Feeder from OCD to combination starter

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masterelect1

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A contractor had the job of installing in a car wash a rooftop exhaust fan - 480 - 3 ph, 3HP. There was a spare 100 ampere 3ph circ. Brkr. in the dist panel which he used to feed his combination starter. He ran 3/4" RMC and #12 wire to feed the combo starter. The combo starter is properly sized with OL heaters, supply side fuses, control xfmr. fuses, etc...

I have told him that the #12 is undersized and that if he wishes to use that 100 amp CB he needs to pull in the proper size conductors (#2) (and increase conduit size) that could handle the load up to the rating of the OCD.

I am tired of reading Art. 430.

Where can I point to justify my opinion.

Thanks, John
 
First, #12 wire isn't undersized. It's more that the 100A CB is oversized :grin:

At this point it may be more cost effective to replace the circuit breaker...
 
Smart $ said:
First, #12 wire isn't undersized. It's more that the 100A CB is oversized :grin:

At this point it may be more cost effective to replace the circuit breaker...
Click to expand...

The #12 is undersized when a complete installation by the EC is done and he calls for an inspection. He has every right to re-use the 100 amp cb if thats his intent, he simply has to install the right size feeder conductors.

As for cost effectiveness, thats why he used the existing breaker and abandoned conduit.
 
3hp - 3 ph - 460 vac - 15a brkr - size 0 - 5.52 heater - 12 awg - 3/4 conduit..............from ugly's '08

branch cir conductor 430.250
branch cir OCPD 430.52(C1)
Feeder 430.24
Feeder OCPD 430.62(A)

or what don said IMHO
 
don_resqcapt19 said:
How long are the #12s? If 10' or less, then 240.21(B)(1) would permit the installation.
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75-80'

This EC just wanted to get in and out and use what was there, that is cb and conduit. This should have been a simple install and has become a nuisance due to his lack of knowledge and ego.

Simply put, a 75' run from a 100 amp cb (because thats what he used, not what I would have done) has to have the right size conductors - I'm looking for back up in the code without all the exceptions in 430, which is what he keeps referring to.
 
Article 430 IS what applies here. First look at 210.1 which refers you to 430, then look at table 430.52, chances are the existing 100 amp breaker is a thermal magnetic type (or non adjustable) and therefore could only be sized to a maximum of 250 percent larger than the FLA of the 3 HP motor (4.8 amps). Using the next largest standard breaker, this would equal a 15 amp breaker. Unless this is an industrial situation where there is unlimited tap conductor length, IMHO the breaker does not meet code and is oversized (not to mention really poor design).
 
masterelect1 said:
75-80'

This EC just wanted to get in and out and use what was there, that is cb and conduit. This should have been a simple install and has become a nuisance due to his lack of knowledge and ego.

Simply put, a 75' run from a 100 amp cb (because thats what he used, not what I would have done) has to have the right size conductors - I'm looking for back up in the code without all the exceptions in 430, which is what he keeps referring to.
Click to expand...

Try 210.20 and 240.4
 
If it's a properly sized combination starter, Art 430 should be satisfied.
At best you could rely on 240.21, but it would not appear any of these would qualify with the length and wire size you are describing.
 
masterelect1 said:
The #12 is undersized when a complete installation by the EC is done and he calls for an inspection. He has every right to re-use the 100 amp cb if thats his intent, he simply has to install the right size feeder conductors.

As for cost effectiveness, thats why he used the existing breaker and abandoned conduit.
Click to expand...
Yes he could install properly sized conductors for the 100A CB, if you want to be adamant on your point of view.

However the real life question is what is the safest and least costly fix to the current situation. Hmmm... buy 80' of at least 1-1/4" RMC, 250 feet of #2 (or possibly #3) Cu, install and connect... versus ...(1) 3P breaker and replacement of existing. So if it was your money, which would you do?
 
Smart $ said:
Yes he could install properly sized conductors for the 100A CB, if you want to be adamant on your point of view.

However the real life question is what is the safest and least costly fix to the current situation. Hmmm... buy 80' of at least 1-1/4" RMC, 250 feet of #2 (or possibly #3) Cu, install and connect... versus ...(1) 3P breaker and replacement of existing. So if it was your money, which would you do?
Click to expand...

No offense but I know what I would do. I was simply looking for a definitive code reference to tell this guy to FIX IT.

Thanx all for the input- situation has been resolved.
 
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