# #12 AWG on 25 amp OPD



## Voltech (Nov 30, 2009)

I cant remember the reason I was able to use a 25 amp OCPD with #12 on a motor. I think it was because of the start up amps it pulled that made it use a 25 amp.

Any help? My boss told me today " There are no circumstances where #12 should be on any OCPD larger than 20 amps"

Would love to get a free lunch.


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## NolaTigaBait (Oct 19, 2008)

Yeah, for a motor you can size ocp at 250% of the flc.


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## MDShunk (Jan 7, 2007)

Voltech said:


> I cant remember the reason I was able to use a 25 amp OPD with #12 on a motor. I think it was because of the start up amps it pulled that made it use a 25 amp.
> 
> Any help? My boss told me today " There are no circumstances where #12 should be on any OPD larger than 20 amps"
> 
> Would love to get a free lunch.


Air conditioning equipment and motor loads are two instances where he is wrong.


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## Magnettica (Jan 23, 2007)

Tell your boss you would like a free lunch. 

A/C branch circuits can be #12 THHN with 40 amp OCPD if the nameplate data says so.


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## MDShunk (Jan 7, 2007)

I should say, however, that if that #12 terminates at a receptacle outlet, your boss is right. If it goes to (certain) equipment directly, then he is wrong in certain cases.


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## sparks134 (Jan 30, 2009)

Tell your boss to look at table 240.4 G... Tell your boss buy you want 

steak for lunch!!!


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## Dennis Alwon (May 9, 2009)

Table 310.16 shows that #12 wire is good for 25 amps at 75C. Thus using article 240.4(D & G) by the asterisk at the bottom of the table, we are not only allowed to use #12 with a 25 amp breaker but we can use #12 at 25 amps and use a 45 amp breaker.


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## Voltech (Nov 30, 2009)

sparks134 said:


> Tell your boss to look at table 240.4 G... Tell your boss buy you want
> 
> 
> 
> steak for lunch!!!


I wont hit him up for a steak, but I wont settle for fast food:thumbsup:

He has an open policy in the shop. Prove him wrong and he will buy you lunch. Its a win win situation for him IMO


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## JohnR (Apr 12, 2010)

Voltech said:


> I wont hit him up for a steak, but I wont settle for fast food:thumbsup:
> 
> He has an open policy in the shop. Prove him wrong and he will buy you lunch. Its a win win situation for him IMO



Sounds like a pretty good boss to me. He hiring?


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## Roger (Jul 7, 2007)

Here is an example of a #12 on a 45 amp breaker.

A branch circuit to a 3 HP 230 V single phase motor; all parts are listed for 75 deg C. 

(Hint; articles 240.6, 310.16, 430.22(A), tables 430.52, and 430.148)


Table 430.148 gives a 3HP motor a full load current of 17 amps
430.22(A) requires conductors be sized at 125% of full load current 
17 x 125% = 21.25 amps
 Table 310.16, #12 THHN 75 deg C column = 25 amps
 Table 430.52 allows up to 250% for the inverse time breaker
 17 x 250% = 42.5 amps 
 240.4 states we can go UP to the next STANDARD size breaker
 240.6 would let us go up to a 45 amp breaker
 *Answer 45 amp breaker. *
Roger


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## Dennis Alwon (May 9, 2009)

Very nice Roger. I almost posted something similar along with my post above but I was too slack.


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## Greg (Aug 1, 2007)

The reason why you can a breaker larger than 20 on a 12 wire is because a motor circuit is the best protected circuit out there. You have overloads protecting the motor should the motor go into a fault condition, the O.L.'s will release before the breaker trips. This because of how they are sized according to code.


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## Voltech (Nov 30, 2009)

This Back fired on me today...Went to the seafood buffet got stuffed..Then got sent out to lay out a slab. I was not worth a ***.. I sounded like my 5 year old.."my belly hurts"


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