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Multiple Sub Panel Installation

17K views 26 replies 12 participants last post by  Andy in ATL 
#1 ·
I have a question regarding the use of multiple sub panels. We have a detached garage without electricity and I installed two sub panels this weekend and installed a few outlets (all GFI protected) and regular light bulb outlets in garage. The reason for two sub panels: The main box inside the house is a 100 amp box with all of the circuits used, so in order to make room for a 40 amp double pole breaker for a sub panel, I installed a sub panel next to the main panel and moved two 120v circuits to the sub panel (used #8 wire as the feed). This provided the room I needed for the sub panel breaker in the main box. I then ran 100 feet of #8 wire out of the house into PVC pipe to the garage. I attached the #8 cable into the sub panel in the house on the same lugs as the feeder #8 cable from the Main panel. I used 4 breakers in the garage (very much overkill for circuits that won't get used hardly ever. My question is: Is it OK to have connected the garage feeder wire to the sub panel next to the main panel? I know I probably should have changed out the main panel to a larger service, but that would have required removing the meter etc. and I didn't want to do that.

If anyone thinks I did something wrong, please let me know.
 
#2 ·
No problem that i see as long as you got your sub panel on a breaker it don't matter witch panel your circuits are on as long as you don't over load either of your panels. all so unless you have all gas appliance or a small trailer i would make upgrading your panel your next home improvement. 100 amp is pretty small for as much stuff we run now days.
 
#3 ·
Thanks. I thought it would be ok. One other thing. I ran the #8 cable in grey PVC to the garage. Does the #8 cable have to be weatherproof cable since it is enclosed in the PVC? I bought a roll of #8/3 wire but I don't think it was rated for direct burial. I assumed that since it would be going thru the PVC pipe, that it would be well protected from the elements.
 
#7 ·
I agree w/ Andy. The PVC is still considered a "wet" area by the NEC & thus NM cable can not be run there.

There are still many other items you need to be sure were done correctly i.e. did you keep the neutral & ground wires isolated, what is the temperature rating of the cable/wire (can't use the ROMEX anyway), how deep is the trench, did you use ground rods & how were they installed, etc?
 
#10 ·
hi all.........I've seen the comments about electrical cable run thru glued pvc on here before, and was hoping someone could explain the reason a little more in depth.........not arguing the code, just would really appreciate more info, cuz' like many others it seems to me that in a sealed dry plastic conduit is not out in the wet location, be it in a crawl space, attic, garage, or shallow trench.........??
 
#11 ·
hi all.........I've seen the comments about electrical cable run thru glued pvc on here before, and was hoping someone could explain the reason a little more in depth.........not arguing the code, just would really appreciate more info, cuz' like many others it seems to me that in a sealed dry plastic conduit is not out in the wet location, be it in a crawl space, attic, garage, or shallow trench.........??
Wire insulation and cables are rated for location among other things. Inside a conduit - be it running through an attic or underground to a garage is NOT a location. Underground is underground. Outside in the weather strapped to the side of a building is outdoors. Running through a basement is indoors - running through an unheated damp carwl space is a moist location.

If you think the interior of a conduit buried underground constitutes "indoors" you would be wrong. It WILL get wet inside that pipe. It's not hermetically sealed. It's not protected against the enviroment that envelpes it.
 
#13 ·
.........OK that makes sense then.......particularly about the condensation forming inside the conduit, I appreciate your time & patience in explaining that, rather than just the typical " don't do that, its stupid and wrong and you will die" response some like to give. What exactly does the moisture do to the wires anyway that the insulation does not protect them from.....or is it just the fact that IF there were a break in the insulation it would cause a short circuit?.....
........trying to learn here & you guys seem to be very knowledgable and willing to share information.........local electricians won's answer questions for homeowners much.just want their $$$$ to come & offer an estimate to do the work themselves......so this is really appreciated..........you guys help us DIYers out, and keep us safe..........knowing we're probably going to try to tackle the job anyway, so we might as well be educated as much as possible about it...........
If ever through the Atlanta area for business, I'll take you & your family out to dinner Andy!
 
#14 ·
PB,

My opinion and my opinion only... The romex is not listed or allowed in the conduit. The code is clear on that. The type wire typically used in PVC is THHN/THWN. Go to your home center and take a piece of #12 THHN/THWN and a piece of #12 romex and compare them.:whistling2: Not much difference, but that doesn't change the fact that it is against the rules. Thanks for the dinner offer, Andy likes food.:laughing:
 
#15 ·
Andy - can "outdoor' romex ( sorry I forget the correct term, but the kind rated for direct burial) be placed inside PVC for added protection in an outdoor environment ?

I'm referring specifically to 12 and 10, I've never seen it in higher sizes.

I looked at other web sites, and this topic get a lot of discussion.

Thanks !
 
#16 ·
You are probably referring to UF cable. In most cases it can be used & routed inside PVC however most professionals would pull separate THHN/THWN conductors. Also it can be a pain to pull UF cable in conduit but it can be done.

In some cases, like some motor applications the ground must be insulated which is not the case w/ UF cable & could not be used.
 
