Sub Panel question on conduit

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  #1  
Old 08-16-15, 06:46 AM
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Sub Panel question on conduit

I am going to add a sub panel to my 200 amp service panel as I ran out of room to install a whole house surge protector. I will need to move a few circuits over to the sub panel. I bought a 125 amp sub panel and stuck it next to the main panel thinking I was going to use a 4 conductor cable but changed my mind on breaker size etc and am going to make it larger. I know not to bond the nuetral and added a new separate ground bar in the sub panel. That brings up my question. If I use a piece of EMT or pipe to connect the main and sub together, I am pretty much "bonding" the boxes and that is wrong. So I bought some 1 1/4 electrical PVC pipe and the proper fittings to solve that. But what about the EMT on the circuits I need to move over to the sub panel? They are bonded to the main box as it is a steel building work shop and the EMT and steel boxes are screwed into the steel building. Do I need to replace all the EMT and only use plastic conduit from the sub panel?? Or is is fine to just use an non-metallic adapter at the sub panel to connect my EMT to to break the metal connection to the bonded steel building frame?
Thanks,
G
 

Last edited by Grumple; 08-16-15 at 07:17 AM.
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  #2  
Old 08-16-15, 07:15 AM
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You can use metallic conduit between the two panels. You do not use the bond screw to bond the neutral to the enclosure in the subpanel.
 
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Old 08-16-15, 07:16 AM
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If I use a piece of EMT or pipe to connect the main and sub together, I am pretty much "bonding" the boxes and that is wrong.
No, the boxes are bonded. It is usually done with metal conduit except a threaded nipple is usually used if they are close together.
So I bought some 1 1/4 electrical PVC pipe and the proper fittings to solve that.
No problem to solve but one to create. You now need a ground wire. With a steel nipple the ground wire is optional.
Do I need to replace all the EMT and only use plastic conduit from the sub panel??
No. Just use metal conduit for every thing.
I was going to use a 4 conductor cable
No, use THHN/THWN individual wires. You can probably use one 2" nipple for everything.
 
  #4  
Old 08-16-15, 07:22 AM
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The reason I asked is because I figured an metallic connection between the two panels was about the same as bonding them. And then I read this:

distance rule with sub-panels? - The Inspector's Journal Forums

So it made me think that I could still be bonding through the building frame. Maybe I am getting grounding and bonding confused but it seemed like a good question.
Thanks,
G
 
  #5  
Old 08-16-15, 07:27 AM
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ray,
I am already planning to use a ground wire. I have 3- 2 awg THHN wires for the mains and neutral and a #6 green for the ground bar. And a 100 amp breaker from the main to the sub. So I guess I was worried a little because of the post I linked to below. Sounds good to me. Looks like I was over thinking the bonding that's all.
Thanks,
G
 
  #6  
Old 08-17-15, 07:19 AM
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All exposed metal (panels, junction boxes, etc) through the whole electrical system are supposed to be bonded together and to ground. The neutral gets bonded to ground only in the main panel. Everywhere else in the electrical system the neutral must be kept separate from the grounded metal boxes.

It is very common when mounting two panels side by side to use a 2-3" pipe nipple, 4 lock nuts and two bushings to make a solid metal pathway between the panels.
 
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Old 08-17-15, 07:24 AM
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I was going to use a 4 conductor cable
Is this 3-phase or did you mean 3-conductor cable, white, black, red + ground?
 
  #8  
Old 08-17-15, 08:28 AM
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Yes, it is all clear now. It's my first sub panel install so I figured I would be safe by asking a possibly dumb question. That is exactly what I was thinking, but the non-bonded neutral needed some further explanation. The "everywhere else in the electrical system the neutral must be kept separate from the grounded metal boxes" part I knew not to bond the sub panel, but didn't completely understand why. I know it has to do with safety and a potential shock hazard under a certain circumstance, but never had to deal with it before. That is why I asked, especially when I read that story on the page I linked.
I just finished the mounting of the box a few minutes ago. I used a 2" (probably could have went smaller) galvanized nipple 4 inches long and 4 lock nuts and 2 bushings. I bought all the parts yesterday. I was a bit confused by the varying knockout sizes as it appears it goes from 1- 1/4" to 2" but there was one for 1- 3/4" but there are no electrical lock nuts or bushings to match. I built and wired my whole 2400 square foot workshop years ago but this is my first sub panel.
Thanks,
G
 
  #9  
Old 08-17-15, 08:32 AM
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ray,
This is single phase 200 amp service. I did in fact mean 3 conductor w/ground. I have everything but the 2 awg in white as the local big box stores do not carry it. I know I can use tape but I like to do my stuff with the correct colors. I will have to mail order a piece or make a few phone calls and see if I can drive and get a piece. Otherwise I will just order it from Home Depot and have it shipped. I think I could use a 4 awg for the neutral but will probably just go with the #2.
Thanks,
G
 
  #10  
Old 08-17-15, 11:06 AM
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Above a certain size they don't make any colors other than black unless you're ordering somewhere in the 5000'+ range. White taping is industry standard practice on panel feeders. If you really want to go all out you could get some white shrink tube.
 
