Band saw motor circuit

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Jacob S

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Location
Georgia
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Electrician
Hello all,
I have a situation where i need to wire a bandsaw. First off, motor circuits are a weak area for me since I do not do them often, so assistance is greatly appreciated. The band saw has a 2 horsepower cord and plug connected motor. So, here is what I was thinking of doing:
* Table 430.248 gives a 2HP motor an full load current of 12 amps at 240 volts
* 430.22(A) says the conductors need to be 125% full-load current, so that's 16 amps
* Table 310.16, #12 romex 60 deg C column = 25 amps
* Table 430.52 allows up to 250% for the inverse time breaker, so that's 40 amps

Now, i understand sizing breakers larger than conductors for air conditioners and the such, but how do i can around 210.21 (B)(1)? The saw has a L6-20 twistlock on it.

Should i run # 12 from a 40 amp breaker to a fused disconnect with 20 amp time delay fuses in it?
Thanks for all your input!
Jacob
 
They installed a 20 amp straight blade plug, according to the manual (forget the nema configuration). Currently, the way I found it, it is a l6-20 twistlock.
 
Jacob S said:
They installed a 20 amp straight blade plug, according to the manual (forget the nema configuration). Currently, the way I found it, it is a l6-20 twistlock.
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Than it is not possible to connect it to a larger overcurrent device.

I recommend consulting the saw manufacturer about this.

Or I might a new breaker on the possibility the breaker is out of whack.
 
Well, that was i was kind of thinking. Is it permissable to install a 30 amp breaker with # 10 conductors to a fused disconnect with 20 amp time delay fuses?
 
Today, I went back out to the saw to check out the situation a little more. Here is what is troubling me and would love some insight on. How do I connect a 2 HP 240V motor using a cord? Today, i put my fluke 334 amp probe on it and used its inrush feature to measure the peak amp draw. It came to 69 amps per leg. It is more between 40 and 60 during start up, but does peak at 69 amps. No wonder the 20 amp breaker trips during startup. For trouble shooting, I did install what would be a permissible over current device for that particular motor (40 amp). Obviously, the tool consistently started without a problem.

So, how would you handle this issue?
Is there an exception somewhere that would allow a breaker sized larger than the outlets rating, just for motors, to get around 210.21 (B)(1)? Maybe time delay fuses? I really have never had to deal with motors this large that are cord and plug connected before. If it were hardwired, it would be easy.
Thank you for your help.
Jacob
 
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how far away is the saw from the panel? had a similar problem with a paint mixer tripping a breaker. checked the voltage with the motor running and saw 90v on a 120 circuit.
 
dcl34769, Thank you very much for your response. I checked voltage on startup and it stays 230v or above at the machine. Do you think the motor starting capacitor might be on the fritz?
 
Since it's a motor circuit we're dealing with, a 30A breaker is OK on #12 if you have overload protection. Look in Art 430 for this application.

That 20A breaker, or any 20A breaker will likely trip on inrush which is why the NEC allows larger breakers for motors. Does the saw have integral OL protection?
 
Thanks for your replies,
Well, I should have done what IWIRE suggested from the start to consult the manufacture. I did this morning, and they believe it is an issue with the motor. They are going to have one of their techs in the area look at it and make any necessary repairs. Thanks again
Jacob
 
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