-bending and connection space
(4) Electrical insulation
(5) Heating effects under normal conditions of use and also under abnormal conditions likely to arise in service
(6) Arcing effects
(7) Classification by type, size, voltage, current capacity, and specific use
(8) Other factors that contribute to the practical safeguarding of persons using or likely to come in contact with the equipment

(B) Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

COPIED SECTION OF 2002 HANDBOOK COMMENTARY;

Manufacturers usually supply installation instructions with equipment for use by general contractors, erectors, electrical contractors, electrical inspectors, and others concerned with an installation. It is important to follow the listing or labeling installation instructions. For example, 210.52, second paragraph, permits permanently installed electric baseboard heaters to be equipped with receptacle outlets that meet the requirements for the wall space utilized by such heaters. The installation instructions for such permanent baseboard heaters indicate that these heaters should not be mounted beneath a receptacle. In dwelling units, it is common to use low-density heating units that measure in excess of 12 ft in length. Therefore, to meet the provisions of 210.52(A) and also the installation instructions, a receptacle must either be part of the heating unit or be installed in the floor close to the wall but not above the heating unit. (See 210.52, FPN, and Exhibit 210.23 for more specific details.)
In itself, 110.3 does not require listing or labeling of equipment. It does, however, require considerable evaluation of equipment. Section 110.2 requires that equipment be acceptable only if approved. The term approved is defined in Article 100 as acceptable to the authority having jurisdiction. Before issuing approval, the authority having jurisdiction (also defined in Article 100) may require evidence of compliance with 110.3(A). The most common form of this evidence considered acceptable by authorities having jurisdiction is a listing or labeling by a third party.
Some sections in the Code require listed or labeled equipment, such as 250.8, which includes the phrase “listed pressure connectors, listed clamps, or other listed means.”

COMMENT

It was asked to provide the list of criteria to give to their inspector the above contains the rules in the NEC 2002 that is being discussed.

COPIED SECTION OF 2002 NEC;

250.50 Grounding Electrode System.
If available on the premises at each building or structure served, each item in 250.52(A)(1) through (A)(6) shall be bonded together to form the grounding electrode system. Where none of these electrodes are available, one or more of the electrodes specified in 250.52(A)(4) through (A)(7) shall be installed and used.


COMMENTARY;
If the rule in 250.50 is read as worded there is no option to use any other alternative grounding electrode as a sole grounding electrode. Rule 250.50 states that where none of those elctrodes listed in 250.50 is available then one or moer of the electrodes specified in 250.52.A4 through A7 must be installed to serve as the grounding electrode.

COPIED SECTION OF 250.52.A.4 THROUGH A7;

(4) Ground Ring. A ground ring encircling the building or structure, in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG.
(5) Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.5 m (8 ft) in length and shall consist of the following materials.
(a) Electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3/4) and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.
(b) Electrodes of rods of iron or steel shall be at least 15.87 mm (5/8 in.) in diameter. Stainless steel rods less than 16 mm (5/8 in.) in diameter, nonferrous rods, or their equivalent shall be listed and shall not be less than 13 mm (1/2 in.) in diameter.
(6) Plate Electrodes. Each plate electrode shall expose not less than 0.186 m2 (2 ft2) of surface to exterior soil. Electrodes of iron or steel plates shall be at least 6.4 mm (1/4 in.) in thickness. Electrodes of nonferrous metal shall be at least 1.5 mm (0.06 in.) in thickness.
(7) Other Local Metal Underground Systems or Structures. Other local metal underground systems or structures such as piping systems and underground tanks.

COMMENTARY;

Take special attention to 250.52.A.4 concerning grounidng ring that is being mentioned concerning the 20' in length minimum. Notice that this grounding ring must be located encircling the structure in direct contact with the earth.

This 250.52.A.4 does not include a trench heading away from the building to a well becuase that trench is not encircling the building. It is my belief that the encircling the structure is required do to the fact that encircling the building has a tendency to stay wet near the foundation of that building year around.