  #11  
Old 08-17-15, 12:23 PM
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I realize that (about the tape) but you can still get a short piece online or ebay. I thought about the white heat shrink but already ordered some #2 white from HD and it will ship to the store for free. I will pick it up when it arrives as I am in no big hurry. The main reason I had to add a sub panel is so I could make room for a whole house surge protector as we had some bad luck with lightning recently that took out some $$ electronics. And it happened 3 times in less than 2 months! And I have no less than 10 APC Battery BackUps connected to the equipment that was damaged. Florida...the lightning capital of the USA.
 
  #12  
Old 08-17-15, 12:42 PM
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Make sure that the grounding electrodes (earth grounding) of your electrical service is at or above modern code standards to get the best out of your surge protectors. Follow single point grounding principles for your telecom and other utilities entrance to the building.

The minimum you would want is grounding to the water service entrance pipe plus a ground rod bonded with #4 copper wire. You should have an intersystem grounding bridge where your phone, CATV, satellite services all ground to. The gas or propane lines should also be bonded if you have them.

We aren't too far behind you in terms of lightning strikes with storms coming in off the lakes.
 
  #13  
Old 08-17-15, 01:48 PM
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Well, the first thing I did after the first or second strike nearby was to inspect my ground rod. I simply removed it (it was a galvanized rod) and replaced it with 3 copper rods connected with a single #4 bare copper and spaced them 16 feet apart in a line. I was going to put in a delta but my septic system was in the way. All of my utility (cable and phone) are tied in to the #4 bare at the service entrance. I also added coax surge protection and an Eaton whole house surge protector. No gas or propane here. We have PVC water pipe hook ups here.
I figured I would add another whole house surge unit to the workshop as I have DRO's and welders and a pc down there and would hate to see them taken out. Incidentally, I have underground CAT5E for internet connection to the workshop and it too is protected at both ends with APC brand surge devices with a single point ground to avoid a ground loop between buildings.
 
  #14  
Old 08-18-15, 06:50 AM
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It is this simple. How many feet from each incoming wire to the earth ground rods. Best surge protection for a neutral wire is a direct connection connected low impedance (ie less than 10 feet) to earth. But a neutral wire in a sub-panel (and all other incoming wires) cannot connect directly. So a 'whole house' protector does what that direct connection does better.

A protector is only as effective as its earth ground and connection. Every additional foot of wire between that protector (including the APC one for ethernet) and earth ground diminishes protection.

And yes, the neutral wire in a subpanel must connect that short to earth via a protector - because the neutral wire cannot connect directly.
 
  #15  
Old 08-18-15, 08:47 AM
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westom,
Yeah, I understand how the surge protection devices work. They want them connected to the top of the bus (if possible) through a 50 amp dual pole breaker. And 1 foot or less on the lead lengths. I bought the Eaton CHSP2ULTRA's as they cover 4 lines as opposed to the cheaper ones that only cover 2. Basically a box full of MOV's and are sacrificial when they do the job either once really good, or a lot of times with little surges.

As far as the single point ground on the RJ45 surge protectors, it is about 180 feet between buildings. APC instructed me on what to do and I have a ground wire in a conduit along with the CAT5E wiring that puts both protectors on the same ground.
Thanks,
G

p.s. I found some good reading on sub panel bonding and why you do not do it here in case anyone is interested.

http://www.mikeholt.com/forum/Forum1/HTML/003455.html
 
  #16  
Old 08-18-15, 02:06 PM
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Knowledge of how a protector works means MOVs are never sacrificial devices. MOVs fail only because the protector is grossly undersized, no properly earthed, and other reasons. Your protector should be confronted by multiple direct lightning strikes and remain function. Protectors with very little protection and obscene profit margins fail. That increases sales.

The ground wire on an APC Ethernet connector must connect low impedance (ie less than 10 feet) to earth ground. Not to any safety ground or conduit. That is not earth ground. Also critically important - that ground wire must never be inside metallic conduit. Conduit further increases impedance - diminishes protection.

