Im running 2-240v 40 amp circuits to feed 3 receptacles. This is to run 2 UV lights and one small conveyor belt. The UV lights are each pulling 14 amps and the conveyor 10 amps. I plan on pig tailing one circuit to 2 receptacles for the lights and the other circuit for the conveyor. Im wondering if I can use 10/4 cable using black and white (white marked as hot of course) for one circuit and red and blue for the other circuit. Can I use the same ground wire for both circuits? Or do I have to run 2 separate cables, like 10/2 for each circuit?
Can I use one ground for 2-240 circuits
1 - 9 of 9 Posts
Your plan works fine with a shared grounding conductor. Only one grounding conductor is required in each cable or conduit, as long as it is sized to the largest circuit it's protecting.
However, #10 wire is not generally good for 40A. It's generally only suitable for a 30A circuit, with some limited exceptions - which are quite specific.
I am also questioning the 40A circuit for the 10A conveyor load. Does the conveyor require a smaller breaker? It may or may not be allowable on a 40A circuit.
However, #10 wire is not generally good for 40A. It's generally only suitable for a 30A circuit, with some limited exceptions - which are quite specific.
I am also questioning the 40A circuit for the 10A conveyor load. Does the conveyor require a smaller breaker? It may or may not be allowable on a 40A circuit.
I've never seen it in person, but it is a list product from Southwire: https://images.homedepot-static.com/catalog/pdfImages/1c/1ce8f017-ba7e-430f-9889-2f04964995b1.pdf
And Encore: https://encorewire-prod.imgix.net/m...eets/copper/residential/EncoreWire-CU-NMB.pdf
Joined
·
3,257 Posts
12/3 for the conveyor and 8/3 for the lights will do.
They have to be 50A receptacles. And there can only be one of them per circuit. I gather that's not going to work for your requirement. Then you need to do something else.
OK, you generally can't dogpile a bunch of <16A loads onto a single 40A circuit. In a commercial application you can sometimes do this with lighting using the Tap Rules, but the loads must be hardwired.
What you can do is install a subpanel out at the remote location, and then have 15/20A breakers in the sub feeding the various loads. Get a big sub; remember your 240V loads will gobble 2 spaces each. You do not need to run a neutral wire if all the subpanel loads are 240V, but you might be glad you did.
#10 wire is a no-go on a 40A circuit because of NEC 240.4(D). You must use #8 (Cu or Al).
Yes, if you solve the other problems.
Most commercial installations require conduit anyway. If you run EMT metal conduit, that is your ground, and you can run anything you please in the pipe, up to 4 single-phase circuits.
Joined
·
794 Posts
The International Electrical Code only allows circuits of 20A less to have multiple receptacles.
The National Electrical Code doesn't have that restriction.
It depends on which Code is recognized in your area.
NEC doesn't restrict 30A receps like that, which was a true surprise for those of us on diy.SE who researched it pretty exhaustively. However, for 50A receptacles, yes. I don't have the research at the tip of my fingers but I'm confident in it.
Regardless, you can't put a 50A plug on a 14A load. When UL approved it, they assumed a breaker behind it would have the trip curve of a 20A breaker. Say there's a 500% overcurrent, so 100A. A 50A breaker will trip in 8-33 seconds. A 20A breaker will take 1-3 seconds. Big difference!
A 300% overcurrent (60A) may never trip a 50A breaker.
1 - 9 of 9 Posts
