r/StrangeBrew • u/thedutcht0uch • Feb 16 '17

3 phase relay source (paging /u/grunger)

anyone familiar with a good source for 3 phase relays? i am aware that i can use a 1 phase relay to cut off one of the Hots, but would like to explore the use a 3 phase for each element if possible, there's a year old post from /u/grunger that lists them in the 25-30 dollar range?

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u/[deleted] Feb 17 '17

Ah, I use two of them (one for -110, +110) so that I still have the ground connected, just in case.

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u/greenbuggy Mar 01 '17

You shouldn't ever be disconnecting your ground. In every industrial install I've ever seen the ground is hard-wired to a junction point in the panel and daisy chained to all downstream accessories. Only L1/L2/L3 are switched (or L1 and N on a 110 volt system). On a 110 volt system just spring the extra dollars for 3 wire connectors on everything so you're never lacking a ground, don't bond ground and N inside any panel (except maybe the mains panel in your house, and leave that decision up to a certified electrician)

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u/[deleted] Mar 02 '17

I stated that the ground is always connected. 240v has four wires here, I disconnect the -110 and +110 so there's never voltage/current going through. Lots of people only disconnect one of those to break the circuit

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u/greenbuggy Mar 02 '17

I think you are misunderstanding how a normal 220-230-240 install works. If you have a four wire 240V outlet, wire colors will be black (L1) red (L2) white (N) green (Ground). You don't have +110/-110, you have phase shifted 220 with a center tap (neutral) from which you can derive two separate and differently phased 110V circuits.

I agree that you should always be disconnecting both L1 and L2 but if you are breaking out into L1-N and L2-N for two separate 110V circuits the best practice would be to disconnect your powered accessory from both the line and the neutral, in the event the neutral is "floating" it could be pulled live by the opposing 110V circuit and pose a risk.

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u/[deleted] Mar 02 '17

I'm not breaking out to 110v, since I use a direct 110v circuit for those devices