An APC Ethernet protector must be at both ends of the Ethernet wire. And each protector must connect to the single point earth ground for that end. All four words in that expression have engineering significance. The only earth ground that matters for each building is the one at that building. A ground wire interconnecting the two single point grounds can increase protection IF the ground wire is outside the conduit and best in contact with earth. Ground wire inside conduit does much for makes a common 60 Hz human safety ground and little to nothing for making a surge protection ground.
 
  #17  
Old 08-18-15, 09:14 PM
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Well I know MOV's seem to be able to withstand many hits but eventually they need replacement. I guess I have seen a pic or two when the MOV's took a humongous hit and sacrificed themselves and also protected the property. If you look up the Eaton unit I bought from Home Depot there is a customer pic of such an event.

The ground wire for the APC surge protectors for the RJ45 wiring that I have set up is in a buried pvc pipe and is not a bare wire. I questioned the guys at APC and they said to connect it the way I have it although I thought it would be better to connect each unit (I have one on both ends) with the ground at each building. They were worried about a ground loop. So you are saying what I was thinking then that the surge protectors on each end of the 180 foot run should be grounded separately at each location preferably to the bare ground that connects to the ground rod?
Thanks,
G
 
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Old 08-19-15, 01:27 PM
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I guess I have seen a pic or two when the MOV's took a humongous hit and sacrificed themselves and also protected the property.
If a surge is too large for an MOV, MOV must disconnect from that surge. And leave that surge still connected to appliances. This failure due to a protector being grossly undersized. That 'failed' indicator light can only report when the protector was grossly undersized. It cannot report the acceptable failure mode: degradation.

Sometimes that thermal fuse does not disconnect fast enough. Then catastrophic failure (sometimes a fire) results. Again, any properly sized protect must only degrade and never fail catastrophically (sacrifice itself).

How many surges can a properly sized MOV take before it only degrades - does not fail catastrophically - Vb changes by 10%? A test is defined by one MOV manufacturer:
The change of Vb shall be measured after the impulse listed below is applied 10,000 times continuously with the interval of ten seconds at room temperature.
MOVs must only degrade - not fail catastrophically or "sacrifice".
 
  #19  
Old 08-21-15, 08:09 AM
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I see what you are saying and it makes perfect sense now that I think about it. I guess a properly constructed surge protector is the key here. I remember in the old days where people would just attach a MOV across the leads of an outlet on the back side for a cheap, and potentially dangerous, form of surge protection. No fuse protection there. Good info. I found this to further make me smarter on MOV sizing etc. I guess I didn't know how complicated the math could get on sizing a MOV.

Select the Right Varistors for Overvoltage Circuit Protection | Power content from Electronic Design

Thanks,
G
 
  #20  
Old 08-21-15, 09:34 AM
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Article about MOVs only discusses that one part of a system. It is technically flawed in that degradation should never cause a thermal fuse to blow. A thermal fuse only blows (trips) when the MOV is grossly undersized - to avert a catastrophic failure - a fire.

You remembered MOVs between two AC wires. That is for a type of surge already made irrelevant by what is standard inside all appliances (electronics and motorized). Most think an MOV between any two AC wires means a surge current incoming on one wire and that same current outgoing on another. Destructive surges do not operate that way.

A destructive surge means a current is incoming (in the same direction) on any or all AC wires. For example, let's assume a current only on a black wire creates 5000 volts. An MOV (maybe 350 volts) means 5000 volts on the black wire and 4650 volts on white and green wires. Again, that current is flowing in the same direction on all wires. That power strip protector has now connected 5000 volts incoming to a computer on one wire. And 4650 volts on other two AC wires.

That 4650 volts now on a green safety ground wire connected directly to a computer's motherboard - bypassing protection in a PSU. So that power strip protector makes damage easier. We saw repeatedly by even replacing every damaged semiconductor in that surge current's path to submit reports to a design review. So avert future damage.

Only way to avert that damage is to connect that surge to earth at the service entrance. IOW a power strip protector in a building without a properly earthed 'whole house' protector can even make surge damage easier. That article does not discuss how a surge gets from cloud (or AC mains) to earth. Effective surge protection must always discuss the entire system from cloud to distant earth borne charges.

A protector is only as effective as its earth ground. MOV sizing is about MOV life expectancy over many surges. Earthing and that connection defines protector during each surge. A protector is only as effective as its earth ground. Damage is all about a completely different type of surge. Most who recommend protectors do not even understand that other and different type of surge current.
 
