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Old 02-13-2010, 07:34 PM   #1
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Default 2-meter 100 amp service

Hey guys, we're arguing with an inspector on a duplex house we're doing.
This job is two 700SF houses on one lot, two addresses. Now, I know every residential service needs to be 100A, no less, but there is an exception ( i cant remember the art number, that states if two or more service disconnects are in one enclosure, then they can be less than 100A.
With the load calculations, each house needs no more than 50A and 60A, respectively.

So we have one two-meter 100A service enclosure, with a 50A 2P and a 60A 2P feeding subpanels on each dwelling. Inspector is calling for 100A on each house, even though each house does not have a service.

I'm interpretting the code as a SERVICE (of which there is only one on the lot) needs 100A. It has it. But each dwelling is fed off of a 50 or 60.

Who's right?

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Old 02-13-2010, 08:37 PM   #2
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Unfortunately not you. As you stated yourself that a 100 amp service is required per house (dwelling). I don't know the NEC article off hand but, each structure can only have one service unless special permission has been approved. So one service point to the structure/multiple meters (one for each dwelling/residence with a minimum 100 amp service to each.

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Old 02-13-2010, 08:43 PM   #3
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Originally Posted by rlc3854 View Post
Unfortunately not you. As you stated yourself that a 100 amp service is required per house (dwelling). I don't know the NEC article off hand but, each structure can only have one service unless special permission has been approved. So one service point to the structure/multiple meters (one for each dwelling/residence with a minimum 100 amp service to each.
Not true. I do apartment buildings all the time, often with a 6 or 8 hundred amp service, but only 30 amp tenant breakers.
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Old 02-13-2010, 08:44 PM   #4
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Sparky, Are you saying that you have 2 two pole breakers on each side, with no main.
Because this sounds okay as long as the service is sized correctly. And you have six or less grouped.
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Old 02-13-2010, 08:45 PM   #5
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Uh oh. You might have to do a redo.
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Old 02-13-2010, 08:47 PM   #6
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Technically I would say you are correct if the disconnect is rated 100 amps. Article 230.79(C) states this clear but I would imagine most inspectors will not see it that way.

Quote:
230.79 Rating of Service Disconnecting Means.
The service disconnecting means shall have a rating not less than the calculated load to be carried, determined in accordance with Part III, IV, or V of Article 220, as applicable. In no case shall the rating be lower than specified in 230.79(A), (B), (C), or (D).
(C) One-Family Dwellings. For a one-family dwelling, the service disconnecting means shall have a rating of not less than 100 amperes, 3-wire.

This does not say the se conductors must be rated 100 amps.
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Old 02-13-2010, 08:48 PM   #7
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there both right, but, I think since it's two address's that's causing the need for 2x100's. The one address and apt's are just based of calculated load from what little I know. I thought I saw somewhere that a single family residence needs a min of 60 amps?? Is it 60 or 100 ?? Code Ref?
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Old 02-13-2010, 08:51 PM   #8
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Quote:
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there both right, but, I think since it's two address's that's causing the need for 2x100's. The one address and apt's are just based of calculated load from what little I know. I thought I saw somewhere that a single family residence needs a min of 60 amps?? Is it 60 or 100 ?? Code Ref?
Read my post above yours. 230.79
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Old 02-13-2010, 08:52 PM   #9
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there both right, but, i think since it's two address's that's causing the need for 2x100's. The one address and apt's are just based of calculated load from what little i know. I thought i saw somewhere that a single family residence needs a min of 60 amps?? Is it 60 or 100 ?? Code ref?

100. 230.79(c).
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Old 02-13-2010, 08:57 PM   #10
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Whether the building has one address or two, a duplex is a two family dwelling. The building code makes that clear. The 100 amp minimum for a single family dwelling does not apply.

IF, these are two seperate structures, fed off a remote meter setup someplace on the lot, then you have a problem. If it's not a duplex, but two seperate and freestanding dwellings, you need 100 amp to each.
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Last edited by MDShunk; 02-13-2010 at 08:59 PM.
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Old 02-13-2010, 08:59 PM   #11
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........The 100 amp minimum for a single family dwelling does not apply.

?????

230.79(C) One-Family Dwellings. For a one-family dwelling, the service disconnecting means shall have a rating of not less than 100 amperes, 3-wire.
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Old 02-13-2010, 08:59 PM   #12
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Not true. I do apartment buildings all the time, often with a 6 or 8 hundred amp service, but only 30 amp tenant breakers.

So are you saying that a new modern apartment can be supplied with only a 30 amp service? This is a unit that HVAC, cooking and washing appliances and water heater? How small are the units?
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Old 02-13-2010, 09:02 PM   #13
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Originally Posted by 480sparky View Post
?????

230.79(C) One-Family Dwellings. For a one-family dwelling, the service disconnecting means shall have a rating of not less than 100 amperes, 3-wire.
He described it as a duplex, with one service. A duplex is a Two-Family Dwelling.
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Old 02-13-2010, 09:04 PM   #14
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Originally Posted by rlc3854 View Post
So are you saying that a new modern apartment can be supplied with only a 30 amp service?
Can't recall having ever said such a thing.
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Old 02-13-2010, 09:04 PM   #15
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I agree with Marc. 100 amp per unit not required in this scenario.
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Old 02-13-2010, 09:10 PM   #16
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Here's a picture http://yfrog.com/0velectricservicej
It's a two meter panel, rated for 100 amps. It's one service and one service drop for the two homes, and this in itself is allowed by Los Angeles and the POCO. Load calcs for square footage, appliances, etc come out to 41 amps and 50 amps for the two houses. They are separate houses. Each meter feeds a 50 and 60 amp two pole breaker, respectively. And you are allowed to rate for 125% for the service. There is no 100A main, as this would kill both meters(and houses)

Article 230.80 states " Where the service disconnecting means consist of more than one switch or circuit breaker, as permitted by 230.71, the combined ratings of all the switches used shall not be less than the rating required in 230.79" That's what we are arguing with.

It's only one service, and yes the service is 100 amp.

Last edited by SparkYZ; 02-13-2010 at 09:20 PM.
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Old 02-13-2010, 09:11 PM   #17
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Originally Posted by MDShunk View Post
Whether the building has one address or two, a duplex is a two family dwelling. The building code makes that clear. The 100 amp minimum for a single family dwelling does not apply.

IF, these are two seperate structures, fed off a remote meter setup someplace on the lot, then you have a problem. If it's not a duplex, but two seperate and freestanding dwellings, you need 100 amp to each.
The two meter panel is on one of the houses. The POCO and Building inspectors allowed this.
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Old 02-13-2010, 09:16 PM   #18
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Okay, now you're contracdicting yourself. Is this a duplex or two seperate single-family dwellings?

If this is two single family dwellings, and not a duplex (2-family dwelling), then you absolutely need 100 amp to each dwelling.

I see in your added post that you put the service on one house, and that there is a seperate house also. This is two, single family dwellings. You need 100 amp to each; no way around it. This is not a duplex, as you described it earlier.
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Last edited by MDShunk; 02-13-2010 at 09:19 PM.
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Old 02-13-2010, 09:23 PM   #19
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The two meter panel is on one of the houses. The POCO and Building inspectors allowed this.
So is it one structure seperated by a common wall (fire) as a duplex? Or is it two seperate structures such as a detacted garage converted to a dwelling?
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Old 02-13-2010, 09:23 PM   #20
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Quote:
Originally Posted by MDShunk View Post
He described it as a duplex, with one service. A duplex is a Two-Family Dwelling.
And you were making reference to a SFD.

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