Is 4/0 AL SER good for 200A in NC?

[Buck Parrish]

Is 4/0 AL SER still good for 200 amps in an SFD in NC? It will pass through about 4 ft of insulation in a wall as it comes down to the panel.

Is 2/0 CU THHN in conduit still good for 200A in an SFD in NC ?

 

[Buck Parrish]

It's for a 200A sub panel.

 

[letgomywago]

Does it feed the whole dwelling?

 

[Buck Parrish]

Does it feed the whole dwelling?

No

 

[wwhitney]

NC apparently uses the 2020 NEC. So insulation contact with SER cable is only an issue for sizes #10 AWG and smaller.

For outside of single family dwellings, #4/0 Al has a 75C ampacity of 180A, so it may be used for a load of up to 180A and protected at 200A. Likewise #2/0 Cu has a 75C ampacity of 175A, so it may be used for a load of up to 175A, and needs to be protected at 175A at most.

For a SFD supplied at 200A (via a service or feeder that carries the entire load), then those conductors, and any further downstream conductors, need only have an ampacity of 83% * 200A = 166A. In this context, both #4/0 Al and #2/0 Cu may be used for a load of up to 200A and protected at 200A.

However, if the SFD is supplied by more than 200A, then that 83% allowance would not apply to 200A and smaller feeders, and the usual non-dwelling unit limits would apply to #4/0 Al and #2/0 Cu.

Cheers, Wayne

 

[Buck Parrish]

NC apparently uses the 2020 NEC. So insulation contact with SER cable is only an issue for sizes #10 AWG and smaller.

For outside of single family dwellings, #4/0 Al has a 75C ampacity of 180A, so it may be used for a load of up to 180A and protected at 200A. Likewise #2/0 Cu has a 75C ampacity of 175A, so it may be used for a load of up to 175A, and needs to be protected at 175A at most.

For a SFD supplied at 200A (via a service or feeder that carries the entire load), then those conductors, and any further downstream conductors, need only have an ampacity of 83% * 200A = 166A. In this context, both #4/0 Al and #2/0 Cu may be used for a load of up to 200A and protected at 200A.

However, if the SFD is supplied by more than 200A, then that 83% allowance would not apply to 200A and smaller feeders, and the usual non-dwelling unit limits would apply to #4/0 Al and #2/0 Cu.

Cheers, Wayne

Thanks Wayne, you're alright. I'm going to set a meter base combo outside and feed my shed and an outside outlet or two. Then on to the inside 200 amp main lug panel.
I thought NC might have some amendments that still allowed 4/0 AL or 2/0 CU to still be used to a 200A sub panel not carrying the entire load of the SFD.

 

[wwhitney]

I thought NC might have some amendments that still allowed 4/0 AL or 2/0 CU to still be used to a 200A sub panel not carrying the entire load of the SFD.

Well to repeat the NEC still allows that if the service (or main feeder) for the dwelling unit is 200A. As then that supply is allowed to be 4/0 Al or 2/0 Cu, and there's no point requiring an increase in conductor size further downstream.

Cheers, Wayne

 

[letgomywago]

If the outside stuff is not attached to the dwelling then you're good to go it's only if you have a few circuits in the meter main that it doesn't completely fly

 

[wwhitney]

If the outside stuff is not attached to the dwelling then you're good to go it's only if you have a few circuits in the meter main that it doesn't completely fly

If it's a 200A service, how does that matter?

Cheers, Wayne

 

[letgomywago]

If it's a 200A service, how does that matter?

Cheers, Wayne

An entire dwelling as what's is defined in the NEC can take advantage of this. I've used this to be able to put an ADU on 2 SER with a 100 amp breaker ahead of it. If you have an adu with a house and the meter main outside load calc meets up with a 200 amp service you can use this provision for the feeders to each dwelling. Or if you have a detached garage with an 8 space meter main the feeder to the house from the garage can be 4/0 using this.

 

[wwhitney]

If you have an adu with a house and the meter main outside load calc meets up with a 200 amp service you can use this provision for the feeders to each dwelling.