  #21  
Old 08-22-15, 07:28 AM
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Good info. Thanks for the explanation. I have 3 ground rods so I think i have that part covered. I hope my Eaton unit does some good as that is what I installed on the house and workshop. Do you think the Eaton is any good? :

Eaton Whole House Surge Protector-CHSPT2ULTRA - The Home Depot

Do you work here? :

Zero Surge | Superior, non-MOV surge protectors

What do you think of their products? I have been here over 25 years and never really had any lightning problems to speak of. Maybe one TV, and a modem get damaged. But this year was just close strikes and bad luck. I am also thinking the particular product I switched to for my 10/100 to Gigabit network may have had something to do with the problems. I also may have discovered a bad APC so who knows...

I also found a place a few weeks ago that was overseas and they were advertising surge protection that "stopped the surge, not divert the surge" but I can't seem to find the link but will post it here when I do. They showed some pretty good live tests that appeared to work. They also did not list any prices. Probably a high capacity capacitor in a box.
Thanks,
G
 
  #22  
Old 08-22-15, 01:10 PM
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A nearby strike that does not connect inside the house is mostly irrelevant. A strike far down the street to utility wires is a direct strike incoming to every household appliance.

Lightning is typically 20,000 amps. So a minimal 'whole house' protector should be 50,000 amps. Apparently, in your venue, that is sufficient. Some venues need 100,000 amp protectors. That is about protector life expectancy over many strikes.

Zero surge is a series mode filter. Its spec numbers claim something maybe equivalent to a 600 joule protector. IOW most of hundreds of thousands of joules pass right through it. But it does not fail. Somehow that gets the many, educated by advertising, to recommend it.

Anything that would somehow block a surge is only for surges already made irrelevant by what should be inside all appliances.

A protector is only as effective as its earth ground. If a hardwire from breaker box to earth goes up over the foundation and down to multiple earth ground rods, then protection has been compromised. Relevant expression is low impedance. That hardwire has multiple sharp bends over the foundation. It is bundled with other non-grounding wires. It should go through the foundation to earth ground rods to remove many feet of wire. Also, if inside metallic conduit, then it is all but not connected to earth.

Most critical discussion of protection focuses on what does that protection - earth ground and how that connection is made. That may also explain why the 10/100 Megabit(?) network got damaged.

Anything that might 'stop a surge' is only trying to do what is already inside all appliances. For example, ethernet ports already stop surges up to 2000 volts. But if a surge cannot find a better path to earth, then a surge increases its voltage to blow through that ethernet port. This does not happen if a surge current connects to earth BEFORE entering the building. Any damage means a surge was all but inviting to go hunting inside.
 
  #23  
Old 08-23-15, 10:09 AM
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A nearby strike that does not connect inside the house is mostly irrelevant. A strike far down the street to utility wires is a direct strike incoming to every household appliance.
So I guess that strike must have hit the power line but hard to prove.

Lightning is typically 20,000 amps. So a minimal 'whole house' protector should be 50,000 amps. Apparently, in your venue, that is sufficient. Some venues need 100,000 amp protectors. That is about protector life expectancy over many strikes.
So my device is definitely better than nothing and a good first layer and hopefully enough to keep the gremlins out of the house.

Zero surge is a series mode filter. Its spec numbers claim something maybe equivalent to a 600 joule protector. IOW most of hundreds of thousands of joules pass right through it. But it does not fail. Somehow that gets the many, educated by advertising, to recommend it.
Anything that would somehow block a surge is only for surges already made irrelevant by what should be inside all appliances.
Glad you explained that as it makes perfect sense somebody could assume if their device never breaks, it works better than the other devices that actually work.



A protector is only as effective as its earth ground. If a hardwire from breaker box to earth goes up over the foundation and down to multiple earth ground rods, then protection has been compromised. Relevant expression is low impedance. That hardwire has multiple sharp bends over the foundation. It is bundled with other non-grounding wires. It should go through the foundation to earth ground rods to remove many feet of wire. Also, if inside metallic conduit, then it is all but not connected to earth.
Most critical discussion of protection focuses on what does that protection - earth ground and how that connection is made.
Well I hope my ground system is good as I knew to space multiple ground rods "at least" 8 feet apart (or the length of the rod apart) so I went with 16 feet. I did not use exothermic welds but used 2 clamps on each with a single bare copper wire and no sharp bends and other than where the copper wire is attached to the wall, it is not touching the foundation. And no conduit.

