Electric Sub-Panel Installation

Junkman · Jul 11, 2005

( .........You would not believe the many different opinions on this issue that I have run across.
................... )

But there is only one National Electrical Code and that is what you should be referring to, instead of asking opinion, which may or may not be correct. The separation of the neutrals and grounds are clearly spelled out when it comes to sub panels, and they are separated for a good reason. Unless your local building department specifies otherwise, follow the current National Electrical Code and you will have no problems.

Cityboyfarmer · Jul 11, 2005

The neutral circuit is designed to carry the unbalanced current of your 120vac loads. The circuit running to your barn is called a "feeder" panel and really should have a neutral conductor because you should not have the unbalanced neutral currents flowing across your grounded conductor. In a feeder circuit, the neutral and ground should not be bonded in the feeder panel.

LarryD · Jul 11, 2005

But there is only one National Electrical Code and that is what you should be referring to... 

As well as your local building codes. The NEC is a minimum standard and is "improved" upon by many states / counties.

WAC's require a grounding conductor on all subpanels as well as grounding electrodes at the panel. Your local inspector can give you all the details.

The problem arises when folks pick up a panel at the local Home Depot and install it themselves. It isn't rocket science but without a permit your only asking for trouble. I would be curious to see how many insurance companies rejected an electrical fire claim because there was no record of a permit. I for one wouldn't store hay in a bulding that isn't permitted. The local fire dept. might come back and charge me for an illegal service. /forums/images/graemlins/shocked.gif

Farwell · Jul 11, 2005

Junkman,
Local code requires that the neutral and earth ground be bonded in the sub-panel. Not really sure of the reason unless it is because the building is separated from the main structure and there is only the three wires coming from the main. As I said in my earlier post this issue will start a discussion and sometimes a very heated discussion. I had to go with the local code and not with the National Electric Code against my better judgement.

Cityboyfarmer · Jul 12, 2005

Farwell,

You absolutely have to go with what the authority having jurisdiction (AHD) ie: your local inspector, says. I know from professional experience that it does not pay in most cases to argue with your inspector. I have watched my fellow electricians and HVAC contractors argue with inspectors with little success over the years. I learned early on to cultivate a good working relationship with inspectors.

Heated arguments? Nah. Not me. Continuing education is the answer for inspectors as well as electricians. That would eliminate much of the controversy surrounding grounding. Most guys stop updating their education once they get their "card". I have taken courses on grounding even after becoming licensed and still find the subject fascinating. (Yeah, I know. /forums/images/graemlins/smirk.gif)

As to the 3 wire system, there are lots of them out there that have functioned with no problem for scores of years and will likely continue to do so. The grounding system comes into play when you actually do encounter a problem or hazard and can be the difference in being protected or having an empty lot...or worse.

Electricity is a subject to learn about...not argue about /forums/images/graemlins/smile.gif

renz · Jul 12, 2005

I'd get the final word from a licensed electrician but that said:
It is SOP to remove the bond between ground and neutral in a subpanel to isolate them. For reasons of 'easiest path' I haven't bothered to fully study and understand, I know that if the neutral and ground are left bonded in a subpanel, the possibility exists of a fault energizing any and all metal - ductwork, for example - connected indirectly to the ground side of the electrical system.

Junkman · Jul 12, 2005

The real question is "is it local code?" or is it the opinion of the local code enforcement officer? I know that some local code regulations are more stringent than the National Code, but I never heard of the local code being in complete contradiction to the National Code. Since I have no experience in this beyond what was required by my local building department and the local utility, I can't comment beyond that experience. In this one instance, I was told that the neutrals and the grounds MUST be separated. I did it that way, and that was also the way of the National Electrical Code.

Farwell · Jul 12, 2005

Renz,
After the local inspector required the bonding at the sub panel I contacted a local licensed electrician and he said that is the way it is done in our county, and I bugged him for a few minutes in order to make sure that I understood him correctly

Farwell · Jul 12, 2005

Junkman,
I have an older version of the NEC and that is how I initially wired the sub panel and because I have had building inspector experiences where they made decisions based on personal opinions rather than common sence and was worried that the electrical inspector may be similar is the reason I contacted the licensed electrician. Maybe I will separate the neutral and ground at the sub panel, if I have a fire quickly re bond them again. Tee! Hee! Thanks for the input, sorry if I occupied this thread too much.

Inspector507 · Jul 12, 2005

There seems to be a discussion on 2 or 3 different subjects going on in this thread. The others have already suggested using the top and bottom KO's in the panel box. Good suggestion. Item one solved.
Item 2.....
When running a sub-panel feed to an addition or ATTACHED garage, the NEC® requires a 4-wire feeder with all grounds and neutrals separated at the sub-panel. Now local codes could prevail, so check your with your local authority if you have one. Item 2 solved.

Item 3.......
When running a feeder to the barn or other DETACHED structure, you are permitted to do it as in Item 2, with the addition of a grounding electrode connected to the grounding conductor coming from the main supply.
You are also permitted to run a 3-wire feed the the detached structure. The grounded conductor(neutral) must be connected to a grounding electrode and bonded to the panel cabinet. All of this applies if you have no continous metallic paths between the 2 structures, such as metal water lines, metal conduit, etc.

The above information is based on the NEC® and may be different if local codes are in effect.