a/c thermostat wiring

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  #1  
Old 01-01-03, 07:44 PM
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Rob85
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a/c thermostat wiring

I have just finished wiring up a central a/c unit. I ran #6 wires from a 50 amp breaker to a 60 amp disconnect(non fusable) for the condensor. I ran #12 wires from a 20 amp breaker to the air handler.
Now I have to run the thermostat wires but I am not really sure about how many wires have to go were. The same thermostat will be controlling the baseboard heat and I have already run the wires to the furnace. But as I have said, not so sure about the wires that have to run between the a/c equipment and the thermostat.
Any help would be great.
 
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  #2  
Old 01-01-03, 09:53 PM
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hatchet
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I have used a 6strand phone wire for thermostats..either that or any type of 24 volt wire (twisted is ok). Your furnace will have letters on the terminal block as well as your thermostat. Essentially all you should have to do is match the letters to the color of wire. I can't remember but I think H was for heating C for cooling G for the Fan...etc. The wiring for your a/c unit should go to the furnace which in turn will use the same fan as the heating (thermostat to furnace - furnace to a/c). At least that is the way mine is setup.
 
  #3  
Old 01-02-03, 05:45 AM
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Rob85
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There is no fan for the heat, it is all hot water heat. So the fan for the a/c and the furnace arre two completely separate units. I am still not sure what to do. Can someone please help.
 
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Old 01-02-03, 05:50 AM
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I believe you'll have to have 2 separate thermostats with 2 sets of wires.
 
  #5  
Old 01-02-03, 09:11 AM
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Rob85
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No, one heat/ a/c thermostat will do it, I just don't know how to wire up the a/c part of the thermostat.
Can anyone else help
Thanks
 
  #6  
Old 01-02-03, 09:15 AM
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A thermostat will use the common wire for both head and AC. If you have 2 separate heating systems then you'll have 2 common wires. Unless there are special thermostats out there I'm not sure how you'll manage that.
 
  #7  
Old 01-02-03, 10:52 AM
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Use a M-H Heating/Cooling Thermosatat with seperate RC and RH terminals and 2 M-H fan relays each equipped with a 24 volt transformer and double-pole double-throw contacts for maximum circuit "flexibility".For "Cooling", the Thermostat makes RC-to-Y which operates the "Cooling" fan relay and the 24 volt compressor contactor which is powered from the "Cooling" relay transformer. For "Heating", the thermostat makes RH-to-W which operates the "Heating" relay.The double-pole double-throw relay contacts can control blowers and circuits associated with the Heating/Cooling operation. Run at least 4 wires to the thermostat with the colors Red-White-Yellow-Green.I suggest you visit a HVAC supply-house for product and other information and advise. You also can refer your question to the "Heating/Cooling" Section of the Forum------Good Luck!!!!
 
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