220V relay question

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Old 08-06-09, 09:38 PM
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220V relay question

I'm trying to wire a thermostat relay (24V coil) to control a 220V A/C unit. The whole unit runs off of two 'hot' wires, one black, one white (supposed to be black). My question is: what kind of relay (SPDT, DPST, DPDT, etc) do I need? I think I will need a DPDT, dual pole dual throw relay. If so, which wires go where?
 
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Old 08-07-09, 04:33 AM
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You would just need to get something like this Dayton 2UTL4 Definite Purpose Contactor with a 24 volt coil. You can get one like this or a 2 pole.
Your line leads would just terminate on the top 2 poles and load out of the bottom. Of course your 24 volts would terminate on the coil.
It would also need to be in some sort of enclosure.
 
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Old 08-07-09, 11:18 AM
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Thanks a lot, I definitely need a definite purpose contactor like you said; smaller DPDT relays won't handle the amperage I'm needing. Another question, though: when I was trying to wire it to a smaller relay, sometimes the breaker would throw, sort of. It wouldn't go all the way to the "on" position. I would change up my wiring, re-throw it, and it would be fine. What does it mean when a breaker is doing this?
 
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Old 08-08-09, 03:43 AM
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Sounds like there was a dead short in your wiring.
 
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Old 08-08-09, 09:35 PM
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Yep, that was it. I had it wired with a single-pole switch, and one way I had it, it must have been connecting black (120V positive) to white (120V negative), throwing the breaker. Thanks a lot. Let me just be sure, 2 pole contactor, 220V: black and white line in the top, black and white load out the bottom, 24V lines wired to the coil, no thrown breaker, correct?
 
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Old 08-09-09, 06:01 AM
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Sounds like you got it licked. Be sure to re-identify those white wires as ungrounded (tape with black/red tape or similar except green)Beer 4U2
 
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Old 08-09-09, 09:38 PM
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Thanks a lot. I'll definitely re-label the wires. It would have saved me a lot of guesswork if they were colored correctly in the first place.
 
 

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