That may also explain why the 10/100 Megabit(?) network got damaged.
I keep thinking I have a bad APC based on what I found when adding another new one into my room. I have an older model that "appears" to work normally but when I tried to isolate my router and modem wall warts by connecting it to this unit alone, I noticed something odd. When I connected a surge arrest to the battery backup port and then plug the wall warts into it, I turned on the surge strip switch and the APC kicked on for a second as if it sensed a surge. I thought that seemed weird so I swapped out the APC with another same exact model and tried the same test and this APC didn't react the same. It just stayed quiet and normal like it should. I figured a modem and router wall wart is not that big of a load so maybe I found the weak link.


Anything that might 'stop a surge' is only trying to do what is already inside all appliances. For example, ethernet ports already stop surges up to 2000 volts. But if a surge cannot find a better path to earth, then a surge increases its voltage to blow through that ethernet port. This does not happen if a surge current connects to earth BEFORE entering the building. Any damage means a surge was all but inviting to go hunting inside.
Very well said. Most devices have some form of self protection whether it is designed into it like MOV's, inductors, transformers, in power supplies or even fuses.

Last question...How does a "wall wart" on above said modem and router get away with no ground wire?? They use 2 prong plugs. I am sure the neutral plays a part, or the design of the power supply. But I think (I may be wrong) that the power supply connected to a bad APC could have taken the surge and internally took a hit that then shorted and sent the surge into the modem or router and overwhelmed it and the damage kept heading upstream through the CAT5E Ethernet port and the rest is history. Could a poorly designed wall wart power supply fail in such a way?

Thanks,
G
 
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Old 08-24-15, 08:07 AM
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Wall receptacle safety ground is not earth ground. That third prong is for human protection; not ror transistor protection. Since a wall wart includes galvanic isolation, double insulated, etc, then it does not need a safety ground connection to an AC receptacle.

If a surge is not earthed at the service entrance, then it hunts for earth destructively via any and all AC wires - including the two prongs on that wall wart. This destructive surge increases voltage as necessary to blow through a wall wart's galvanic isolation (and other protection). Sometimes that third prong (on any electronics) even provides a surge with a easier path destructively through that appliance.

Wall warts (like other electronics supplies) will typically block voltages in excess of 600 volts - often up to 1000 volts. That is what a surge can create IF not first connected to earth BEFORE entering a building.

Do not confuse safety ground in receptacles with earth ground. They are interconnected and electrically different.
 
  #25  
Old 08-24-15, 08:18 AM
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Ok, thanks for the explanation yet again. I guess I am just trying to make sure I have done everything I can to prevent what the recent 3 damaging surges from lightning cost me. APC devices check for ground fault when installing them so it seems they use it for something. Maybe that is why I get a little confused. But I completely understand to use a whole house protector to keep the surge out as the first line in a tiered approach to overall protection.
Thanks,
G

p.s. I guess I am mainly trying to figure out if one of my imported routers or switches was the main reason I got hosed as the router and switches were the things taken out and what was connected to them got taken out too. Just trying to put my finger on it.
 
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Old 08-24-15, 08:31 AM
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APC devices do not check for earth ground. It can only report when a safety ground is detected. It cannot even say safety ground is good. It can only report some types of safety ground defects. And says nothing about earth ground.

Every protection layer is only defined by an earth ground. APC has no earth ground - cannot be a layer of protection. 'Whole house' protector is a 'secondary' protection layer - not the first line of defense. A picture demonstrates what in your 'primary' protection layer should be inspected:
Florida Power & Light and BellSouth

Each protection layer is only defined by an earth ground. No plug-in protector has or will discuss what is necessary to protect from destructive types of surges.

What may explain recent damage? Improper grounding (is a new wire connected to earth by touching a water pipe, etc means another path to earth that is not via the single point earth ground.
 
  #27  
Old 08-24-15, 11:18 AM
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Wow! This is the best info yet. I was seriously going to call the power company as they recently were in the area and connected some wires to a utility pole that was added for the interstate spy cameras and Amber Alerts etc. The crew first bored or drilled a hole and set in a concrete pole and 1 extra long (20 foot I think) ground rod. I noticed they had hit water and were having trouble and I even asked why such a long ground rod based on the high water table around here. They said all government work requires it no matter what. I heard them say they would have to pull the concrete pole out and attach some kind of plate due to it sinking in the hole. Anyhow, I did not watch that part. A month or so later they removed the pole and ended up putting it down on the end of the road for some reason. I guess it was because they put it too close to the other power pole as it was within 10 or 20 foot of it. I think I will call today and have someone check their handy work.
Thanks again,
G

added: I called and they are going to look at the lightning circuit breaker and when I mentioned the ground wire he said that really doesn't matter because it happens so fast the lightning will go down the pole.
 