#17 ·
I have done this for many years including stack in shakes ,kfc's ,Abby's etc. all passed code with flying colors. Now i tried to put on hear after my last post that it might not be code but it wasn't letting it post. But seriously most guys that's done this for years wouldn't sweet this. Now if it seriously is scarring you then pull it out and go spend some money and get new wire. But I'll tell you what. About 2 months ago i re barred a cable for a garage so he could run a bigger service. His old wire was good old standard romex barred directly in the ground. After telling him how bad that is he told me its been there for 8 years and it still looked new. So to sum it up he must not be rich or he would have change his panel out. He already bout the wire and for a working man wire is expensive. you could argue with me all day but from my experience I'll tell you PVC dose prevent Walter. I don't care what some pencil pusher trying to get his code in the books say. To this day i work with a lot of under ground and have yet had a wet mouse in buildings that's been there for 40 and 50 years. Now if i was putting it in no i wouldn't of bout that kind of wire how ever if it was putting it on my house and that was the wire i already had. I would use it. Now if you want me to play businessman electrician then pull it out call a electrician and pay him $90 dollars an hour then "i don't know where you live" but get all the permits needed then after he juiced you for 8 hours call in the inspector to inspect it and the end result you still have power to the same place.
 
#20 · (Edited)
Handyman 2007

Please disregard anything told to you by this poster "Drennen'. Occassionally we get people like this on all forums that pass themselves off as people with years and years of experience and so on and so forth. Then proceed to tell you a mouthful of inaccurate and non-code compliant information. You do not run nm-b in an underground conduit and there is not an inspector I have ever met that would pass it. Conduits that are underground can fill with water for various reasons. If the cable or individual wire is not rated to be in a wet location it cannot be in a wet location for good reason. You can not guarantee that a conduit will not fill with water if it is underground.....glued or not. To be more clear you never expect or intentionally install any wire in water... the exception being well pump wire. Wet location means that the area is at risk of becoming wet. Nm-b is not rated by the manufacturer to be in a wet environment or it will likely fail especially if wet continuously in a conduit. The outer jacket nor the conductors are coated with nylon polymide for wet application. The conductors of nm-b are thhn only... not thwn as would be required for wet application.
There are a host of questions that need to be asked on your installation in leau of the things you have told us. As mentioned earlier it would appear you have two mlo sub-panels connected with the same feeder and using single wire lugs on the first downstream sub-panel to join the second feeder by placing both wires under these single wire rated lugs. You very likely will run the risk of a loose connection at these lugs. I would also like to know what size conduit you used. And as asked earlier did you keep neutral and ground separated in your sub-panels? How deep is your trench etc etc etc....
 
#22 ·
If the cable or individual wire is not rated to be in a wet location it cannot be in a wet location for good reason. You can not guarantee that a conduit will not fill with water if it is underground.....glued or not.
Stubbie, you old pro, I have to disagree with you on this one statement.

In my experience it is more accurate to say that any conduit run underground will most likely get water in it.

In 20 years, and haveing done quite a bit of retro fit work, I cannot remember pulling old wire out of a conduit dry. In fact even in new work if several weeks pass between when the conduit is run and when the wires are pulled, there is already water in the pipe.
 
#23 ·
.........Ok, so it appears that, from the majority of professionals on here, the issue is moisture, and that the insulation on standard NM-B is not waterproof plastic, as it needs to be, like on the THHN/THWN.........that's what I was wondering about.............not the "code this"..."20 years that"......personal opinion answers, but the real reason for the code in the first place.
 
#24 ·
Jwhite

Yes I would agree that I was inaccurate in stating that the wet location was a risk area that may fill with water. Sometimes I find myself trying to say something a little differently so that it will be more easily understood. In this case looks like I didn't do a very good job of that. A conduit will fill with water overtime and I've seen that happen too many occasions to remember. In fact I've been on call backs just a few days after an installation where the wires were damaged during the pulling process and the "glued' conduit filled with water and had a resulting phase failure. Anyway I'm glad you caught the misstatement as it was not worded as it should have been.
 
#25 · (Edited)
Jwhite

In fact I've been on call backs just a few days after an installation where the wires were damaged during the pulling process and the "glued' conduit filled with water and had a resulting phase failure.
Stubbie,

It makes you wonder why more electricians don't megger the wires after installation. I know that our British brothers test the insulation of every wire they install.

Edit to add: Inspectors in ATL have been passing romex in carflex on AC's since I got in the business. I'm not saying they are missing it...I'm saying they look at it and pass it. I'm also not saying this is right....

I'm confident when I say that 75% of the homes in this city have this code violation.
 
#26 ·
Carflex can be direct buried but I would think that would be rare in residential A/c installations. In my part of the country we use it primarily from the disconnect to the unit. And yes I have seen a bunch of romex in that situation. The manufacturer bills its fittings as water tight in the listing maybe your inspectors are using the water tight listing as voiding the wet location requirement since you likely will not have any couplings in the conduit run as it is sold in large continuous rolls instead of segments of 10 feet or less. And you do not glue it. Hard to say how they look at it but that might be part of the reason behind letting romex be installed in buried carflex.
 
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