follow-up for wgoodrich...

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  #1  
Old 05-23-01, 05:37 PM
edbreyer
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Thanks for the clarification regarding b/x versus metal clad and AC cable. I have a couple follow-up questions:

> Does the short run limitation you mentioned previously also apply to metal clad, AC cable and greenfield?

> If so, what are your thoughts on these products compare to Romex in terms of safety? Again, I can't imagine armored cable isn't at least as safe as romex - so why a length limitation on it but not Romex? Am I missing an important issue/consideration?

> Does greenfield have a typical outside diameter that will help me identify it (or is that the greater than 3/8" that you mentioned previously)? OR, do I just look to see if the armored cable has standard t/w wire without the paper wrap, etc.?

> Assuning I find greenfield in my house - and want to replace the older wire - will fishtape pull through greenfield without snagging or is it more trouble than it's worth?

Thanks for taking the time to educate me - I really appreciate getting feedback from a knowledgable professional.

Ed
 
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  #2  
Old 05-24-01, 12:44 PM
Wgoodrich
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ARTICLE 333 -- Armored Cable: Type AC
A. General
333-1. Definition
Type AC cable is a fabricated assembly of insulated conductors in a flexible metallic enclosure. See Section 333-19.
333-2. Other Articles
Type AC cable shall comply with this article and also with the applicable provisions of other articles in this Code, especially Article 300.
333-3. Uses Permitted
Except where otherwise specified in this Code and where not subject to physical damage, Type AC cable shall be permitted for branch circuits and feeders in both exposed and concealed work and in cable trays where identified for such use.
Type AC cable shall be permitted in dry locations and embedded in plaster finish on brick or other masonry, except in damp or wet locations. It shall be permissible to run or fish this cable in the air voids of masonry block or tile walls where such walls are not exposed or subject to excessive moisture or dampness.
333-4. Uses Not Permitted
Type AC cable shall not be used where prohibited elsewhere in this Code, including the following:
1. In theaters and similar locations, except as provided in
Article 518, Places of Assembly
2. In motion picture studios
3. In any hazardous (classified) location except as permitted by Sections 501-4(b), Exception, 502-4(b), Exception No. 1, and 504-20
4. Where exposed to corrosive fumes or vapors
5. On cranes or hoists, except as provided in Section 610-11(c)
6. In storage battery rooms
7. In hoistways or on elevators, except as provided in Section 620-21
8. In commercial garages where prohibited in Article 511

More to come

Wg
 
  #3  
Old 05-25-01, 01:20 PM
Wgoodrich
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Metal Clad

334-1. Definition
Type MC cable is a factory assembly of one or more insulated circuit conductors with or without optical fiber members enclosed in an armor of interlocking metal tape, or a smooth or corrugated metallic sheath.
334-2. Other Articles
Metal-clad cable shall comply with this article and also with the applicable provisions of other articles in this Code, especially Article 300.
Type MC cable shall be permitted for systems in excess of 600 volts, nominal. See Section 300-2(a).
334-3. Uses Permitted
Unless specifically prohibited elsewhere in this Code and where not subject to physical damage, Type MC cables shall be permitted as follows:
1. For services, feeders, and branch circuits
2. For power, lighting, control, and signal circuits
3. Indoors or outdoors
4. Where exposed or concealed
5. Direct buried where identified for such use
6. In cable tray
7. In any raceway
8. As open runs of cable
9. As aerial cable on a messenger
10. In hazardous (classified) locations as permitted in Articles 501, 502, 503, 504, and 505
11. In dry locations and embedded in plaster finish on brick or other masonry except in damp or wet locations
12. In wet locations where any of the following conditions are met:
a. The metallic covering is impervious to moisture.
b. A lead sheath or moisture-impervious jacket is provided under the metal covering.
c. The insulated conductors under the metallic covering are listed for use in wet locations.
334-4. Uses Not Permitted
Type MC cable shall not be used where exposed to destructive corrosive conditions, such as direct burial in the earth, in concrete, or where exposed to cinder fills, strong chlorides, caustic alkalis, or vapors of chlorine or of hydrochloric acids, unless the metallic sheath is suitable for the conditions or is protected by material suitable for the conditions.
 
