We recently had an electrostatic air filter installed on our natural gas forced air furnace (no air conditioning). The filter cleans the air so well, we'd like to run in "Fan Only" mode to clean the air on a regular basis, but not all the time. The original thermostat was a 2-wire type; the one I bought is a 4-wire type and has a "Fan Only" option. It looks like I either need to run a wire or two from the fan to the new thermostat (Honeywell CT51A) or maybe attach a jumper or two.

Any suggestions?
LD
LDavieau@yahoo.com

 

Need more info on your furnace what kind and what set up do you have there for the blower. Yes you need another wire to the tstat for the fan or you could wire it 110 at the furnace for the blower tobe turned on there. ED

 

The furnace is a 15-year old York Diamond 80 (80% efficient). The air filter is wired to receive power when the furnace is on, so maybe I'm over my head on this.
LD

 

LD:

If your furnace has amongst the low voltage connections a "G"
terminal it may be simple.
If you have this terminal and are comfortable working with low voltage wiring we may be able to help.

Let us know.

 

Greg,

There is a green terminal on the furnace, but that seems to be the last place the wires go. Working backwards from the furnace, they go to a humidifier and electrostatic air filter, then the thermostat.

Pulling a 4-conductor wire shouldn't be too hard, I can shut off the circuit breaker, connect the new wire to the existing wire where the thermostat is and pull it through to the basement then connect it through to the other devices. Would the white and black wire connections remain the same, with the green wire connecting only to the "G" terminals on the thermostat and furnace?

Thanks,
Lyle

 

On tstat and furnace 24 volts wire is

R Power
RH Heating transformer Power
RC Cooling transformer Power
W Heating load
Y Compressor
G Fan
W2 2nd stage of heating
Y2 2nd stage of cooling
C common

Id pull new 4 wire to the tstat. Fan on at the tstat should turn fan on for you. Dont foget in summer to turn the humidifier off when you have the fan running.Dont know just how the unit is wired but the filter and humidifier should turn on only when the fan turns on. Not when just the burner turns on. There should be a wire layout there on the blower door for this furnace. Sometimes the filter and humidifier are turned on by a sail switch or another relay in the furnace ED

 

Thank you to all who contributed!

With your help I was able to run the wire and make the connections needed to make the new thermostat work as I wanted. This is a real breakthrough for me, as I have mostly worked on automotive projects in the past and have not gotten into furnaces. This made your support all the more needed and welcome.

Once again, thanks!

Lyle