Last edited by Grumple; 08-24-15 at 12:16 PM.
  #28  
Old 08-25-15, 09:18 PM
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Hi Grumple, You wrote: "The reason I asked is because I figured an metallic connection between the two panels was about the same as bonding them." I wonder how and why you figured that metallic connection between two panels was about the same as bonding them??? With all respect that figuration is non sense. Remember that the Neutral is NOT bonded to Ground by default, that's why you have Neutral connected to a Neutral bus bar, etc. that is "floating" isolated in a plastic base NOT touching any metal on the panel, therefore it DOESN'T matter how much metallic conduit you use from Main Panel to a Subpanel that will never mean bonding the Neutral to Ground because you are suppose to have the Neutral NOT touching any metal enclose or conduit at all in the subpanel. The effect that the metallic conduit provides is a Ground connection and serves only for Grounding purposes not to bond the Neutral, so under normal circumstances using metallic or not conduit with only have effect on how you will provide your Grounding NOT your Neutral... However, of course you can affect the Neutral by ON PURPOSE BONDING IT TO YOUR GROUNDING if you need to in a Main Panel, in this scenario the bonding screw does not add the grounding to the neutral but add the neutral to the grounding by eliminating its "floating isolation" on the panel connecting it to the Metal Enclosure of the panel, but notice that the Neutral bonding to the Grounding is achieve at the Metal Enclosure of the Panel, not at the Metallic Conduit, therefore you can still bond the Neutral to the Grounding regardless if you use or not a metallic conduit due that you are required to have a Grounding Wire going from your Main Panel to your Subpanel too, and also your Main Panel is suppose to be properly grounded. So all this means that if you believed that using a Metallic Conduit going from your Main Panel to Subpanel was going to bond your Neutral to your Grounding, then you should fear that the same will happen with your Grounding Wire going from one panel to the subpanel too... but you should know that because a grounding wire is required then it will not bond the Neutral to Grounding in either cases, because otherwise the NOT BONDING AT THE SUBPANEL CODE could never be met. Therefore, you should figure that your figuration was extremely non sense. Unless of course you were wondering about using or not the bonding screw at the subpanel which is a more legit doubt than believing a metallic conduit will have the same effect.

In conclusion I think what you stated explaining why you asked your first question of your post, was an excuse to your ignorance.

Thank you.
 

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  #29  
Old 08-26-15, 04:36 AM
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Definitions: Bonded (Bonding) Connected to establish electrical continuity and conductivity.

Stating something is bonded does not mean that the ground and neutral are connected together, it only means they are connected together. SO the OP's original statement:

If I use a piece of EMT or (steel) pipe to connect the main and sub together, I am pretty much "bonding" the boxes
Is 100% correct if the run is continuous, and the proper fittings are used.
 
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Old 08-26-15, 06:31 AM
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JosiQDIY2015
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Hi Grumple, You wrote: "The reason I asked is because I figured an metallic connection between the two panels was about the same as bonding them." I wonder how and why you figured that metallic connection between two panels was about the same as bonding them??? With all respect that figuration is non sense. Remember that the Neutral is NOT bonded to Ground by default, that's why you have Neutral connected to a Neutral bus bar, etc. that is "floating" isolated in a plastic base NOT touching any metal on the panel, therefore it DOESN'T matter how much metallic conduit you use from Main Panel to a Subpanel that will never mean bonding the Neutral to Ground because you are suppose to have the Neutral NOT touching any metal enclose or conduit at all in the subpanel. The effect that the metallic conduit provides is a Ground connection and serves only for Grounding purposes not to bond the Neutral, so under normal circumstances using metallic or not conduit with only have effect on how you will provide your Grounding NOT your Neutral... However, of course you can affect the Neutral by ON PURPOSE BONDING IT TO YOUR GROUNDING if you need to in a Main Panel, in this scenario the bonding screw does not add the grounding to the neutral but add the neutral to the grounding by eliminating its "floating isolation" on the panel connecting it to the Metal Enclosure of the panel, but notice that the Neutral bonding to the Grounding is achieve at the Metal Enclosure of the Panel, not at the Metallic Conduit, therefore you can still bond the Neutral to the Grounding regardless if you use or not a metallic conduit due that you are required to have a Grounding Wire going from your Main Panel to your Subpanel too, and also your Main Panel is suppose to be properly grounded. So all this means that if you believed that using a Metallic Conduit going from your Main Panel to Subpanel was going to bond your Neutral to your Grounding, then you should fear that the same will happen with your Grounding Wire going from one panel to the subpanel too... but you should know that because a grounding wire is required then it will not bond the Neutral to Grounding in either cases, because otherwise the NOT BONDING AT THE SUBPANEL CODE could never be met. Therefore, you should figure that your figuration was extremely non sense. Unless of course you were wondering about using or not the bonding screw at the subpanel which is a more legit doubt than believing a metallic conduit will have the same effect.