  #4  
Old 05-25-01, 01:32 PM
Wgoodrich
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Nonmetallic sheathed cable is often called Romex. Cloth style Romex was approved for inside a structure in a dry location and is usually much older style Romex with 60 degree C. type TW conductors in the cable usually found to be installed prior to approximately 1963. Cloth style Romex is no longer manufactured but is still approved to be used as existing installations. Type NM is usually approved for inside a sturcture in a dry location and is usually an older style Romex with 60 degree C. type TW conductors in the cable, usually found installed before 1988. Type NM cable is no longer manufactured. Type NMB cable [Romex] is the newest style Romex or nonmetallic sheathed cable manufactured on todays market and currently being used. Type NMB cable appeared on the market post 1988 and inside this type NMB cable you will find type THHN conductors rated 90 degree C. This higher rated wire was in answer to much hotter attics found in souther States of the US. These attics with much higher ambient temperature averages caused a conflict in ampacity ratings when type NM Romex was installed in those attics. The results was the manufacturing and UL and NEC change in the design by replacing the 60 degree C type TW. conductors with 90 degree C type THHN conductors installed within this type NMB Cable. See below on acceptable uses;

ARTICLE 336 -- Nonmetallic-Sheathed Cable: Types NM, NMC, and NMS
336-1. Scope
This article covers the use, installation, and construction specifications of nonmetallic-sheathed cable.
A. General
336-2. Definition
Nonmetallic-sheathed cable is a factory assembly of two or more insulated conductors having an outer sheath of moisture-resistant, flame-retardant, nonmetallic material.
336-3. Other Articles
Installations of nonmetallic-sheathed cable shall comply with the other applicable provisions of this Code, especially Articles 300 and 310.
336-4. Uses Permitted
Type NM, Type NMC, and Type NMS cables shall be permitted to be used in the following:
1. One- and two-family dwellings
2. Multifamily dwellings and other structures, except as prohibited in Section 336-5
3. Cable trays, where the cables are identified for the use
FPN: See Section 310-10 for temperature limitation of conductors.
(a) Type NM. Type NM cable shall be permitted for both exposed and concealed work in normally dry locations. It shall be permissible to install or fish Type NM cable in air voids in masonry block or tile walls where such walls are not exposed or subject to excessive moisture or dampness.
(b) Type NMC. Type NMC cable shall be permitted as follows:
1. For both exposed and concealed work in dry, moist, damp, or corrosive locations
2. In outside and inside walls of masonry block or tile
3. In a shallow chase in masonry, concrete, or adobe protected against nails or screws by a steel plate at least 1/16-in. (1.59-mm) thick, and covered with plaster, adobe, or similar finish
(c) Type NMS. Type NMS cable shall be permitted for both exposed and concealed work in normally dry locations. It shall be permissible to install or fish Type NMS cable in air voids in masonry block or tile walls where such walls are not exposed or subject to excessive moisture or dampness. Type NMS cable shall be used as permitted in Article 780.
336-5. Uses Not Permitted
(a) Types NM, NMC, and NMS. Types NM, NMC, and NMS cables shall not be used in the following:
1. In any multifamily dwelling or other structure exceeding three floors above grade
For the purpose of this article, the first floor of a building shall be that floor that has 50 percent or more of the exterior wall surface area level with or above finished grade. One additional level that is the first level and not designed for human habitation and used only for vehicle parking, storage, or similar use shall be permitted.
2. As service-entrance cable
3. In commercial garages having hazardous (classified) locations as provided in Section 511-3
4. In theaters and similar locations, except as provided in Article 518, Places of Assembly
5. In motion picture studios
6. In storage battery rooms
7. In hoistways
8. Embedded in poured cement, concrete, or aggregate
9. In any hazardous (classified) location, except as permitted by Sections 501-4(b), Exception, 502-4(b), Exception, and 504-20
(b) Types NM and NMS. Types NM and NMS cable shall not be installed in the following:
1. Where exposed to corrosive fumes or vapors
2. Where embedded in masonry, concrete, adobe, fill, or plaster
3. In a shallow chase in masonry, concrete, or adobe and covered with plaster, adobe, or similar finish
 
  #5  
Old 05-25-01, 01:43 PM
Wgoodrich
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What you are calling FLEX is only an empty flexible metal conduit. The 6' limitations only apply to smaller than 1/2". The older type BX cable you talked of is 3/8" in diameter. The previous reply explaining use of Metal clad is the product that replaced type BX cable. Premanufactured BX cable [no longer manufactured and the newer metal clad cable and / or type AC cable are both premanufactured in a factory. The wires exist inside the 3/8" flex of this type MC or type AC cable before the cable is installed. Other words the cable is made over the existing conductors in the factory. No 3/8" flexible conduit is designed to install new conductors inside that existing 3/8" flex. Damage most likely will occur causing hazards of shock or fire. This is why the limitation of the use of 3/8" cable to 6' which seems to limit damage to conductors while fishing wires into it. See Article 350-10-A below;