Certainly; although then you can't use 310.12 on the service conductors themselves. Plus there is some debate as to whether the service load may be taken to be just the sum of the 220.82 optional load calcs of the two dwelling units.

Or if you have a detached garage with an 8 space meter main the feeder to the house from the garage can be 4/0 using this.

Agreed if the service to the garage is 200A. Then it doesn't matter if the garage is considered part of the dwelling unit (service qualifies for 310.12, and hence all downstream 200A feeders) or isn't considered part of the dwelling unit (service doesn't qualify for 310.12, but the feeder to the dwelling unit does).

Which was my disagreement with the phrase "if you have a few circuits in the meter main that it doesn't completely fly." As long as all the circuits are part of the dwelling unit, or none of the circuits are part of the dwelling unit, if the service is 200A, then then 200A feeder to the interior panel may use 310.12.

The only problem is if you have a few circuits in the meter main and you judge some of them to be part of the "entire load" of the dwelling unit, but judge others not to be part of that load. Then you never get to use 310.12, as you have no feeder or service that carries just the "entire load" of a dwelling unit.

Cheers, Wayne

 

[LarryFine]

Remember that feeder conductors need not be larger than the service conductors.

 

[Buck Parrish]

Thanks, It's a 200A meter base combo with 60A running to a detached shed. Then I want to run 4/0 AL SER about 25 feet to the main lug panel.

 

[Dennis Alwon]

Firstly, NC is under the 2017 for one & two family dwellings and the 2020 for everything else.

Secondly, 4/0 at 75C is rated 180 amps so it can be on a 200 amp breaker as long as the calculated load isn't greater than 180 amps

 

[Buck Parrish]

Firstly, NC is under the 2017 for one & two family dwellings and the 2020 for everything else.

Secondly, 4/0 at 75C is rated 180 amps so it can be on a 200 amp breaker as long as the calculated load isn't greater than 180 amps

Awesome, thanks. I'll be driving down there tomorrow or Thursday. Maybe I'll see you around.
Thanks

 

[Buck Parrish]

My opinion on why all this was started. It was because so many people were installing a 6 motions of the hand 200A outside panel with no main.
Then feeding a full panel inside on a 90A breaker with #2 SER AL then putting the condenser, the AC, stove and water heater on the outside panel. Dryer on the inside panel. They were maxing out the #2 AL.

Just my opinion.

 

[letgomywago]

Remember that feeder conductors need not be larger than the service conductors.

I can't remember the code reference for this one do you have it for the 2023 in case I ever have it come up.

 

[letgomywago]

Certainly; although then you can't use 310.12 on the service conductors themselves. Plus there is some debate as to whether the service load may be taken to be just the sum of the 220.82 optional load calcs of the two dwelling units.

Agreed if the service to the garage is 200A. Then it doesn't matter if the garage is considered part of the dwelling unit (service qualifies for 310.12, and hence all downstream 200A feeders) or isn't considered part of the dwelling unit (service doesn't qualify for 310.12, but the feeder to the dwelling unit does).

Which was my disagreement with the phrase "if you have a few circuits in the meter main that it doesn't completely fly." As long as all the circuits are part of the dwelling unit, or none of the circuits are part of the dwelling unit, if the service is 200A, then then 200A feeder to the interior panel may use 310.12.

The only problem is if you have a few circuits in the meter main and you judge some of them to be part of the "entire load" of the dwelling unit, but judge others not to be part of that load. Then you never get to use 310.12, as you have no feeder or service that carries just the "entire load" of a dwelling unit.

Cheers, Wayne

Yes I probably should have phrased it better.
Non of the house loads on the meter main but some small detached loads will work and be fine on this rule.

 

[LarryFine]

I can't remember the code reference for this one do you have it for the 2023 in case I ever have it come up.

I don't have a code that new. Is it in 310.15(B)(7)(3)?

 

[Birken Vogt]

I don't have a code that new. Is it in 310.15(B)(7)(3)?

310.12(B)