Code requirements for a sub panel? (location)

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Old 05-13-04, 12:50 PM
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Code requirements for a sub panel? (location)

I moved into a 100 old house in the fall and rewired as much of the K & T as I could before the cold weather kicked in but now I need to tackle the rest of it so I can sleep better at night. The problem is that this is not an easy house to run wires. It's a small house with basically zero open walls. The only wall that I have found that is actually open from the basent to the attic is on the opposite corner from where the main panel is in the basement.

So I either have to run 8 or 10 sheathed cables from the panel to the attic and back down to the drops or find a place to put a sub panel.

The pros to keeping all in one panel is; keeping it all in one panel and not having to find a place on the second floor for a sub panel. The cons are; not being able to easily add a circuit later & if you saw how tight my basement is you would much rather struggle getting one smallish feeder to a sub than finding space in the joists for 8 - 12 sheathed cables (I like separate circuits)

Sub Panel - Pros, one pull to the panel with easy distribution. Less Voltage drop. Cons - NO PLACE to put it. The open wall is the main wall of the bedroom. Not someplace I'd like to stare at a panel everyday. Not allowed in closet right? Can't hang a picture over it right?

The big question: Can I put it in the attic? The attic has an easy pull down stair. No folding, just pull it down, grab the stairs and they roll right down to your feet. I'd like to put it right at the top of these but I don't know if that meets code. The only thing I see is that it must be "readily accessible". Who makes that determination? Does it make a difference since you could always go to the basement and shut the sub breaker off?

The second floor in question only has two bedrooms and one tiny bedroom and one tiny bath. Plus the stand up attic. Shouldn't really need much current up there except I will probably put in central air with the air handler in the attic. I have no idea how much current they need and I haven't had time to look into that yet.

Sorry this is so long but I've been flip flopping all winter over which route to go so I though I'd get some input from the "net" I've also been reading the code book till my head hurts. I feel very sorry for the commercial electricians out there.

Thanks much advance.
 

Last edited by speedy72; 05-13-04 at 01:00 PM.
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Old 05-13-04, 01:03 PM
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Can't hang a picture over it right?
Wrong. You can hang a picture over. You can put a door in front of it as long as the panel cover can opened to 90 degrees.
The clearence requirements for a sub panel are 30" wide 36" out from the front of the panel and 6'7" tall. If you have a space this size in your attic then it should be OK to install it there. Is the attic a walkup attic with a floor? If it is not then you probably can't install it there.
 
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Old 05-13-04, 02:05 PM
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Is that 30" across the panel or 30" from each outer edge. In other words 30" total or more like 75", 30" on either side and 15" for the panel? I think I can find that in the attic & it is a full floor but you have to pull down the stairs. Then it's fairly walk up, handrail and all.
 
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Old 05-13-04, 04:45 PM
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It's 30 inches total. They want enough space for someone to stand in front of the panel and work on it.
 
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Old 05-13-04, 05:16 PM
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An important consideration about locating a subpanel in an attic: circuit breakers are temperature sensitive. If they are in a hot environment, they will be subject to nuisance tripping.

-Jon
 
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Old 05-14-04, 08:50 AM
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Temperature sensitive? I thought all modern breakers had a temperature compensation builit into them? the intention is to insulate the attic to create a somewhat environmentally controlled storage space and play area for the nephews. Zoned heat of some sort and a single duct of the AC when that goes in next year.

So what about the pull down stair? Any inspectors on this site? Would you approve it? I think I would as it really is pretty easy to get to and I'm going to have emergency lighting in the area but I'm not sure I'd stake my inspection license on it.
 
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Old 05-14-04, 09:31 AM
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I might be missing something somewhere in the code, but IMHO, a strict interpretation of "Readily Accessible" would allow you to put a panel in an attic area accessed by a pull-down ladder. The definition of "Readily Accessible" has a specific reference to not allowing access by "resorting to portable ladders" which would seem to inherently permit access by a fixed-in-place device such as an attic pull-down stairs.

Besides, all power to the sub-panel can be interrupted by a breaker in the main panel which IS readily accessible.
 
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Old 05-14-04, 10:24 AM
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I am pretty certain that modern circuit breakers are intentionally not thermally compensated. That way, if the ambient conditions are much warmer than normal, the circuit breaker will trip at reduced current levels, to prevent the conductor from overheating.

-Jon
 
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Old 05-14-04, 10:30 AM
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Do you know where the reference to portable ladders is? I saw it once but haven't been able to find it again.

240.30 (B) says that the operating handle of the breaker must be accessible without opening a door or cover? What do you call the door on the sub panel?

110.26 E has an exception for the height requirement for existing dwellings so it would seem that as long as I has 30" width and 36" of depth I should be fine as long as we all consider a pull down stair "readily accesable"

I guess it's time to call the local inspector and see what he considers readily accessible but I wanted to be prepared with a good argument. I know the guy a little bit. He takes the code very seriously but he also likes a good argument.
 
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Old 05-14-04, 10:44 AM
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Originally Posted by winnie
I am pretty certain that modern circuit breakers are intentionally not thermally compensated. That way, if the ambient conditions are much warmer than normal, the circuit breaker will trip at reduced current levels, to prevent the conductor from overheating.

-Jon
I was definately taught that they were temperature compensated as they can see a significant temp swing, even in a basement. It doesn't say anything in the code that I can find though, so I'd have to ask the manufacturer. I was told the built in protection is from using 90C conductors with breakers that trip at the 60C rating. For instance a 14/2 is rated at 25 Amps for a 90C conductor but we OCP them at 15 Amps. That's only running at 60% of capacity.
 
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Old 05-14-04, 11:26 AM
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240.30 (B) says "The operating handle of a circuit breaker shall be permitted to be accessible without opening a door or cover.

That's quite a bit different than "must be accessible without opening a door or cover"

The reference to portable ladders is in Article 100 - Definitions in the definition for Accessible, Readily.

There's a sign at the local building inspections department that goes something like this "You need to realize that arguing with a building inspector is like fighting with a pig in the mud. The pig enjoys it."
 

Last edited by txdiyguy; 05-14-04 at 11:42 AM.
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Old 05-14-04, 11:48 AM
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There's a sign at the local building inspections department that goes something like this "You need to realize that arguing with a building inspector is like fighting with a pig in the mud. The pig enjoys it."
That's great!!

Thanks for the info.
 

Last edited by John Nelson; 05-14-04 at 12:37 PM.
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