10 AWG and 40A square D breaker

10 AWG and 40A square D breaker

  • Ignore the restriction and put the 10 on the breaker

    Votes: 10 40.0%

  • Use a wire nut to splice and 8 onto the 10 in the panel

    Votes: 6 24.0%

  • Some other splice method for an 8 (explain what)

    Votes: 2 8.0%

  • Some other method (explain it)

    Votes: 7 28.0%
  • Total voters
    25
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paul32

Senior Member
Location
Minnesota
I would think this is relatively common to have an air conditioner with max breaker of 35 or 40A and the MCA under 30A, which would only need 10AWG wire. The square D breakers 35A and up aren't rated for wire smaller than 8AWG. So what do you do?
 
I would use the correct wire size for the breaker. 30 amp gets #10 for the complete run. 35 amp gets #8.
 
I'll probably get hammered...but...

I don't use Square D.

I would never connect #10 wire to a breaker whose lugs were rated for #8 minimum.:rolleyes:
It wouldn't matter if the conductors were nice and tight either.

By the way...Are you talking about QO or Homeline?

steve
 
paul32 said:
I would think this is relatively common to have an air conditioner with max breaker of 35 or 40A and the MCA under 30A, which would only need 10AWG wire. The square D breakers 35A and up aren't rated for wire smaller than 8AWG. So what do you do?
Click to expand...


Pigtail the breaker with # 8....
 
That is interesting...the 35 to 70 amp breakers have a #8 minimum wire size, but the 80 to 125 amp ones have a minimum wire size of #12!
Don
 
John Valdes said:
I would use the correct wire size for the breaker. 30 amp gets #10 for the complete run. 35 amp gets #8.
Click to expand...

The 10 AWG with a 35 or 40 breaker is correct in this application. The only problem is this particular breakers terminal can not accept a 10 AWG.

I would probably pigtail some 8 AWG onto the 10 AWG.
 
WTF?


SquareDterminationsQO.jpg



On Page 6/40 over here:
http://ecatalog.squared.com/pubs/Circuit%20Protection/Miniature%20Circuit%20Breakers/QO-QOB%20Circuit%20Breakers/QO-AFI/0730CT9801.pdf

More here:
http://ecatalog.squared.com/catalog/apo/index.cfm?page_id=1&funct=additems&Ref=QO235&Qte=20&Class=&numitems=1


I searched, but haven't found an answer...
 
If the MCA was under 30 amps I would use a 30 amp CB with the #10 conductors.
 
I have never thought about the minimum size for the breaker. I don't use Sq. D but I always have put 10 gauge under a 40 for an A/C unit. I have never had a problem but if it fits and is snug- I don't see the problem. I will have to check GE when I get a chance.
 
I use the correct wire size for the breaker. I size #10 with 30amp breaker. When I was a industial electrician, we told to always protect the machinery. So we never fuse higher than what the motor called for and never use smaller wire.
 
guschash said:
I use the correct wire size for the breaker. I size #10 with 30amp breaker. When I was a industial electrician, we told to always protect the machinery. So we never fuse higher than what the motor called for and never use smaller wire.
Click to expand...


The motor overloads protect the wire... and in some circumstances I dont see how you could have overcome startup current with a standard size breaker...
 
Last edited:
guschash said:
I use the correct wire size for the breaker. I size #10 with 30amp breaker.
Click to expand...

There are many 'correct' size wires for 30 amp breakers.

There are times that it is perfectly acceptable to use 14 AWG with a 30 amp breaker.
 
iwire said:
There are many 'correct' size wires for 30 amp breakers.

There are times that it is perfectly acceptable to use 14 AWG with a 30 amp breaker.
Click to expand...

Agreed....example look at name plate ratings on HVACR equipment. Based on a balance between LRA, RLA, etc.
 
I just went down the basement and pulled out a dp 40 GE and an old Sq. D DP 40. The GE does not mention wire size but the SQ. D does )#8-4. I needed reading glass as well as a magnifier to read the darn thing.

Anyway I put a 14 wire under the sq.D 40 and I gotta say there is no way in the world that connection would come loose. I whirled the breaker around by the wire and it was still "snug as a bug in a rug". So why is it listed for #8-4???

I guess I would have no problem defying that listing. Sorry-- kill me-- go ahead.
 
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