using a lighting contactor to switch a transformer

[rmitts]

I am curious if there is a particular code reference that allows or disallows a contactor to control a transformer that feeds a lighting panel,
the 480v feed comes from the mcc to the lighting contactor( that is controlled by a photo eye) then to the 30kva transformer primary side, secondary to the lighting panel. contactor is in an unclassified area and the panel and transformer are located in a class1 division2 group D area

 

[GoldDigger]

I am curious if there is a particular code reference that allows or disallows a contactor to control a transformer that feeds a lighting panel,
the 480v feed comes from the mcc to the lighting contactor( that is controlled by a photo eye) then to the 30kva transformer primary side, secondary to the lighting panel. contactor is in an unclassified area and the panel and transformer are located in a class1 division2 group D area

I think that the question to be asked is whether the lighting contactor can handle the inrush turn on current of the transformer and whether it can handle the possible inductive kick when opening again.
Other than requiring the contactor to be used within its manufacturer rating I do not think that the code addresses the issue.

 

[rmitts]

I think that the question to be asked is whether the lighting contactor can handle the inrush turn on current of the transformer and whether it can handle the possible inductive kick when opening again.
Other than requiring the contactor to be used within its manufacturer rating I do not think that the code addresses the issue.

its a 200amp contactor, so it is large enough, I could not find a code reference one way or the other on the installation just thought it might be tucked away in a less than obvious location, the general consensus here is that it just ain't right, I would've thought it belonged on the secondary side of the transformer

 

[GoldDigger]

its a 200amp contactor, so it is large enough, I could not find a code reference one way or the other on the installation just thought it might be tucked away in a less than obvious location, the general consensus here is that it just ain't right, I would've thought it belonged on the secondary side of the transformer

Either side will effectively control the lights. But on the secondary you do not have to deal with the turn-on inrush, which can be 5-10 times the rated full load amps of the transformer.

You will almost certainly need OCPD and possibly a disconnect on the secondary side of the transformer, but that does not mean the contatcor has to be on that side too.

 

[rmitts]

Either side will effectively control the lights. But on the secondary you do not have to deal with the turn-on inrush, which can be 5-10 times the rated full load amps of the transformer.

You will almost certainly need OCPD and possibly a disconnect on the secondary side of the transformer, but that does not mean the contatcor has to be on that side too.

thanks for the response.

 

[iwire]

I am curious if there is a particular code reference that allows or disallows a contactor to control a transformer that feeds a lighting panel,
the 480v feed comes from the mcc to the lighting contactor( that is controlled by a photo eye) then to the 30kva transformer primary side, secondary to the lighting panel. contactor is in an unclassified area and the panel and transformer are located in a class1 division2 group D area

It is fine code wise and we see it done where there is a lot of 120 volt lighting in commercial buildings. No need waste electricity to run the transformer for the 12 hours a day when there is no load on it.