In conclusion I think what you stated explaining why you asked your first question of your post, was an excuse to your ignorance.

Thank you.
Well thank you for your most friendly response to my question. I did mention it was my first sub panel so I wanted to be sure what I was doing? I guess that makes me ignorant. I was just over thinking that the main panel has the neutral bonded to the main service panel, thereby the bond between the boxes *almost* meant the same thing. Then I read that most confusing article I linked to in one of my replies. I thought asking a question was what this forum was for and if I was 100% sure I would not have asked in the first place. Sure better to ask and understand if even the slightest bit confused (ignorant), then to do something unsafe.
Thank you,
G

p.s. Of course I understand it now, just had a senior moment due to 3 lightning strikes in 5 weeks and sorting through the damage and trying to prevent more in the future. And YES, the plastic isolator on the neutral bars was the part I missed.

p.s.s. Article that messed my head up:
distance rule with sub-panels? - The Inspector's Journal Forums

In conclusion I am a complete eediot and can never do anything right!
 

Last edited by Grumple; 08-26-15 at 06:55 AM.
  #31  
Old 08-26-15, 06:39 AM
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Definitions: Bonded (Bonding) Connected to establish electrical continuity and conductivity.

Stating something is bonded does not mean that the ground and neutral are connected together, it only means they are connected together. SO the OP's original statement:

If I use a piece of EMT or (steel) pipe to connect the main and sub together, I am pretty much "bonding" the boxes
Is 100% correct if the run is continuous, and the proper fittings are used.
I got it. Like I said earlier, I just had a senior moment mainly after reading that article I linked to as I did not understand what they were referring to as the image was not clear and there was also a lot of other people confused. And it was an "inspector" forum.
Thanks,
G
 
  #32  
Old 08-26-15, 07:05 AM
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That forum is for home inspectors, not electrical inspectors. Home inspectors are typically generalists and do not have a background in the codes and practices. They can write up things that are already code compliant. A common issue is a switch next to a shower. The electrical code says it just has to be outside the footprint. They will write it as a defect since they think you can touch it while in the shower and get shocked.
 
  #33  
Old 08-26-15, 08:54 AM
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However, of course you can affect the Neutral by ON PURPOSE BONDING IT TO YOUR GROUNDING if you need to in a Main Panel, in this scenario the bonding screw does not add the grounding to the neutral but add the neutral to the grounding by eliminating its "floating isolation" on the panel connecting it to the Metal Enclosure of the panel
This also sounds like misleading and incorrect home inspector language. In the main panel, the neutral must be directly grounded by the GEC and not simply bonded to ground through a bonding screw or strap. This is accomplished by terminating the GEC on the neutral bus. The purpose of the bonding screw or strap is to bond the enclosure to ground.
 
  #34  
Old 08-26-15, 09:13 AM
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If the ground is not bonded to the neutral the breaker will not trip. A ground rod has no function in the normal operation of a circuit. The resistance of the earth is too high to trip a breaker.
 
  #35  
Old 08-26-15, 05:35 PM
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Hi CasualJoe,

In my explanation I was referring regarding the bonding screw to bond the Neutral to the Enclosure in the Main Panel or Subpanel ONLY, but of course that a Grounding Electrode to Earth terminating in the Ground bus bar is ALWAYS NEEDED IN THE MAIN PANEL and even in the Subpanel if is installed in a detached building; but that is so extremely basic that is not even needed to be mention in most of the cases; also OP's House MUST have a GEC correctly installed in the Main Panel already.

The way I wrote that sentence could be a little difficult to understand but it was clear that I was referring to the Bonding Screw only because in the sentence you quoted above, I ended it mentioning that the bonding connection I was referring is adding the Neutral to the metal enclosure of the panel specifically; and remember that the OP's confusion was in the context of if a metallic conduit will have the same effect of a bonding screw in the Subpanel, and not about a GEC in any way.


Thank you.
 
