dwelling vs. office space etc.

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t wheeler

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The code requires #2 ALLUM. for a 100 amp sub-panel in a dwelling. Is this also the case in an office space or gift shop?
 
There has been much debate as to whether or not you could use table 310.15(B)(6) for a subpanel in a dwelling. You can not use that table for an office or gift shop.
 
Where did you get the notion that the code "requires" #2 aluminum? The NEC certainly does not. What is the nature of the existing installation or the new project you are discussing?
 
charlie b said:
Where did you get the notion that the code "requires" #2 aluminum? The NEC certainly does not. What is the nature of the existing installation or the new project you are discussing?
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Article 310.15(A)(6) is for 120/240 volt, single phase dwelling services and feeders. The table 310.15 shows #2 aluminum for 100 amps. This section does not apply to non-dwelling units.
 
pismo said:
Article 310.15(A)(6) is for 120/240 volt, single phase dwelling services and feeders. The table 310.15 shows #2 aluminum for 100 amps. This section does not apply to non-dwelling units.
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Wow I agree pismo. Nice to see you again.
 
pismo said:
charlie b said:
Where did you get the notion that the code "requires" #2 aluminum? The NEC certainly does not.
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The table 310.15 shows #2 aluminum for 100 amps.
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[/quote]

It may "show" it, but it does not "require" it ;)
CU would also be allowed.
 
I would like to use Allum. due to cost purposes. I would like to know what table or section addresses this for a non-dwelling applications...and what size is permissable.
 
celtic said:
It may "show" it, but it does not "require" it. CU would also be allowed.
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My point exactly. It also does not prohibit using 4/0 aluminum, though I doubt many would choose to do that. What the code "requires" is that we not use anything with a lower ampacity, unless that other thing is described as being acceptable for that application in some other applicable article or table. The code gives minimums, not absolutes.
 
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t wheeler said:
I would like to know what table or section addresses this for a non-dwelling applications...and what size is permissable.
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Table 310.16.

But I can't tell you the minimum size required for the application. You must start with a calculation of the load that the sub-panel will carry. It is not sufficient to say that it's a 100 amp panel, because you might have inadvertently installed more than 100 amps of load. But you might actually have a much lower calculated load than 100 amps, and that would allow you to use a smaller feeder conductor. So you really need to do the calculation first.



Table 310.15(B)(6) allows the use of smaller conductors than Table 310.16. But it applies only to dwelling units.
 
t wheeler said:
I would like to know what table or section addresses this for a non-dwelling applications...and what size is permissable.
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310.16

..but you also to need to know that the panel is not under-rated at the 100A (aka, load calculation) and depending, on the distance from the main panel, any allowance for voltage drop.
 
The runs will be about 75ft. to the sub-panel located in the office, 2- 20 amp recp. circuits[8 outlets each], and 1 lighting circuit only. The customer already has a 100 amp panel that he wants to use.
 

It may "show" it, but it does not "require" it ;)
CU would also be allowed.[/QUOTE]
The code is just a minimum. That means #2 aluminum is the minimum.
 
pismo said:
Article 310.15(A)(6) is for 120/240 volt, single phase dwelling services and feeders. The table 310.15 shows #2 aluminum for 100 amps. This section does not apply to non-dwelling units.
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I would also point out that a sub-panel (meaning a "real" sub-panel, not a main-lug "main" panel fed from a remote main disconnect) also does not qualify, even residential, and #2 al is limited to 90 amps. Here's why I say that; note quoted text:

[quote='02 NEC]310.15(B)(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders.
For dwelling units, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service lateral conductors, and "feeder conductors that serve as the main power feeder to a dwelling unit" and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboard(s).[/quote]
Now, to me, this disqualifies any feeder fed from a panel which is itself fed by "the main power feeder", so a 100 amp sub-panel requires larger than #2 al, regardless of the expected load.

The weakest link controls the show. The panel used, as well as the cable used, must both be rated at least as high as the breaker used. Expected load does not apply here.
 
celtic said:
You sure about that....couldn't #4 CU also be considered the "minimum"?;)
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No, but #3 could.

As above, only " the feeder conductors that serve as the main power feeder to a dwelling unit" may use table 310.15(B)(2)(a); all other uses need to use Table 310.16.
 
LarryFine said:
No, but #3 could.

As above, only " the feeder conductors that serve as the main power feeder to a dwelling unit" may use table 310.15(B)(2)(a); all other uses need to use Table 310.16.
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310.15 says dwelling services and feeders.
 
pismo said:
310.15 says dwelling services and feeders.
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You have to read further into 310.15(B)(6) to see that only feeders considered as Main Power Feeders as defined in the section can use the reduction, not all feeders meet this definition.

(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders For individual dwelling units of one family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboards(s). The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.
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Roger
 
roger said:
You have to read further into 310.15(B)(6) to see that only feeders considered as Main Power Feeders as defined in the section can use the reduction, not all feeders meet this definition.



Roger
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So what you are saying is I can, for example use the #2 al. for my service entrance, then use table 310.16 for a sub-panel? This would mean from the service I would have to use 1/0 al? I read the entire section. The second to last sentence says " the feeder conductors to a dwelling unit shall not be required to be larger than the service entrance conductors." With that said, the #2 al. would be adequate for the 100 amp sub.
 
pismo said:
So what you are saying is I can, for example use the #2 al. for my service entrance, then use table 310.16 for a sub-panel? [
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That is correct if the downstream panel is fed from a "Lighting and Appliance Branch-Circuit Panelboard".

pismo said:
This would mean from the service I would have to use 1/0 al?
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If the downstream panel is a "Lighting and Appliance Branch-Circuit Panelboard" and is fed from the Main Disconnect (as in Service) it can use 310.15(B)(6) in that the feeder would meet the definition of a Main Power Feeder.


pismo said:
I read the entire section. The second to last sentence says " the feeder conductors to a dwelling unit shall not be required to be larger than the service entrance conductors." With that said, the #2 al. would be adequate for the 100 amp sub.
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Well, since these feeder conductors are "to a dwelling unit" it would seem as though by the wording itself it is referring to a Main Power Feeder, not a sub-fed downstream panel.

If the paragraph used wording such as "to a pump" it would it would cover more than just a Main Power Feeder.

Roger
 
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