Replacing thermostat 4 wire to 5 wire. Help!!!


  #1  
Old 01-26-09, 06:54 PM
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Question Replacing thermostat 4 wire to 5 wire. Help!!!

Hello,

I am replacing an old White-Rodgers 1F56-310 thermostat with a new (somewhat unknown brand) TotalLine TotalTouch P286-1500. I have included the links to the manuals for these thermostats.

The problem is that the new one requires 5 wires, whereas the old one only used 4. Unfortunately I only have 4 wires going from my furnace to the thermostat. Any suggestions on how I can avoid pulling a new wire?

Here is how the old thermostat was wired:
Red went to RH and RC (which are also shorted by a jumper)
Green went to G
White went to W
Blue went to Y

According to the manual of the new thermostat I need to connect:
24V (Red) to RH
Fan (Green) to G
Heat (White) to W2
AC (Yellow) to Y1
and Common (Blue) to C.

It is that Common wire that I am missing... I tried attaching everything except for that missing wire but the heat/cool options in the thermostat did not activate. No surprise, because according to their help (link attached), if one has a gas furnace, the Common wire MUST BE CONNECTED.

I have a gas furnace and an AC - pretty simple setup. Can I do anything to get this thermostat to work? Pulling a new wire does not seem like an easy task...

Thank you!
 
  #2  
Old 01-26-09, 09:11 PM
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You should asking this in the heating forum. But than likely the "C" terminal is like the jumper wire on your old thermostat. In the new themostat a wire is connected from the RH terminal to the C terminal.
 
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Old 02-04-09, 08:05 PM
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I see that Bbyaka did go to the heating forum and get his thermostat wired but I wanted to address this for anyone that may stumble on this posting.

But than likely the "C" terminal is like the jumper wire on your old thermostat. In the new themostat a wire is connected from the RH terminal to the C terminal.
That is absolutely WRONG and will either blow the control fuse in the furnace (if a fuse is present) or burn out the control transformer.
 
 

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