Mixing voltages on the same contactor

[Swamp_Sparky]

I recently interviewed for a position with a local control panel builder, and during the interview process, the manager presented me with a set of drawings for a project currently under construction, with the intent of testing my knowledge of the components, etc.

One thing that jumped out at me while I was reviewing the drawing was a consistent use of contactors in the panel with a mix of voltages on them, i.e., the main contactor used both a 208v input on 2 connectors and the pos side of a 24vdc power supply through the other. Other contactors used 110v along with 24vdc in them. The 24v was also being used throughout the system as control power. Wiring was clearly identified, however I felt that this could be a serious personnel/equipment safety issue once the product is in the field. I can't find any specific prohibition against this practice, and was hoping someone could point me to a specific instruction either allowing or prohibiting this.

 

[Dennis Alwon]

There is nothing prohibiting it if it is identified properly and the wire is appropriate for the mix.

 

[raider1]

If the 24 volt system is a Class 2 system then 725.136 would prohibit installing Class 2 circuit conductors in the same enclosure as power or lighting conductors.

Chris

 

[Swamp_Sparky]

Thank you, gentlemen. If it's not directly prohibited, then I have no problem with it, other than concern for the end-user tech who may have to work on it. I still feel it would be safer if they isolated out all the 24vdc and provided it a separate contactor.

 

[kwired]

Would you have questioned this if the lower voltages were running through an aux contact instead of one of the power contacts?

I use 3 pole contactors in places where a 2 pole with an aux contact would work all the time. Cost is about same either way - less parts to keep in stock.

 

[Swamp_Sparky]

Would you have questioned this if the lower voltages were running through an aux contact instead of one of the power contacts?

You're correct, I would not have looked twice at it in that configuration. But, because it was specifically not setup that way, is what tweaked my concern.

Thanks again!