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100 Amp Sub-Panel with 2/0 gauge - lucky/unlucky day?

M

Mellotron

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Wow I think the combination of lack of coffee and the time change has somewhat worked in my favor today at Lowes. I sleepily asked an equally sleepy Lowes associate for 2 guage copper THHN for my 100 amp sub-panel feed and he whips me up a roll of 2/0 instead! I didn't really make the connection until I got home and had my coffee.

I'm hoping the 2/0 does not give me any grief going into breaker lugs, etc. Totally overkill for 100 amp sub at 6 feet away but hell, Lowes is 35 miles away.

I suppose it's not really my lucky day since now I have hump around 2/0 in conduit, etc. Ah well. Just thought I'd share my sleepy moment with you all.
 
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mrb

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the 2/0 might not work in some of the lugs you need it to. For example a 100 amp breaker feeding your subpanel. Maybe see what you can get from a scrap yard for the 2/0 and buy #2 and lunch with the proceeds.
 
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Stuart in MN

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Did they charge you for #2 or #2/0?

It will depend on the brand and model of your panel and the breakers, but I just looked in the Square D catalog and the lugs in a 100 amp QO panel have a maximum capacity of #1 copper.
 
OP
M

Mellotron

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Stuart in MN said:
Did they charge you for #2 or #2/0?

It will depend on the brand and model of your panel and the breakers, but I just looked in the Square D catalog and the lugs in a 100 amp QO panel have a maximum capacity of #1 copper.
Click to expand...

Sigh.... They charged me for 2/0 :sad:
I got all GE equipment, I think the Neutral and Ground lug I installed will be ok, I'll have to check the new 100 amp breaker and see. Crossing Fingers.
 
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MrMark

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You will have one hell of a time bending that 2/0 into a breaker. Forget it. You would need a special bender to make that 90 turn, it's not worth it. Number 2 is hard enough to work with.
 
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walrus

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I think you'll find 1/0 is as big as a common GE(THQB?) breaker will take
 
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BioHazard

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I literally have three different brands of 100A breaker in front of me - Siemens, Sq D QO and Homeline, and CH - all of them say 2/0 for the max wire size.

Doesn't mean it will be easy...but it should fit.
 
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Norcal

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If 2/0 is used the grounding conductor if used, needs to be upsized also. See 250.122(B)
 
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MrMark

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Actually #3 is required if in conduit, #2 if romex. This is a subpanel, you are thinking service entrance where 4 is good for 100 amps.

The OP will have no success with landing the 2/0 on a breaker even if the breaker accepts the wire. He will never manage to get it bent and cleanly into the breaker so as to not strain the breaker with respect to the bus bar.

2/0 is for a 200 amp service entrance..
 
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N

Norcal

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MrMark said:
Actually #3 is required if in conduit, #2 if romex. This is a subpanel, you are thinking service entrance where 4 is good for 100 amps.

The OP will have no success with landing the 2/0 on a breaker even if the breaker accepts the wire. He will never manage to get it bent and cleanly into the breaker so as to not strain the breaker with respect to the bus bar.

2/0 is for a 200 amp service entrance..
Click to expand...

2/0 is for a residential service. 3/0 copper is the normal size because the NEC allows smaller conductors for a residential service entrance.
 
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nate379

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Yeah your right, was thinking service panel. Why the need to upsize for a sub panel??

I run #10 from my main to a sub panel for 30 amp service (just a shed with some lights/outlets and my air compressor).. is that not correct?
 
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MrMark

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Well, the subpanel is actually the normal size ampacity as Norcal has pointed out above. The NEC allows slightly higher ampacities for residential service entrances based on anticipated load diversity, I would imagine.

Yeah, you are right on the feed if that is sufficient for your shed. You have the right wire and breaker.
 
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JBurgess

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MrMark said:
Actually #3 is required if in conduit, #2 if romex. 2/0 is for a 200 amp service entrance..
Click to expand...

#2 romex would only be good for 95 amps. If protected with a 100 amp breaker be prepared to show load calcs that load is 95 amps or less.
 
OP
M

Mellotron

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Yeah several of you nailed it. This wire is so thick that it was a struggle just to bend it out to strip off a bit in attempt to see if I could shove it in the breaker. No such luck there.

Looks like THQL series have smaller lugs than other brands. Rightfully so. Really makes no sense to accomodate a giant gauge wire where on the other end of the breaker is two measly little stabs with less combined surface area than a 4 gauge wire......

Well back to Lowes for some 2 or 3 gauge! But Coffee first this time!!!!

Thanks for the replies!
 
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