The discussion in this thread seems to be centered on proper use of the powers issued to an AHJ in approving a product or installation that is not recognized in the NEC and the methods used by the AHJ in approving what is not recognized by the NEC.

Wg
 
  #29  
Old 07-27-02, 09:58 PM
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Originally posted by Wgoodrich

Huge Snip

COMMENTARY;

Take special attention to 250.52.A.4 concerning grounidng ring that is being mentioned concerning the 20' in length minimum. Notice that this grounding ring must be located encircling the structure in direct contact with the earth.

This 250.52.A.4 does not include a trench heading away from the building to a well becuase that trench is not encircling the building. It is my belief that the encircling the structure is required do to the fact that encircling the building has a tendency to stay wet near the foundation of that building year around.

The discussion in this thread seems to be centered on proper use of the powers issued to an AHJ in approving a product or installation that is not recognized in the NEC and the methods used by the AHJ in approving what is not recognized by the NEC.

Wg
So you have found some language in the NEC that requires the ground ring to be in some particular proximity to the building in order to take advantage of the moisture you ASS/U/ME will be there or are you grasping at straws? If the building has been built with a footer drainage system the soil adjacent to the building will be dryer not wetter than the soil some distance away. In island and some rural installations roof run off is carefully collected to be used and is not allowed to drain into the soil. A ground ring only has to encircle the building. That circle can be as large as the installers inclination and equipment permit. You may also want to note that the ring does not have to be effectively closed. The end of the number two copper is not required to be connected back into the GEC or the first portion of the ground ring. The original idea behind the use of ground rings was the theory that they would reduce the touch potential of the buildings grounded systems during a lightning strike or high voltage fault. Trouble is that research done by Consolidated Edison of Chicago back in the mid fifties demonstrated that ground rings were ineffective at reducing touch potential. The only effective technique for reducing touch potential is a true UFER ground were all of the reinforcing steel for the concrete footer and floor is carefully tied and then connected to the neutral. The reason ground rings continue in use is that they provide the lowest impedance to earth in shallow soils for buildings that do not use concrete foundations.

I guess I will just have to throw the two ground rods into the trench with the number two then you can sign the sticker with a clear conscience. But if you think that will make one ohm of difference electrically then you must see some sort of magic that hews to compliance with the letter rather than the spirit of the code.
--
Tom
 
  #30  
Old 07-28-02, 07:43 AM
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tonyi
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Re: pvc grounding

"BX", if it has a bond wire in the armor, is an AC [armor clad] type cable - the armor is suitable for equipment ground. Unless someone screwed up with a splice or other box between here and the panel, your armor is a good ground. The code allows AC with a plastic box *IF* there are internal or integrated bonding means in the box [article 314.3 exceptions #1 and #2]. That you're asking this question suggests the box you have does NOT have this. If its some ordinary Home Depot Carlon box, it certainly does not have this capability and would be a code violation.

Is there some compelling reason not to use a metal box here?

Originally posted by jasontv8
I am looking for a way to ground 40 year old 2 wire bx in a plastic box. Can I use a metal clamp around the cable and ground to outlet or should I use GFI??
 

Last edited by tonyi; 07-28-02 at 08:47 AM.
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Old 07-28-02, 07:52 AM
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40 year old "BX" will undoubtedly have the bond wire and most likely plastic insulated conductors, something from the 20's or 30's might not.

My house was completely rewired in the early 60's with BX - plastic insulation and bond wire are there.
 
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Old 07-29-02, 08:57 AM
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hornetd: you are applying the 2002 Code retro-actively.According to your reasoning,as soon as the Code required a bonding strip for Armored Cable,existing Armored Cable was no longer Armored Cable-it became "BX" which is a "Trade-Name" and the NEC has never used Trade-names such as "Romex","Wiremold","Greenfield" etc.----How can a GFI receptacle be connected to "old B.X." without using the armor as an Equiptment Grounding Conductor? The devise screws bond the devise yoke to the metal and the Ground device terminal must connect to Ground.
 
