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How to replace a high voltage thermostat with a low voltage thermostat?

How to replace a high voltage thermostat with a low voltage thermostat?


  #1  
Old 10-20-13, 10:21 PM
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How to replace a high voltage thermostat with a low voltage thermostat?

I have a 240v 7.5 kw heater in my garage. It has an internal high voltage thermostat. I can't set a specific temperature though. It just has a dial with dots on it. I want to replace the internal thermostat with a relay controlled by a wall mounted low voltage thermostat.

I know that I need to bypass the internal thermostat and put in a 40 amp relay with a 24v coil as well as a 110v to 24v transformer to send power to the thermostat.

So my problem/question, there is no common wire coming into the heater. All I have is two 110v legs (black & red) and a ground (green). So how do I wire in a transformer without a common wire? I know that I could send it down the ground, but for obvious reasons I don't want to do that.

Also, will I need a common wire for the relay as well?

If somebody could point me in the right direction I would be very appreciative.

I've attached two pic's in case that might help....
 
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  #2  
Old 10-21-13, 05:51 AM
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Old 10-21-13, 06:13 AM
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and I just put a wire nut on the white (common wire) coming off that transformer?
 
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Old 10-21-13, 06:54 AM
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Is there any reason why you wouldn't just get a line voltage T-stat and use it to break one leg of the coil for your existing contactor?
 
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Old 10-21-13, 07:04 AM
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I already ran a low voltage thermostat wire from where I want the thermostat to be, to the heater. The whole garage is finished and I don't want to redo drywall or have conduit or wires on the outside of the wall.
 
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Old 10-21-13, 07:09 AM
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Get the 240-24 volt transformer then a single pole contactor or a relay, with a 24 volt coil, use the contactor to break one leg of your existing contactor coil or replace your existing contactor with a 24 volt one.
 
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Old 10-21-13, 09:20 AM
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With that transformer use white and orange to L1 and L2 as you have 240 volts. Cap the black and red wires on the primary side.
 
  #8  
Old 10-24-13, 07:32 PM
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got it installed and it works great. Thanks guys!
 
 

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