Condenser Question

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I am constantly having to "educate" those HVAC guys about the allowances of 240.4(G).

We wired a unit that has a minimum of 15 Amps, and Max of 30, and they wanted me to use a #10 for it. They say "everybody knows you have to use a #10 on a 30 Amp breaker" or some such nonsense. :roll:

I ended up using a #12 (since that was what I had on the truck) on a 30 amp breaker and they had a fit.

After some explaining about the Code allowances I challenged them to start up the unit, and put their amprobe on the lines and then tell me it was overloading the #12.

You just can't teach some old dogs new tricks sometimes. :mad:
 
not looking at a code book now, but from memory I thought 12 was only good for 20 amps in most situations,tables are only used for derating for 3 or more conductors in raceway.also romex uses 60 degree
 
sparkfree said:
not looking at a code book now, but from memory I thought 12 was only good for 20 amps in most situations,tables are only used for derating for 3 or more conductors in raceway.also romex uses 60 degree
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Did you read this thread? ;)
 
stickboy1375 said:
I would bet 1/3 of electricians do not know about 240.4(D).
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russ said:
More like 99%

The few that participate here not included.
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sparkfree said:
not looking at a code book now, but from memory I thought 12 was only good for 20 amps in most situations,tables are only used for derating for 3 or more conductors in raceway.also romex uses 60 degree
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More like 99.1 %???
 
sparkfree said:
not looking at a code book now, but from memory I thought 12 was only good for 20 amps in most situations,tables are only used for derating for 3 or more conductors in raceway.also romex uses 60 degree
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#12 THHN is a 90 degree conductor and is good for 30 amps according to 310.16. There are restrictions based on other code articles for the use of #12 THHN at 30 amps. One would be 240.4(D) which limits it ampacity to 20 amps except under certain circumstances like motor circuits and HVAC circuits. Even at 60 degrees #12 is still good for 25 amps.
 
sparkfree said:
. . . I thought 12 was only good for 20 amps in most situations . . .
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It's not that it's only "good" for 20a, just that for "most situations" the code limits OCP to 20a. HVAC is one of the other situations.
 
Sparkfree's comment that NM cable (Romex) is limited to a 60 degree conductor rating based on 334.80 (NEC 2005). Don't make a difference on smaller conductor sizes but will effect larger conductor sizes.
 
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