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100A subpanel - Printable Version

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RE: 100A subpanel - TDKPE - 04-25-2021

On further review, it looks like you can use SER for branch circuits and feeders at its 75C ampacity as long as it’s not covered in thermal insulation, in which case you have to either de-rate it from it’s insulation class ampacity (which may be 90C) as long as it’s not greater than the 60C ampacity, or just use the 60C ampacity.

If that’s the case, then the OP doesn’t have an issue as long as it’s not buried in thermal insulation.  I’ll check tomorrow when I have access to the current NEC.  

I haven’t been keeping up.  Too much (future) retirement thinking creeping in these days.   Crazy


RE: 100A subpanel - srv52761 - 04-25-2021

(04-25-2021, 09:31 AM)but TDKPE Wrote: On further review, it looks like you can use SER for branch circuits and feeders at its 75C ampacity as long as it’s not covered in thermal insulation, in which case you have to either de-rate it from it’s insulation class ampacity (which may be 90C) as long as it’s not greater than the 60C ampacity, or just use the 60C ampacity.

If that’s the case, then the OP doesn’t have an issue as long as it’s not buried in thermal insulation.  I’ll check tomorrow when I have access to the current NEC.  

I haven’t been keeping up.  Too much (future) retirement thinking creeping in these days.   Crazy

I was hoping you would chime in.  
It is hard to keep up.  when I submitted my plans and got my permit we were under the 2014 cycle.  
Covid hit and city hall shut down.  I couldn’t get my trench or rough in inspected. 
Winter set in and I am too old to work in sub freezing temperatures. 
Then a fire at the Square D plant in Mexico, my 90 amp breaker was back ordered.  Supplier told me he would put a rush on it, but he also told me realistically everyone is short and priority is for the bigger commercial jobs.  Months later it still wasn’t here. 
 In the mean time our city moved to the 2017 cycle.   March the city called, there is a 1 year time period on the permits.  The inspector knew it had been a year trying to get a simple sub panel and shed wiring job approved.
He told me to go ahead and put a 100 amp breaker in and he would pass it.

April, the state of Iowa adopted the 2020 code.  Things are changing too fast.


RE: 100A subpanel - JosephP - 04-29-2021

SER 2-2-2-4 was $1.20/ft at local supplier.  I started pulling that this afternoon along the long wall, but ran out of time for now.  Builder brought his scissor lift back for me to use for the weekend.  Wouldn't have wanted to wrestle that wire without it!


RE: 100A subpanel - srv52761 - 04-30-2021

(04-29-2021, 08:11 PM)JosephP Wrote: SER 2-2-2-4 was $1.20/ft at local supplier.  I started pulling that this afternoon along the long wall, but ran out of time for now.  Builder brought his scissor lift back for me to use for the weekend.  Wouldn't have wanted to wrestle that wire without it!

Make sure to use a lot of Noalox at every connection.


RE: 100A subpanel - Mr_Mike - 05-03-2021

I've been looking for a 90 amp Homeline breaker now for months. Looks like my Lowes finally has one I can order. It is supposed to be here in a week. Hope it works. Right now, I just have a 60 amp feeding my Spa panel. I'll swap out the 60 when it arrives. If it arrives.


RE: 100A subpanel - srv52761 - 05-03-2021

(05-03-2021, 11:55 AM)Mr_Mike Wrote: I've been looking for a 90 amp Homeline breaker now for months.  Looks like my Lowes finally has one I can order.  It is supposed to be here in a week.  Hope it works.  Right now, I just have a 60 amp feeding my Spa panel.  I'll swap out the 60 when it arrives.  If it arrives.

Yeah, I was 3 months in when my permit was about to expire.  My AHJ felt bad for me.  Passed me with a 100 amp.

Those 90 amp ones are a special order.  They were put on the back burner (pun intended) when the plant in Mexico caught fire.
90 amps... 100 amps.  Looks good on code, but in real life, probably not a big deal.


RE: 100A subpanel - Mr_Mike - 05-03-2021

90 exceeds my need and there will be no safety issues. I do need to get back in the attic and elevate the last 20 ft of cable off the insulation though.