How many circuits/sub-panels on a 200A service?

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Old 01-08-11, 11:02 AM
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How many circuits/sub-panels on a 200A service?

The property consists of two houses, with one electrical entrance feeding a 200A breaker main panel.

A 100A breaker in the main panel feeds wires running underground to a sub panel in the other house. In the past few years available 12 spots in the main panel have been occupied with fairly low amperage breakers (few dual-pole 20A for A/C, moved well wiring from sub to main).

So I need 3 spots, tandem breakers are one option, but the box is already fairly crowded.

While I was at Home Depot yesterday the licensed electrician said a main lug panel would be a better idea (and I agree), parts to do it would be dirt cheap, I can't believe how cheap they are ($34 for a 12 spot/125A panel).

The panel would be next to the other, so only about 5' of THHN 4 gauge would be needed, with probably a 70A breaker. He said sub-panels need a separate ground and neutral from the main panel.

So, is there a maximum number of sub-panels allowed on a 200A service. I took random load readings off the legs and see about 20A combined, max 30A, I know startup loads are much more, but we are no where near peaking.
 
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Old 01-08-11, 01:12 PM
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There is no actual limit except for the available ampacity to supply the loads.
 
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Old 01-08-11, 01:42 PM
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Thanks pcboss,
I was worried there was some sort of maximum ratio of breakers to main breaker capacity.

Overall there is very little load on most breakers, I tend to go over-board with individual circuits, when I have access to bring wires through I pull many.

Another question, is there a minimum distance a panel has to be from a boiler? The boiler is about 18" from the wall, and the panel will on that wall about 5' high, next to other panels, but closer to boiler.
 
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Old 01-08-11, 02:38 PM
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You need a 30" width in which the panel does not need to be centered. The workspace must also be 36" deep and with no foreign systems in that space.
 
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Old 01-08-11, 03:49 PM
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OK, so that spot would not work since the oil burner will be in front of it.

Are there any height restrictions? Can it go under a window with a 4' high sil? So the bottom of the box will be about 2' off the ground.
 
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Old 01-08-11, 06:25 PM
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I think some would consider the window a foreign system. I would check with your building officials.

As long as the main breaker is below 6'7" to the center of the handle you are fine Code-wise. May not be convenient that low tho.
 
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Old 01-09-11, 06:09 PM
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Originally Posted by hubjeep View Post
Can it go under a window with a 4' high sil? So the bottom of the box will be about 2' off the ground.
I would consider the window a possible source of water damage to the panel, but you could check with your local inspector to see if he would approve it.
 
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Old 01-14-11, 05:15 AM
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I checked with a licensed electrician friend of mine, he said it's fine to install it there.
 
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Old 01-14-11, 07:58 AM
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Still on the fence about this, I spoke with a couple more electricians at a supply shop who said it is probably OK. Maybe I will try finding out who to call in the town to ask.
 
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Old 01-14-11, 09:37 AM
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I called the town, their inspector said it's fine, do it!
 
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