Residential feeders

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sparkync

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Where is the table that use to show the allowable amperage for residential feeders located? I cannot find it where it use to be.
100 amp: #4 copper or #2 aluminum etc...

thanks
 
I would add that if you do not require any ampacity adjustments and you are on NEC 2014 or 2017 you can find the old chart in Annex D, Example D7. For the 2020 edition it has been put back in the body of the code. Remember, you can only use the chart if no ampacity adjustments are required. Otherwise you have to due the adjustments and apply the 83% rule.
 
Remember that there isn't a general allowance for residential feeders; they have to be sized the same as any other feeder.

There is a _specific_ allowance for feeders that supply the _entire_ load of a dwelling, along with various details that sometimes apply to feeders that supply part of the load of a dwelling.

-Jon
 
I still can't find the table I'm looking for, but I've got a job where a # 4 or #6 cable is pulled to a heat panel under the house and has a 100 amp breaker on it. I know the #6 is wrong, but according to the table I can't find, the #4 is good for 100 amps for a feeder. I haven't seen the labeling on the "jacket" of the wire, but just in case it is a #4, will it work in this case?
Thanks
 
sparkync said:
I still can't find the table I'm looking for, but I've got a job where a # 4 or #6 cable is pulled to a heat panel under the house and has a 100 amp breaker on it. I know the #6 is wrong, but according to the table I can't find, the #4 is good for 100 amps for a feeder. I haven't seen the labeling on the "jacket" of the wire, but just in case it is a #4, will it work in this case?
Thanks
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Neither one of those cables are rated for a 100-amp feeder.
 
You are in NC so in the 2017 here is the table Table 310.15(B)(16)

You cannot use the residential tables as that was for services not sub panel feeders unless they carry the total load of the house.
 
A 100 amp panel needs #2 copper not #4 copper. This is not service work.

2nd-- what is the load required. You may be able to leave the wire and reduce the breaker size.
 
Here is an explanation of the vanishing table:

310.12 Single-Phase Dwelling Services and Feeders.

New Table 310.12.
www.electricallicenserenewal.com

Basically, rather than having a table giving fixed conductor sizes, they changed to the '83% rule', meaning that for conductors supplying the _entire load_ of a dwelling you could use conductors that had an ampacity of 83% of the breaker rating. For example, if you had a 200A service, you could use conductors with an ampacity of 166A.

If you worked through the numbers, for 'normal situations' you would get conductors sized the same as the old table.

But the key for the OP is that the feeder being discussed does _not_ supply the entire load of a dwelling, and thus this rule (or the old table) would not apply.

-Jon
 
They ran a #4 or #6 under the house to a subpanel, then they got a 60 amp AHU under the house out of that panel, then they're feeding a 30 amp. heat pump outside.
This is coming from a100 amp breaker in the main panel outside.
 
Check to make sure, you are saying a #6 or #4, if it is a #4 you can simply change the breaker to a 80.

Roger
 
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