motor help

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normbac

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went on a service call for a complaint of burnt smell, I opened the j box and a wire was lightly overheated it is a 7.5 hp motor for a compressor 208 1ph wire size are #10 no disco I am not clear if this is compliant it is within sight 20 ft. from panel but I thought it needed fused disco anyway? also wire size #10 seems to small for this motor nameplate states 31amp at 208 I dont want to criticize installation and be wrong but this seems incorrect TIA
 
Is this an air conditioning compressor or just an air compressor. The rules are not exactly the same, but it is likely that the installation is code compliant, but more information is needed to be sure. Where is the motor controller? Does it have an overload relay or other overload protective device? What is the rating of the breaker?
 
don_resqcapt19 said:
Is this an air conditioning compressor or just an air compressor. The rules are not exactly the same, but it is likely that the installation is code compliant, but more information is needed to be sure. Where is the motor controller? Does it have an overload relay or other overload protective device? What is the rating of the breaker?
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Air compressor 40a cb specs dont show a overload relay motor controller is mounted on air compressor Thanks
 
430.22(a): conductors need to be sized at 125% of full load current. 430.6(a)(1) exception 3: Calling it a appliance. I came up with 39amps, #8 copper.

430.39: Can use motor controller as overload protection. I'm assuming it has heaters or fuses or something inside that trip if a overload occurs. If not then you need overload protection, 430.32(a)

430.102: I'm thinking you could use the breaker as the disconnecting means if it was lockable in the off position.

I'm not overly experienced with motors but this is what it looks like to me.
 
The motor may have an internal thermal device to turn the motor off in the event it gets too hot. Many single phase motors have these such as garbage disposers, washing machine motors, dryer motors, most home workshop motors ( table saw, drill press). These are used instead of a separate motor overload.
 
This installation is covered by Article 430. If the breaker is within sight, there is no code requirement that it be lockable. Yes, you are required by the OSHA rules to lock it out if you are working on it, but the NEC does not require that the installer provide the means of locking the breaker out.
 
don_resqcapt19 said:
This installation is covered by Article 430. If the breaker is within sight, there is no code requirement that it be lockable. Yes, you are required by the OSHA rules to lock it out if you are working on it, but the NEC does not require that the installer provide the means of locking the breaker out.
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So, just prop your helper against the panel door and you're okay. :cool:
 
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