McQuay


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Old 12-16-14, 09:44 AM
J
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McQuay

Hi Guys,

I have a 20 Ton Mcquay RTU heat and cool that uses the dual slider proportional thermostat as pictured. I am trying to replace it with a honeywell "Traditional" wifi thermostat but getting caugh up on the H/C Max, H/C Min wires in the slider tstat. Is their any way to use the traditional thermostat with this unit.

Current Tstat wires
1. Red H/C Max
2. Green H/C Min
3. Blue Cooling
4. White Heat
5. Brown Temp sensor wire1
6. Black Temp sensor wire2

Thanks!!

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  #2  
Old 12-16-14, 10:09 AM
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Welcome to the forums.

You can't just put that thermostat on the existing wiring. I'm not a pro on McQuay systems but there may be a way of using that thermostat if there is some type of communications board that can be removed. A full model number of the unit would be helpful.
 
  #3  
Old 12-16-14, 10:12 AM
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665404B-09 is the model number of the proportionate tstat, the new honeywell is RET97E5D.

thx.
 
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Old 12-16-14, 10:15 AM
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With proportionate, the higher the voltage the more heat it would send which makes me think if I send the full 5v back up the line, why don’t it assume I want full heat…. Lol

I don’t need a sliding scale for heat. I can give it the full 5volts on the line and it sends me all the heat. Well it should in theory anyway. Unless it also needs to see a balanced voltage on the cooling side at the same time as well…
 
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Old 12-16-14, 10:19 AM
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Theoretically I should be able to tie H/C Max to heat for full heat or to cooling for full cooling and not use H/C Min. but idk… I think more is happening under the hood lol
 
  #6  
Old 12-16-14, 08:59 PM
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You would probably need to use relays to install a conventional stat.
What is the model number of the air handler or package unit?
 
  #7  
Old 12-17-14, 05:14 AM
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Hi, I don't believe that stat is even compatible with the McQuay system the honeywell requires different a different voltage, doesn't vary voltages as required by MqQuay.McQuay has there own little nitch.
Geo
 
 

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