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Old 07-29-02, 01:33 PM
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Presumably, a functioning GFCI will trip long before any sort of ground fault gets to the point where its going to torch the cable.

In a metal box, where connectors are tight, it would indeed be difficult to put in a GFCI that wasn't "grounded" even if old BX with no bond wire.

What I've been doing is putting in AFCI's *and* GFCI's when I'm leaving some old stuff in place. Hard to go wrong with that combination.

Originally posted by PATTBAA
...How can a GFI receptacle be connected to "old B.X." without using the armor as an Equiptment Grounding Conductor? The devise screws bond the devise yoke to the metal and the Ground device terminal must connect to Ground.
 
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Old 07-30-02, 01:06 PM
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Originally posted by PATTBAA
hornetd: you are applying the 2002 Code retro-actively.According to your reasoning,as soon as the Code required a bonding strip for Armored Cable,existing Armored Cable was no longer Armored Cable-it became "BX" which is a "Trade-Name" and the NEC has never used Trade-names such as "Romex","Wiremold","Greenfield" etc.----How can a GFI receptacle be connected to "old B.X." without using the armor as an Equiptment Grounding Conductor? The devise screws bond the devise yoke to the metal and the Ground device terminal must connect to Ground.
I am not applying the nec retroactively. I am applying it to the replacement receptacle we were talking about here and now. Since the existing cable is not armored cable under the present edition of the NEC you would need to provide a code compliant Equipment Grounding Conductor or make use of the code language that permits GFI receptacles as replacements. It would appear that you are trying to say that since that cable may have been described by the NEC at the time of manufacture as armored cable that it somehow complies with later requirements of the NEC for the construction of armor cable even though the code language has been changed to require a bonding strip in that type of cable.

So what I am saying is that the existing cable without a bonding strip is not a grounding method under the 2002 NEC.
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Old 07-31-02, 08:18 AM
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Hornetd; I definitely AM NOT contending that Armored Cable manufactured in 1950,for example, complies with the present Code.I AM contending that it's Armored Cable,with or without the bonding strip. If it's NOT Armored Cable ,circa 1950 or 1940,exactly what type of Wiring Method is it?--If you want to state that it's Armored Cable that does not comply with the 2002 Code,fine. The basic question is whether or not 1950 Armored Cable meets the requirement of 320.108, Equiptment Grounding. Anyone with doubts about Grounding with "old" Armored Cable is wecome to cite this particular Article.It is my opinion that Art 32.100,Construction, which applies to all NEW wiring, does not completely invalidate all previous installations of Armored Cable in terms of Grounding.----Cheers To All, P&T
 
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Old 07-31-02, 08:40 AM
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Originally posted by PATTBAA
Hornetd; I definitely AM NOT contending that Armored Cable manufactured in 1950,for example, complies with the present Code.I AM contending that it's Armored Cable,with or without the bonding strip. If it's NOT Armored Cable ,circa 1950 or 1940,exactly what type of Wiring Method is it?--If you want to state that it's Armored Cable that does not comply with the 2002 Code,fine. The basic question is whether or not 1950 Armored Cable meets the requirement of 320.108, Equiptment Grounding. Anyone with doubts about Grounding with "old" Armored Cable is wecome to cite this particular Article.It is my opinion that Art 32.100,Construction, which applies to all NEW wiring, does not completely invalidate all previous installations of Armored Cable in terms of Grounding.----Cheers To All, P&T

