So I have older furnaces in my duplex (1247 series gas Hi-boy). Forced air and the heat worked fine until I had my HVAC guy install a/c this summer. He hooked the a/c up fine, even the FAN ON without COOL on works. But when I switch to heat the outside A/C compressors turn on. The pilot light is lit. Then I noticed the old two wires that are hooked up to the gas valve (Honeywell)were dangling to nothing - yeah, NOT connected! At the Honeywell transformer (R8239 A 1052) (in the furnace) I have 5 wires connected to R, C, W, G, Y.

Coming from the thermostat upstairs are the R,W,G, and the blue wire is connected to the Y screw.

Then there's two wires going/coming to the compressor - a white a red --the red is connected to the Y screw with the blue wire. ---the white is connected to the C screw.

It also appears there's a jumper wire between the C screw and the G screw which goes behind the transformer.

Now on the gas valve are three screws: TH, TR, and THTR. Previous wires were hooked up to TH and to TR :that I know of.

First of all, what was wired wrong so the compressors kick on with the HEAT setting? And more importantly, what connection can I make from the gas valve to the transformer so I don't freeze?

BTW, I can't get my HVAC guy on the phone.

Thanks in advance to all:confused:

Themostat wiring sounds correct. Put the gas valve wires on th and thtr. See what happens. If the furnace works, but the outside unit still comes on, I would disconnect all thermostat wires from the board(red green white blue. Then jump the are and w terminals on the furnace board, see if the heat works without the outside unit coming on. If it does, you most likely have a short in the wires from the thermostat to the furnace. Please let me know what you find and I will try to help.




I completely mis-read your question. Sorry about the confusing advice.

themostat wiring sounds correct. Put the gas valve wires on th and thtr. See what happens. If the furnace works, but the outside unit still comes on, i would disconnect all thermostat wires from the board(red green white blue. Then jump the r and w terminals on the furnace board, see if the heat works without the outside unit coming on. If it does, you most likely have a short in the wires from the thermostat to the furnace. Please let me know what you find and i will try to help.


Thanks for the quick reply. But hook them to which screws on the transformer? Also, the previous wires on the valve were hooked up to TH and TR

If you follow the 2 old wires that were connected to the gas valve where do they go

If you follow the 2 old wires that were connected to the gas valve where do they go

They are only connected to the gas valve at the TH screw and the TR screw. They're hanging lose on the other end (the transformer). I can shut off the circuit breakers for the A/C outdoor units when I call for heat, but I don't know where to hook each wire up at the TRANSFORMER.

Here is A gas valve data sheet:

http://www.white-rodgers.com/wrdhom/pdfs/instruction_sheets/0037-5870.pdf

Note that in the schematic the high limit control. This has to be connected. It's the over temperature protection for the furnace.

Things can get a bit complicated because the high limit control locks out the gas valve and it determines when the burner ignites.

Two systems are generally in use. One where the high limit control controls the fan and even fan speed based on heat and it determines when the gas ignites, and turns off.

Example:
Call for heat
gas ignites, fan stays off
High limit detects a high enough temp and turns on fan
Call for heat ceases
Limit control keeps fan running until below a certain temp.

It also prevents the gas valve from opening when the plenum temp is exceeded. In this case there may be a reset button.

heating requires the low speed so to get this to happen with a 2 speed motor can be tricky.

It appears that to avoid this trickyness the newer furnaces use time. Call for heat. Turn on gas, wait x then turn off fan. Call for heat ceases, turn off gas, wait Y and turn off fan.

It's not a simple process and could be a dangerous one if done incorrectly.

I really don't like the answers so far. There is a definite lack of understanding.

I have to agree KISS. I misunderstood the question, and also gave the wrong advice on gas valve connection. Had a brain fart, not the first, not the last I'm sure, but I will try harder to fully understand questions before I give absurd advice in the future. Take care.