Is a sub-panel off a sub-panel code?
My main 200 Amp electrical panel is in my garage (where my shop is!!!) and my house is fed underground via 2″ conduit off a 125 A breaker (my electrician told me I could get a 150A breaker, but only a 125 was availble in SquareD QO). I fed the house about 100′ from the garage with 3 2-00 (not 2 gauge) and 1 #4 bare copper in the 2″ conduit.
I’m running out of spaces in my sub-panel. Is it code to hang a sub-panel off of the sub-panel in my house? I’m looking for enough spaces to finish off my basement. Mostly low current stuff (lighting, computer etc).
My only alternative is to run new wires through the conduit and put a new sub-panel off the main in the garage. What’s the largest conductors (3 insulated + 1 bare ground) that I can add into the existing 2″ conduit and not violate cabel fill restrictions?
Thanks
Tim
Replies
I can' t think of any restrictions on the number of subpanels,
there is the rule of six, but you won't be running that many subs from from one panel......right ?
BTW try to forget about running more wires thru that 2"
>>I can' t think of any restrictions on the number of subpanels,I've never seen any such restriction either>>there is the rule of six, but you won't be running that many subs from from one panel......right ?The only "rule of six" I know of is (old version) "No more than 6 hand motions to turn off all power in a building" or, (new version) no more than 6 breaker or disconnects to turn off all. (New version supposedly to eliminate the old concept/interpretation that sweeping a batch of breakers with the side of your hand is an acceptable "turn it off with a hand motion" is OK)Hmmm: question: if the main panel is in building A, with a single breaker in that panel feeding a sub panel in building B, but the panel in building B doesn't itself have a single disconnect and has more than 6 breakers, is the panel in building B properly done?
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Sojourners: Christians for Justice and Peace
if the B panel is disconnecting other sub panels, than B panel would be a violation....
rjw,
Good point about the sub in the house not having a overall disconnect. I didn't even think about that. I did pull permits and everything was inspected.
Is this a "good practice" issue or a "code" issue.
TimYou buy a cheap tool twice and then you're still stuck with a cheap tool!
Maddog3
Curious, why do you say not to run extra wires through the conduit. Is this against code in any way?
I did have a concern that the wires might rub against each other during the pulling process and wear through the insulation. Of course if I did pull new wires, lots of lube wouuld be a necessity to prevent just that.
TimYou buy a cheap tool twice and then you're still stuck with a cheap tool!
not against code unles you exceed the conduit fill, but sometimes the wires twist when they are pulled in the first time ! making it very difficult to feed anything but small wire thru...
If you are going to use that conduit,the best way would be to pull out the old feeders and re-pull them (if they long enough, provided you don't cut any of them) along with your new circuits...
however, I would just pull new wire for everything and scrap out the old feeds
....how many circuits are you gong to add with your new sub ?the other problem involves derating ALL the current carrying conductors in that pipe to 80% of their ampacity,and yet the next problem ....you cannot use a panel as a junction box !!Sorry for the mixed up answers today....you can pull extra wire thru the pipe but you cannot feed them thru the existing panel..they would have to go directly to the new subEdited 11/20/2005 2:49 pm by maddog3
Edited 11/20/2005 3:16 pm by maddog3
There are a number of misconceptions running thru this thread and I would like to clarify, obfuscate and perhaps enhance their quantity in no particular order.
"What's the largest conductors (3 insulated + 1 bare ground) that I can add into the existing 2" conduit and not violate cable fill restrictions?" Only one ground is necessary in any given conduit.I ran the calculations. Three 2/0 [area .418] = 1.254" + #4 [>.042] = 1.296 sq. in. 40% of 2" PVC is 1.316 sq. in. This leaves room for one #8 at .017".
The "six disconnecting means" rule applies to the service entrance. After that, Panel B in the house and everything after it is protected by the 125 amp breaker in Panel A. As for the original question, you can have as many subpanels as you want. Series or parallel. The Code does not mention the word "subpanel". The house may need a seperate ground rod.
As far as I know, you can splice in a panel although it's not cool. But things happen. For instance, the compressor turned out to be three phase instead of the planned 220, 2 pole circuit so the time clock was spliced to an emergency lighting circuit and wires shuffled around. There is nothing against running wires through a panel except they muct not fill more than 40% of the space. Correct me if I am wrong with Code references.
~Peter
I have been having one really bad day, ....
you are right about the fill in the panels, but it sounds like his sub is a small onehowever feeding through panels around here is a no-no regardless of fill ....at least on commercial jobs, I think he should just use a feed from the sub in the house to his new sub....
there... I am now done for this day
I don't know about the NEC, but the CEC has no restrictions on the number of subs allowed.
About the disconnect stuff... that only concerns the main breaker. As a practice, I would have a main breaker on the panel in the house too. (just so's ya don't have to run to the garage to shut down the house by itself)
I would sub off the house sub with a 2P60 (or better) breaker feeding the new sub. If you take your clampmeter, you will find that there is probably plenty of ampacity left in the house panel. Just because the panel is rated for 125A doesn't mean you are pulling 125A.
As for using a panel as a raceway... That is a DEFINITE "NO-NO"!! Doesn't matter if the panel is a main or a sub... "no way Jose"!! I got stung on that when I had to install some "buck and boost"s for some rectifiers.
locolobo; Edmonton, AB
>>The "six disconnecting means" rule applies to the service entrance. After that, Panel B in the house and everything after it is protected by the 125 amp breaker in Panel A.What I was wondering about is where the main panel is in building A (the house, for example) with a breaker in the main panel for a circuit to a sub panel in another building, Building B (the garage, for example).If the subpanel in building B doesn't have a single disconnect in or on building B (that is, downstream of the main panel in building A) is it still subject to the "6 disconnect" rule? That is: If the building B subpanel has 10 circuits, say, but no "main" does the fact it can be turned off with one breaker in building A suffice?
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Sojourners: Christians for Justice and Peace
You made me read the Code this morning. Well at least sections 230 and some of 250. As far as I can tell: "If the building B subpanel has 10 circuits, say, but no "main" does the fact it can be turned off with one breaker in building A suffice?" this seems to be OK. But it would be nice to have a main breaker on the house. Also somewhere they do require a notification plate as to where the [other] source of power is located.
The purpose of requiring a disconnecting means at the service is because there is no protection from the power company's transformer until the user's service disconnect. Thus you could have 10,000 amps running amok until something vaporizes.The purpose of the six breaker rule is for the convenience of firemen. They don't want to spend all day flipping off breakers or pulling fuses.
If you want me to take this to a higher authority, I can do so.
~Peter
thanks
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Sojourners: Christians for Justice and Peace
PM22,
So if I understand your calculations correctly, the cable fill for PVC conduit is only 40%!!?? So essentially I can't pull anymore wire into the conduit without violating cable fill limitations.
As for the draw off the sub-panel. the highest draw I have is the ovens (cooktop is gas) and the air conditioning (2 ton unit). I over wired the house so no one circuit would be drawing anywhere near max. My issue is spaces not amperage. The QO panel I have does not support tandem breakers even though they fit.
So in summary what I am getting from the thread is that the best solution is a sub off the sub in the house. I do want to add a hot tub at some point but at least that is 220V so the current draw should be lower.
Thanks for the help.
TimYou buy a cheap tool twice and then you're still stuck with a cheap tool!