Upgrade thermostat/optional Mach III + heater repair

[MTHook]

I'm trying to replace the slide TS with a digital. However the wiring is a bit different. The new TS shows 4 wires and my old one has 6. The colors match up until you get to the gray wire which.
The TS bar shows Blue, "O", Green,Yellow, white, Not used, Red, RC.
Honeywell says they don't go by wire color but function. Their functions are Red 24 volt power, Yellow Compressor, G fan, o/b is for reversing valve, C is common 24 volts, W is heat for furnace

Anyone have an idea is I should hook up the Blue then hope the "O" is gray?
The unit is an Airxcel 48000, TS is Honeywell RTH2300/RTH221
I thought this would be easy.

[2010Thor21RB]

Originally Posted by MTHook

I'm trying to replace the slide TS with a digital. However the wiring is a bit different. The new TS shows 4 wires and my old one has 6. The colors match up until you get to the gray wire which.
The TS bar shows Blue, "O", Green,Yellow, white, Not used, Red, RC.
Honeywell says they don't go by wire color but function. Their functions are Red 24 volt power, Yellow Compressor, G fan, o/b is for reversing valve, C is common 24 volts, W is heat for furnace

Anyone have an idea is I should hook up the Blue then hope the "O" is gray?
The unit is an Airxcel 48000, TS is Honeywell RTH2300/RTH221
I thought this would be easy.

The blue should be capped off if the thermostat is powered by batteries. The gray is your low speed fan. See the attached pic. If you want both fan speeds you'll have to put in a Single pole Double throw switch(SPDT) you only use yellow(Y) for compressor, white(W) for heat, red(R/RC) for power and Green Gray(G) for the fan( you can either just hook up the high or low and cap whichever one you dont use or do the switch add mod)

[2010Thor21RB]

Originally Posted by MTHook

I'm trying to replace the slide TS with a digital. However the wiring is a bit different. The new TS shows 4 wires and my old one has 6. The colors match up until you get to the gray wire which.
The TS bar shows Blue, "O", Green,Yellow, white, Not used, Red, RC.
Honeywell says they don't go by wire color but function. Their functions are Red 24 volt power, Yellow Compressor, G fan, o/b is for reversing valve, C is common 24 volts, W is heat for furnace

Anyone have an idea is I should hook up the Blue then hope the "O" is gray?
The unit is an Airxcel 48000, TS is Honeywell RTH2300/RTH221
I thought this would be easy.

I just did mine about 2 weeks ago. I was in the same boat[emoji2] here is a pic of mine.

[Chuck and Mary Ann]

While our furnace works well, we went the small electric heater route (two actually) and can use them where and when needed. not interested in chasing wires through walls - did that enough on a home and condo remodel!

[MTHook]

Thanks for the pictures and descriptions, Off to the store to get a switch. I think having the 2 speed fan is worth the extra time.

[16ACE27]

Originally Posted by Kickstand

Add 10ish amps for the furnace blower at the same time, and you’ll max out fast with other appliances. Not as much of a concern with 50amp and their oodles of available watts.

That's 10 ish DC amps which equates to 1 ish AC amps. Not a concern.