ARTICLE 350 -- Flexible Metal Conduit
A. General
350-1. Scope
This article covers the use and installation of flexible metal conduit and associated fittings.
350-2. Definition
Flexible metal conduit is a raceway of circular cross section made of helically wound, formed, interlocked metal strip.
350-3. Other Articles
Installations of flexible metal conduit shall comply with the applicable provisions of Article 300.
350-4. Uses Permitted
Flexible metal conduit shall be listed and shall be permitted to be used in exposed and concealed locations.
350-5. Uses Not Permitted
Flexible metal conduit shall not be used in the following:
1. In wet locations unless the conductors are approved for the specific conditions and the installation is such that liquid is not likely to enter raceways or enclosures to which the conduit is connected
2. In hoistways, other than as permitted in Section 620-21(a)(1)
3. In storage-battery rooms
4. In any hazardous (classified) location other than as permitted in Sections 501-4(b) and 504-20
5. Where exposed to materials having a deteriorating effect on the installed conductors, such as oil or gasoline
6. Underground or embedded in poured concrete or aggregate
7. Where subject to physical damage
B. Installation
350-10. Size
(a) Minimum. Flexible metal conduit less than -in. electrical trade size shall not be used unless permitted in (1) through (5) below for 3/8-in. electrical trade size.
1. For enclosing the leads of motors as permitted in Section 430-145(b)
2. In lengths not in excess of 6 ft (1.83 m)
a. For utilizing equipment, or
b. As part of a listed assembly, or
c. For tap connections to lighting fixtures as permitted in Section 410-67(c)
3. For manufactured wiring systems as permitted in Section 604-6(a)
4. In hoistways, as permitted in Section 620-21(a)(1)
5. As part of a listed assembly to connect wired fixture sections as permitted in Section 410-77(c)
 
  #6  
Old 05-25-01, 02:10 PM
Wgoodrich
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YOU SAID;
> Does the short run limitation you mentioned previously also apply to metal clad, AC cable and greenfield?
REPLY;
The 6' limitation only applies to any flex that is 3/8" in diameter. 1/2" is the normal minimum size of flexible metallic conduit [aka; flex,greenfield, etc.] Metal clad and type AC is a permanufactured product not approved to have wires fished into them in the field.
YOU SAID;
> If so, what are your thoughts on these products compare to Romex in terms of safety? Again, I can't imagine armored cable isn't at least as safe as romex - so why a length limitation on it but not Romex? Am I missing an important issue/consideration?
REPLY;
You missed the intent of the 6' limitation to being any flexible metal conduit smaller than 1/2" in diameter.

As for Romex being more safe than flexible metal etc, Romex is decreasing in its limitations of applications. Considering a 25 plus year track record showing its ability to be safe while in great demand and use world wide, of nonmetallic sheathed cable [aka' Romex], we now find Romex to be used almost anywhere flexible metal conduits are used. The only place that Romex is limited where flexible metal conduit is allowed to my knowledge is now places of assembly or more than three stories high structures.
YOU SAID;
> Does greenfield have a typical outside diameter that will help me identify it (or is that the greater than 3/8" that you mentioned previously)? OR, do I just look to see if the armored cable has standard t/w wire without the paper wrap, etc.?
REPLY;
Never fish new wire inside any flexible metallic conduit that is smaller than 1/2" in diameter, whether existing or new.
YOU SAID;
> Assuning I find greenfield in my house - and want to replace the older wire - will fishtape pull through greenfield without snagging or is it more trouble than it's worth?
REPLY;
I really doubt you will find any home substantially wired in 1/2" flexible metal conduit or larger, but if you did then you should have little trouble fishing new wire in it and it should be approved. AGAIN, NEVER FISH NEW WIRE IN A 3/8" FLEXIBLE METAL CONDUIT THAT IS LONGER THAN 6' IN LENGTH.
YOU SAID;
Thanks for taking the time to educate me - I really appreciate getting feedback from a knowledgable professional.
REPLY;

Glad if I was able to be of some help.

Now a little insert of opinion and experience. I have been an electrician for over 30 years, and an electrical educator, and public official most of that time along with owning and operating an electrical company of approximately 10 to 15 employees, and being a 20 year landlord owning operating 22 apartment units.

I have never seen anywhere that any incident of shock or fire occurred and Romex had been installed within the minimum safety standards as required, when I could say "See, if that were in conduit that would not have happened."

I have seen misuse and improper installations causing either shock or fire while both metal, PVC, flex, etc. conduit was used and where nonmetallic sheathed cable aka Romex was used.

I see neither wiring style to be safer than each other. There are times when heavy wall rigid style conduit needs to be used due to subject to physical damage was present.

The NEC even allows Romex to be installed and sleaved in conduit where those locations of exposed to physical damage existed. Type NMC is even allowed to be direct buried. Type NMS is now showing in the market to approach approved use in the places of assemblies such as theaters and churches etc.

