argument with electrician

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mmm_max

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Trying to resolve an argument with my electrician. He says I need awg 1 for service to a 100 amp subpanel. I am saying that i need only # 4 for the two hot feeds to the breakers because the breakers should be balanced in amperage for each hot. 50 amps each side but the return will have to take the full 100 amps from both hots. Am I wrong. Distance is around 80 feet from the feed.
 
You are wrong. The full 100 amps must be able to be accommodated by each line and each line conductor.
 
mmm_max said:
Trying to resolve an argument with my electrician. He says I need awg 1 for service to a 100 amp subpanel. I am saying that i need only # 4 for the two hot feeds to the breakers because the breakers should be balanced in amperage for each hot. 50 amps each side but the return will have to take the full 100 amps from both hots. Am I wrong. Distance is around 80 feet from the feed.
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Seriously, you hire an electrician and you obviously have no faith in him/her and then you want to correct them. LOL you sound like me..... What you stated is not uncommon to hear from people who have not been in the trade.
 
Dennis, Are there electrician and then there are folks that say they are electricians? I like to check the numbers. I do my own wiring but only on three phase motors and the only panels that I have burned up have been because I failed to re-torque the damn aluminum wire lugs! Now I have a temperture meter and retorque every season. I learn some.
 
mmm_max said:
Trying to resolve an argument with my electrician. He says I need awg 1 for service to a 100 amp subpanel. I am saying that i need only # 4 for the two hot feeds to the breakers because the breakers should be balanced in amperage for each hot. 50 amps each side but the return will have to take the full 100 amps from both hots. Am I wrong. Distance is around 80 feet from the feed.
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If anything, the neutral is the one that could possibly be smaller. (Although usually in a 100A residential feeder they are all the same size.) Current in the two hots goes in the opposite direction to the neutral at any given instant so it cancels out in the neutral instead of adding. You have a lot to learn before questioning your electrician, even if he has the required wire size wrong.
 
Can't second guess the electrician there, I'd say he's right based on table 310.15(B)(16) and a best case scenario.
#4 even if copper will not give you 100A even under best circumstances for a subpanel feeder.
Minimum of #2 Aluminium best of circumstances and most likely #1 Al would be needed for 100Amp subpanel feeder. Many things can present to require a larger conductor than even these tables might indicate and the electrician installing should be best qualified to determine all factors and come up with the correct wire size.
Beyond this, any qualifying answer would be only a guess and a disservice to you.
If you're not happy with your electrician sizing, approach your AHJ for a second opinion and a review of your installation.
 
If I had a customer that so thoroughly misunderstood electrical, don't know how to start explanation

And when he told me what size wire to use based on his misunderstanding, maybe I could stay calm and polite, but not likely based on previous experiences

Good case could be made that I shouldn't be posting on this thread but keep feeling the need to slip it in before locked, surprised that it hasn't already
 
readydave8 said:
If I had a customer that so thoroughly misunderstood electrical, don't know how to start explanation

And when he told me what size wire to use based on his misunderstanding, maybe I could stay calm and polite, but not likely based on previous experiences

Good case could be made that I shouldn't be posting on this thread but keep feeling the need to slip it in before locked, surprised that it hasn't already
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I'm finishing up jobs for 2 builders this month, then shedding them off my books, partly for that reason.
 
readydave8 said:
Good case could be made that I shouldn't be posting on this thread but keep feeling the need to slip it in before locked, surprised that it hasn't already
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No reason to lock this thread and actually it would be nice if the OP came back and clarified the wiring method and the conductor material that they're using. For conduit and wire: all three sizes of copper are code compliant but only #1 aluminum would be code compliant. For copper NM cable #2 with next size up rule or #1 are code compliant.

Here's some possibilities from T310.15(B)(16):
Conduit and wire @75° C:
Copper:
#3=100 amps
#2=115 amps
#1=130 amps
Aluminum:
#3=75 amps
#2=90 amps
#1=100 amps

NM cable @60° C:
Copper:
#3=85 amps
#2=95 amps
#1=110 amps
 
Another C10 said:
If they are Licensed, don't argue with them. Chances are they went to school and read the code book. .. just saying ..
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I get where the op is coming from because there are a lot of uneducated workers out there. First is, of course, is this the licensed guy who said that or one of his workers. I have seen cases where the homeowner was correct and the electrician incorrect but normally that is not the case.

Some people hate someone hanging over them but I don't mind as long as they don't slow me down too much.
 
What about engineers? I suppose everything said is certainly true for short runs but what about voltage drop? It sound like we are talking about 240VAC single phase maybe 208VAC service. The length of wire, power factor, type of load if a motor, some lighting loads, heaters or other special equipment can affect wire sizing. I have my issues with voltage drop calculations because the numbers are affected by so many different values such as temperature, resistance, reactance, load type, power factor and the like that it is impossible to calculate voltage drop with any accuracy but it is required by the energy code not NEC.
 
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