It is that very contention that I am disagreeing with. The additions of the code that described the previous constructions of armored cable did not describe it as an Equipment Grounding Conductor. It was only in responce to the code change that required an EGC to be run wih circuits that the construction of the cable was changed to lower the impedance of the armor to make i suitable as an EGC. The best way to think of "BX" cable is as an older form of metal clad cable (type MC). It does not have an EGC built in to the armor or cable jacket. Perhaps you would be willing to support your contenion that the code ever permited the unbonded armor of the oler version of that cable by sighting an addition of the code that required an EGC to be run with the circuit and also in the same addition recognized the armor as an EGC.
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Old 07-31-02, 10:54 AM
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We have stressed Grounding receptacles and "old" Armored Cable but we all have over-looked metal outlet boxes which are required to be Grounded as are ALL metal surfaces that enclose electrical wiring.-----If the armor of armored cable without an internal bonding strip is not acceptable as an Equitpment Grounding Conductor then all metal outllet boxes wired with this "old" type of amored cable are not Grounded and NEVER were Grounded.---or were they Grounded "then" but not Grounded "now", i.e., when the Code required the bonding strip?-Or is "old" armored cable suitable for Grounding outlet boxes but not receptacles? And if so,why. Comments and Explanations Welcome.---
 
  #38  
Old 07-31-02, 02:09 PM
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Same situation applies to the old cloth bound 2-wire NM and K&T. All that stuff went into ungrounded metal boxes. Existing installations don't become magically illegal though because code at the time allowed it. It would be prudent to fit GFCI's though even if keeping the old 2-prong receptacles.

Originally posted by PATTBAA
...but we all have over-looked metal outlet boxes...
 
  #39  
Old 07-31-02, 02:24 PM
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250.86

While the older BX cable metal jacket was not approved as an equipment grounding conductor that metal jacket if installed right originally was grounded. As far as I can sort it out the metal jacket of the older two wire BX cable, if it was connected to the panel properly on original installation was bonded to the panel at the beginning of that metal jacket where it connects to the panel if it was or is a grounded electrical system at the panel. If the house is original and a two wire nongrounded service it is still recognized under the Code version at the time of original installation. If it is untouched and original and accepted by the NEC at the time of original installation then it is still governed under that older NEC version that did not require a grouded system.

This would put our concern being of bonding metal boxes. Check Exception 2 below. I included all the exceptions but I suspect exception 2 would answer the metal box grounding question of a two wire BX cable installed years ago or an extension added to that existing two wire BX cable if installed now. The exception should show that metal box is omitted from teh grounding requirment.

COPIED SECTION 250.86 in 2002 NEC;

Exception No. 1: Metal enclosures and raceways for conductors added to existing installations of open wire, knob and tube wiring, and nonmetallic-sheathed cable shall not be required to be grounded where these enclosures or wiring methods
(a) Do not provide an equipment ground;
(b) Are in runs of less than 7.5 m (25 ft);
(c) Are free from probable contact with ground, grounded metal, metal lath, or other conductive material; and
(d) Are guarded against contact by persons.

Exception No. 2: Short sections of metal enclosures or raceways used to provide support or protection of cable assemblies from physical damage shall not be required to be grounded.

Exception No. 3: A metal elbow shall not be required to be grounded where it is installed in a nonmetallic raceway and is isolated from possible contact by a minimum cover of 450 mm (18 in.) to any part of the elbow or is encased in not less than 50 mm (2 in.) of concrete.

hope this helps

Wg
 
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Old 08-01-02, 07:12 AM
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If it is argued that in 1950 (for example) the NEC accepted armored cable as an approved Wiring Method but did not accept the cable armor as an Equiptment Grounding Conductor,then obviously the NEC was allowing the use of un-grounded metal outlet boxes.I believe this argument is absurd.There were 2 inherent features in armored cable when it came into use-protection against mechanical injury and a Grounding path.I repeat-the "Construction" Article in the present Code does not automaticaly invalidate all previous usage of armored cable as an EGC.----WG, please allow me to state that the 3 exceptions you mention are in my opinion irrelevent to the issue of Grounding metal outlet boxes with armored cable.. Armored Cable is neither an enclosure or a raceway.---Thanks to All--P&B
 
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