30 A contactor on 40A circuit

[steve66]

Can you put a 30A lighting contactor on a 40A circuit if the load is less than 30 amps? This is for an outdoor lighting circuit.

Steve

 

[steve66]

The load on the circuit is 27 amps, and since it is a lighting load, it is continuous, if that makes a difference.

 

[nakulak]

1.25 x 27 = 33.75 amps. Seems to me the required rating of the contactor should be at least 33.75 ? (sorry I don't know the code section)

 

[Jraef]

The contactor will have data saying it must be protected by an OCPD not greater than its maximum rating. So from that standpoint, you are using it in a manner beyond its intended use. Change the breaker to 30A or change the contactor to 40A.

 

[davidaengelhart]

1.25 x 27 = 33.75 amps. Seems to me the required rating of the contactor should be at least 33.75 ? (sorry I don't know the code section)

May I suggest 110.3(B)?

 

[stew]

seems to me that the breaker probably would hold at 33.75 amps anyway. A breaker change is not the solution in my opinion you are still overloading a 30 amp device or devices both the breaker and the contactor. get a contactor rated 40 amps or higher for the correct solution or maybe you can shift some loads to get what you need and not overload this system.

 

[steve66]

Thanks for the replies. I'm just reviewing a set of drawings for code compliance, so the 30A contactor on a 40A breaker was another designers idea.

I just wanted to make sure it was really an issue before I told the designer he had to revise the design.

I think your all right that 110.3 B and the instructions are about as close as I'm going to get.