How to size the circuit that activates a lighting contactor's coils?

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Calrissian45

Calrissian45

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Southern California
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Electrical Engineer
I need to install a lighting contactor for a single phase, 240V, 30A lighting circuit so I can control the lights with 120V, 20A three-way and four-way switches. I can't find any information on the contactor data sheets on how to size the conductors for the control module though. Maybe I'm just overlooking it since it's Friday afternoon, but I was hoping someone could point me in the right direction.
 
Just to suit the breaker supplying the control circuit. In most cases, that wold be #12.

A contactor that small uses very little coil current.
 
An AC contactor has two ratings. It has an initial pull in surge then a much lower holding current. Most often though instead of actual numbers you will see a “VA” rating for the surge for sizing the transformer if it’s control power transformer fed. But 95% of the time the ratings are in the data sheets that you have to hunt for. One of the issues is private branding. You might not recognize the names Sprecher and Schuh (Polish plant) or LSIS (Spanish plant) but you will recognize AB, Schneider, GE, Siemens, and others. What do they have in common? The first two actually make the contactors, then screen print the names in the second list. It’s all private branded. So as end user you get to try to find the actual specs.

That being said the big issue is making sure the power supply (fuses, transformer) is big enough. Even with #16, ampacity has never been an issue even with large NEMA size 6+ contactors.
 
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