Quite proud of the track record, reduced cost, ease of installation, degree of safety concerning nonmetallic sheathed cable aka Romex.

Beleive you will find more uses appear approved as time goes by.

Hope this helps

Wg
 
  #7  
Old 05-25-01, 05:07 PM
Guest
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wg;
whew!
i'm getting dizzy!
 
  #8  
Old 05-26-01, 09:15 AM
edbreyer
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Smile wGoodrich...

Once more - Thanks for all the information. I am going to copy your responses for ongoing reference.

Now I know I'm going to seem a little dense - but I just want to make sure I've got it:

> The 6ft length limitation only applies to smaller than 1/2" diameter FLEX that is hollow from the factory (where the installer feeds the wires). This limitation is due to concern that wires can be damaged when attempting to fish them through longer lengths of small diameter FLEX.

> The length limitation does NOT apply to Armored Cable prewired from the factory because - since the wire is already inside - the issue of damaging the wires when fishing them through is a mute point.

That's the impression I got but I wanted to be sure. What it really comes down to is whether I'm violating any saftey codes when I install a 25 to 50 foot run of 14/2 or 12/2 AC cable.

NOW FOR SOME OTHER QUESTIONS (IF YOU HAVE THE TIME):

BACKGROUND:
I have done extensive electrical work in my previous homes - including installing a new electrical panel (to change from fuses to circuit breakers - not AMP upgrade). In this instance however, I'm fairly certain that I will need to pull larger wires from the meter to the new panel (current wires for 60 amp service don't appear to be 3 gauge).

> If I install a new 100 AMP circuit panel - is 3 gauge wire sufficient for the aprox. 5foot run from the meter to the panel?

> What size piping is required for the 3 gauge (or whatever size you reccomend) wires.

> Do electricians generally install a new meter box and mast pole/head when upgrading from 60 to 100 AMP panels - or do the utilities generally do this?

By the way - our town does allow us homeowners to do this work ourselves as long as we pass inspection (based on 96 NEC). Funny isn't it - this is the same area that doesn't allow romex : ^ ) - And yes I am very familiar with pulling meters and working in/on service panels.

Thanks for your time!

Ed
 
  #9  
Old 05-26-01, 03:30 PM
Wgoodrich
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I think you got the drift concerning flex, greenfield, metal clad manufactered in factory and type AC also manufactured in factory. Remember if you mess with the design of a manufactured product you would be in violation of 110-3 of the NEC requiring the product be used as listed and / or labeled. Both metal clad and type AC cable is allowed to be used just about the same as romex except metal clad is allowed in places of assembly and Romex is yet to be approved for places of assembly.

Now for your new questions;

> If I install a new 100 AMP circuit panel - is 3 gauge wire sufficient for the aprox. 5foot run from the meter to the panel?
By the NEC 310-15-B-6 allows 100 amp residential services to be wired with #4 copper which is one size smaller than your # 3, so your size would be ok for use with 100 amp residential services.
> What size piping is required for the 3 gauge (or whatever size you reccomend) wires.
Sch 80 PVC for 3 #3 THHW OR THW conductors would be 1 1/4"
Rigid Metal conduit for 3 #3 THHW OR THW conductors would be 1".
> Do electricians generally install a new meter box and mast pole/head when upgrading from 60 to 100 AMP panels - or do the utilities generally do this?
Electricians usually install the entire service equipment. Sometimes the owner supplies the meterbase and sometimes the utility company supplies the meterbase. However customer or electrician usually supplies it. BE aware that the entire service must be usgraded to be compatible with the larger service that is usually including but not limited to everything from the point of attachement of the utility company to the panel and grounding source.

By the way - our town does allow us homeowners to do this work ourselves as long as we pass inspection (based on 96 NEC). Funny isn't it - this is the same area that doesn't allow romex : ^ ) - And yes I am very familiar with pulling meters and working in/on service panels.

Check with your local inspector and utility company. In our area you could have charges filed against you if you removed or tampered with a meter. The utility company removes the meter and power from the structure, the inspector then approves the new installation then the utility company makes the new connections and reinstalls the meter for you.

PS; I still think you guys are paying the price for the poor old cow that just made one little bitty mistake of kicking the bucket. Just because Chicago just about burnt to the ground doesn't mean they still have to pick on poor old betsy the cow. Just funnin.

Hope this helps

Wg
 
  #10  
Old 05-27-01, 10:28 PM
edbreyer
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Thumbs up Thanks Wgoodrich!

Once again you've provided excellent info - I greatly appreciate it! I may have some more questions for you in the weeks ahead once I start the electrical work in my new (to me) house.

ED
 
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