Two Sources on a Snap switch

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wireguy8169

Senior Member
Location
Southern Maine
First let me say that I am not in favor of doing the installation the way I am going to explain it and may not have to but here is what my boss wants to do:

We have a clairifier in one of our waste water treatment facilities, we have rebuilt it and its ready to be installed. An underlying issue is we have to be concerned with is that it will not ever be turned on so my boss had the idea of putting the overhead light and exhaust on the same switch. For some reason he is not infavor of a timer but hey whatever.
The lighting is 277V and the Exhaust is 120V.

I am not a big fan of mixing systems in raceway's or enclosures but realize it is permitted, what I am really not liking is putting two systems on the snap switch regardless of all the labeling in the world. Art. 404.9 Does allow you to put two or three circuits on a mulitpole snap switch as long as it is listed and marked. Any input is appreciated but I think I am mainly just venting :D and sharing.

Thanks
 
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RUWired

Senior Member
Location
Pa.
(2008) article 404.8(C) prohibits two sources feeding a multipole switch unless the switch is rated for a multi circuit use or the rating of the switch is not less than the line to line voltage of the system suppling the circuits (480 volts in this case)

Rick
 
kwired

kwired

Electron manager
Location
NE Nebraska
If you want both loads controlled by a single switch use the switch to control contactors to run the loads. Or have the 120 volt circuit supply the switch and the 120 volt load as well as a contactor for the 277 volt load.
 
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wireguy8169

Senior Member
Location
Southern Maine
kwired said:
If you want both loads controlled by a single switch use the switch to control contactors to run the loads. Or have the 120 volt circuit supply the switch and the 120 volt load as well as a contactor for the 277 volt load.
Click to expand...

Thanks

kwired, I had thought about controling the contactor for the fan (its in a different location about 500 feet away) but would have been too much with trying to get the wiring there, but I could put in a box and put a small contactor to control the light. This is why I really appreciate this site. Sometimes my own brain gets in the way I was so focused on the different supplys that I did not think the problem through all the way for different solutions.

Thanks again
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
If you look at most any standard two pole snap switch it will say 'single circuit use only' or some other such wording.
 
S

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
kwired said:
If you want both loads controlled by a single switch use the switch to control contactors to run the loads. Or have the 120 volt circuit supply the switch and the 120 volt load as well as a contactor for the 277 volt load.
Click to expand...
I just finished a similar job that I designed. Existing building, adding a whole room exhaust fan to be on any time the lights were on. Also required a break glass e-stop outside the building. So I just bought a Square D 8501K class relay with a 120 volt coil. Ran the existing light switch leg through the E-stop to the coil and the dedicated circuit for the fan through the contacts.

Reading the OP's second post newer than this one though, I wonder if he may need a different design. He mentioned that there is a contactor for the fan and it was far away. I would not design a relay remote from the fan, unless maybe it was mounted over the feeding panel. Not saying iit is illegal, but I would feel it was a poor design. The OP should connect to the fan contactors coil with the switch leg of the lights somehow, if I understand his situation.

What do you think?
 
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