  #36  
Old 08-26-15, 05:49 PM
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Hi Tolyn Ironhand,

You are right in the specific context of your statement... but OP's confusion was not in that same context. He was believing that bonding both boxes could equal bonding the Subpanel Neutral to the Ground enclosure like when you use the bonding screw to bond it in the Main Panel. Problem was that OP original context was misleading and you were unable to interpret his actual confusion but I was able to do it.

And the proof of this is that after my criticisms the OP made a reply to me where at the end he stated this: ''And YES, the plastic isolator on the neutral bars was the part I missed.'' As you can see he accepted that he missed to notice the plastic isolator that keeps the Neutral separated from the Grounding (unless you use the bonding screw of course); therefore, this confirms that he was believing that bonding the two boxes via metallic conduit will equal that the Neutral bus bar in the Subpanel was going to be directly bonded to the main panel ground enclosure via the metallic conduit too; but again that is obviously not correct unless you use the bonding screw to bond the Neutral to the Ground in the enclosure but this can be performed or not regardless if you use a metallic conduit to GROUNDING BOND both boxes enclosures or not.

Thank you.

Jos
 
  #37  
Old 08-26-15, 06:56 PM
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of course that a Grounding Electrode to Earth terminating in the Ground bus bar is ALWAYS NEEDED IN THE MAIN PANEL
In the main panel, the GEC must terminate on the neutral bus. If the GEC terminates on the ground bar there must be an appropriately sized jumper between the ground bar and the neutral bus. This is only in the MAIN PANEL.
 
  #38  
Old 08-26-15, 09:37 PM
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CasualJoe,

Correct. My bad I forget that the standard Main Panels most of you use have only the Neutral bus bar by default so you just terminate the GEC in there along with the Neutrals and Grounds all bonded together in the Neutral bus bar.

I mentioned the GEC to goes to the Ground bus bar because the Main Lug Panels I use from GE have both the Neutral and Ground bus bars included; however you are right the GEC termination is set by default to go in a Lug that is right adjacent to the Neutral Lug instead of the Ground Lug even in these GE models.

So now that you mentioned the need of a appropriately sized jumper, may you explain further about that term to me? What would be a good sized jumper between the Neutral and Ground in the case the GEC terminates in the Ground bus bar???


Thank you.
 
  #39  
Old 08-27-15, 10:02 AM
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JosiQDIY2015


Hi Tolyn Ironhand,

You are right in the specific context of your statement... but OP's confusion was not in that same context. He was believing that bonding both boxes could equal bonding the Subpanel Neutral to the Ground enclosure like when you use the bonding screw to bond it in the Main Panel. Problem was that OP original context was misleading and you were unable to interpret his actual confusion but I was able to do it.

And the proof of this is that after my criticisms the OP made a reply to me where at the end he stated this: ''And YES, the plastic isolator on the neutral bars was the part I missed.'' As you can see he accepted that he missed to notice the plastic isolator
I just wanted to say to Jos that you were not able to interpret my "actual confusion" and I just said I forgot about the plastic insulator (when I did not forget about it) to put an end to your so called help. My box has 2 neutral bus bars connected by an insulated jumper and a binding connector next to one of them. You could remove the jumper, and bind one of the supplied bus bars and use it as a ground bus. I chose to add my own ground bar for $5.00 more for over neatness as the box fills with circuits. My real question or as you called it "confusion" was trying to understand whether the neutral from the sub panel could actually somehow loop back as the neutral originates from the main panel and it is in fact bonded to the ground there which attaches to the sub. I think a picture would explain the answer to my question.
Thanks,
G

p.s. I think the tone of your replies to me in the past suggests you "unbonded from the wrong side of the bed".
 

Last edited by Grumple; 08-27-15 at 10:21 AM. Reason: typo
  #40  
Old 08-27-15, 10:06 AM
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Casual Joe,
I thought that only one ground connection was correct as the neutral is bonded to the ground in the service entrance or main panel? But what do I know. I guess I need to buy a newer NEC book and read some more.
Thanks,
G

Added: See page 7 of this Mike Holt PDF. I guess it does show the neutral tied to the GEC. So a jumper is code and the bond is not in the case of a GEC connected to a ground bar? I guess in that case the biggest jumper wire that fits is recommended. Just curious as although it does not pertain to my sub panel.

http://www.inspectcheck.net/client_l...vice%20Bonding

Added: Found the answer to the question about the GEC connected to the Ground Bus as opposed to the Neutral bus:
http://forums.mikeholt.com/showthread.php?t=142061
 

Last edited by Grumple; 08-27-15 at 11:08 AM. Reason: added pdf
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