Question about Honeywell Programmable Thermostat Heater

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Honeywell RTH 230B Thermostat Wiring

Help!!!!!! I bought the above programmable thermostat to replace an old HW mercury thermostat. I thought it would be an easy switch..wrong!

I have an oil-fired furnace - heat only - no A/C units. On tactual furnace, there is a White wire and Blue wire connected to each of two "Thermostat" terminals (both unmarked)

The old mercury thermostat I removed was connected by two wires (blue to one unmarked terminal and white to the other unmarked terminal). There was a red wire loose and unconnected/unstripped.

I installed the HW prog. thermostat.

On the new one the connections are Rh Rc (jumpered) W Y G.

Following the instructions for 2 wire installation (I assumed since the old once was hooked with two wires, the new one was also a 2-wire installation), I removed the jumper from Rh/Rc. (correct??)

Since there were no wiring instructions with the Thermostat (duh??!) I guessed and connected them as follows:

Blue to RH
White to W

Left the red hanging as per the original.

The ambient room temp was 76 degrees. When I change the set point to 82 and switch to "heat" to test the furnace, nothing happens.

I've tried the wires in a few diferent spots but nothing!!

do I have to now use the red wire in the new thermostat??
should I have removed the jumper?? (I have a second unit with jumper intact if need to use it).

Can anyone tell me how to connect it using the colored wires I have before I jump off a cliff!!

Thank you so much in advance,


Posted by on

  • keywest508 Nov 14, 2008

    Somewhat the same. I hooked the red to the area for the red and white to the terminal for white and removed the jumper. Increased temp above room temp, boiler started for about 60 secs and turned off. Any thoughts ?



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Put the jumper back in RC and RH and that should do it.

Posted on Apr 15, 2009


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