Can I

[JohnTheHeaterGuy]

I have an application where I want to control a 3 element 480V screwplug heater with a line duty DPST thermostat. The thermostat is rated for 277V. If I wire the elements in WYE, this means that each connection of the thermostat will see 277V - even though there are 480V across the two poles - the latter point is what is giving me an allergic reaction (and my manager too). Being a mechanical engineer, I know enough to be dangerous, so that's why I've joined the forum, so I can ask the experts to point me in the right direction. Has anybody seen this application before and if so, where would I be able to get the confirmation that this is acceptable.
thanks if advance for your input.

 

[GoldDigger]

I am allowing this post to collect design information, on the assumption that the actual installation will be done by a licensed electrician, whose input will also be obtained.

 

[garbo]

I am allowing this post to collect design information, on the assumption that the actual installation will be done by a licensed electrician, whose input will also be obtained.

Thanks for your commitment. I'm a second generation electrician that would give advice to friends & coworkers up to a point. Had a few co-workers who flipped houses and started doing own electrical work including replacing services then got mad when inspector failed them. I laughed when they wanted me to sell my soul ( pull an electrical permit ) and do drawings on how to do electrical work. Nope.

 

[LarryFine]

Welcome to the forum.

Two 277v contact sets in series can handle the L-L voltage.

 

[don_resqcapt19]

In my opinion you need a 3 pole device that is rated for 480 volts.

 

[LarryFine]

In my opinion you need a 3 pole device that is rated for 480 volts.

I thought, while disconnecting requires opening all lines, controlling does not.

 

[don_resqcapt19]

I thought, while disconnecting requires opening all lines, controlling does not.

Good, point, but I still would require the controlling device to be rated at 480 volts.

 

[petersonra]

I say yes if the 480 is a solidly grounded wye source and the common point of the heaters goes back to that neutral.

There might be some issues with spacing of the thermostat contacts.

Otherwise no.