I Have to hook up a custom made roof unit (make up and exhaust air for kitchen) with 2 motors in the unit. Do I treat this as a motor circuit and calculate the heaters, branch circuits size, overcurrent,feeder size and main breaker? or do I treat this as a piece of equipment and run a branch circuit from the breaker based on the nameplate current?...IE( 40amp breaker #8)
motor or equipment circuit ?
- Thread starter indymark
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electricman2
Senior Member
- Location
- North Carolina
- Occupation
- Retired Electrical Contractor
Re: motor or equipment circuit ?
Some others may have opinions on this but here is my take. Is this equipment listed as an assembly with the motor controls, etc? If so I believe you can supply a branch circuit sized per nameplate data. Otherwise you will need to treat it as two motors and size everything using Article 430.
Some others may have opinions on this but here is my take. Is this equipment listed as an assembly with the motor controls, etc? If so I believe you can supply a branch circuit sized per nameplate data. Otherwise you will need to treat it as two motors and size everything using Article 430.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Re: motor or equipment circuit ?
We trust A/C nameplates without knowing the specifics of the motor encased, right?
I would agree. But I've been wrong before.
We trust A/C nameplates without knowing the specifics of the motor encased, right?
I would agree. But I've been wrong before.
iggy2
Senior Member
- Location
- NEw England
Re: motor or equipment circuit ?
You could probably argue that it is a piece of equipment (appliance) and provide a circuit based on the nameplate. But in reality if you use 125% of the FLA, will the breaker hold? If this is truly a "custom" piece of equipment, is it UL listed, and does the nameplate comply with the NEC? If not, then I would play it safe and treat it as two separate motors, or at the very least a piece of multi-motor equipment. Are there 2 points of connection, or a single terminal box, like on a multi-compressor roof-top unit?
Also, don't they sometimes want to run just exhaust or just makeup air, in which case you might provide separate branch circuits to the motors? Most of the kitchen hoods we design require separate circuits, and they are run off of VFDs for optimal control.
You could probably argue that it is a piece of equipment (appliance) and provide a circuit based on the nameplate. But in reality if you use 125% of the FLA, will the breaker hold? If this is truly a "custom" piece of equipment, is it UL listed, and does the nameplate comply with the NEC? If not, then I would play it safe and treat it as two separate motors, or at the very least a piece of multi-motor equipment. Are there 2 points of connection, or a single terminal box, like on a multi-compressor roof-top unit?
Also, don't they sometimes want to run just exhaust or just makeup air, in which case you might provide separate branch circuits to the motors? Most of the kitchen hoods we design require separate circuits, and they are run off of VFDs for optimal control.
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