Multimotors on a starter

Article 430 of the NEC deals with motor circuits and controllers. Read it. It isn't very long. You should contact the Building & Safety department of your city or county and ask which edition of the NEC they follow. Read that edition to see if it forbids this arrangement. If both controllers meet all the other requirements, viz. capacity, proper grounding, etc. this setup shouldn't be disallowed.

Of course, if this installation will be subject to some sort of inspection, or if you suspect there is reason for concern with the other wiring, read the rest. The NEC exists to protect life and property, and many (not all) of the requirements are just common sense. Better to correct an out-of-code situation before it becomes a problem.

Excellent answer. I'll just add that it is not uncommon in the HVAC industry to see OEMs use cost cutting methods and components that would be considered "questionable" engineering practice but which are technically legal. A case in point is that you will also frequently see them use 2 pole contactors to switch 3 phase loads. Bad form, but not illegal.

Dependant upon 3 phase type.

Would work on Wye but not on Delta connection........two pole contactor definately illegal on Delta.

MR. GUY

Thank you for your input.

sounds like both contactors disconnect power on each leg of the single phase motors,

where is the hazard or problem,? most home 220 volt air conditioners use a single pole

contactor perry

Sounds like you are dealing with equipment supplied from a manufacturer (compared to something built on site). If this equipment is independently evaluated by a testing organization and listed by them, such as Underwriters Laboratories (UL), then the National Electrical Code normally accepts them as an approved factory assembly. The code requirement then is to apply and install them in accordance with any factory instructions and any limits from the listing.

Many times, the condenser fan motors will have their own internal overload protection, so there is no need for providing this within the motor controller. Since these are single-phase motors, the situation you describe appears to be OK. I assume that the contactors are rated for an inductive load, and sized to carry the motor nameplate amps. Just make sure that any replacement items are capable of doing the same job that the originals did.

--JMM

Thank you all for your input