Electric Sub-Panel Installation

[tc35dforme]

Seems like a simple solution that isn't coming to me.....

I've installed many panels, but for my addition, I'll have a flush installation between studs in a wall. My question....since the panel is 14.25" wide, there will not be room for romex clamps at the box to secure the branch wiring. What am I missing ?? Do I need to header off the stud space to allow for a wider rough opening ??? Do I invert the clamps with the locking collar inside ????

Anyone have an answer to my stupid question ???

 

[TonyV]

Why can't the circuits come into the top/bottom of the box??

...Tony

 

[slowrev]

Yep, use the top and bottom of the box, I think many panels don't even have knockouts in the sides, and seem to be designed for top/bottom access only.

Ben

 

[LarryD]

Top and bottom, like Tony said. There should be knockouts across the width of both locations.

 

[timb]

On a sub-panel like that, what are the applicable rules relative to permanent access/location?

 

[Farwell]

Not a stupid question and your idea of using a header is a good idea in some applications. In most cases using the upper and lower knock-outs is the easiest and most used way but sometimes things dictate that you have to go the other route which I have done many times and it works fine.
When it comes time to run your sub-panel supply wire, if you are running 220-volts, run four wires. Two hot legs, one neutral leg and one ground (or bonding) leg. The reason I mention this is that my pole barn has the three legs running from the main and I would be more comfortable if I had the ground (or bonding ) leg running back to my main panel.

 

[BigAl]

Farwell ,
Could you not just drive a ground rod at the barn and attach a ground wire from it to your barn panel . Seems to me you would end up with the same thing as sending a ground wire all the way to the main panel as well as saving a few dollars . The building inspectors around here love more than one grounding source .
Allen

 

[tc35dforme]

Like I said...the answer was obvious, but not coming in......

The top and bottom knockouts are the answer.....never even thought..... /forums/images/graemlins/crazy.gif

Thanks for the wake up guys !!!!

 

[Farwell]

Al,
The inspectors in my area want the three leg run with the two ground rods driven 6 feet apart at the pole barn and the neutral bonded to the sub-panel along with the ground (or bonding) leg so this is the way I did it because the three legs were run and buried before I purchased the property.
You would not believe the many different opinions on this issue that I have run across.
Yes you are right it is pretty much the same thing but being **** like I am I wanted the extra insurance in case I lost the neutral leg for some reason.

 

[Farwell]

Al,
Re-read your post and wondered if you knew that the secondary ground at the sub panel needs to go back all the way to the main panel box because earth ground at the sub panel has too much resistance to work well as a path back to the third leg coming off of the electric pole transformer that is tied into the main panel and earth ground rod driven at the main supply input point. That is why the neutral and earth ground at the sub panel are bonded in the sub panel box. This is something I learned from reading Mike Holt's Grounding and Bonding information on his web site.
This is probably going to start some serious discussion but this is what I have gleaned over the past year of researching. May be wrong but it makes sense to me.

 

[Junkman]

</font><font color="blue" class="small">( .........You would not believe the many different opinions on this issue that I have run across.
................... )</font>

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]

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]

<font color="blue"> But there is only one National Electrical Code and that is what you should be referring to... </font>

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]

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]

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]

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]

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]

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]

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]

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.