thermostat wiring

[ChrisNiemann]

well ya'll vintage posters have been a bunch of help with my 93 so i guess i post here more often now...

i have my furnace thermostat in the back bedroom, i was thinking of replacing it with a programmable one instead of the old 1890 style one that has the metal coil that heats up (thats efficient lol)

anyway, when i took it off the wall, i had only 2 wires on the back of it...

how do i replace this with a thermostat that usually requires like 5 wires...

Thanks Again for the help!

[Gary - K7GLD]

The few replacement thermostats I have dealt with usually have various alternate wiring schematics included in their installation directions - probably no "one-size-fits-all" recommendations for the many replacement brands/types of thermostats anyway...

[Steve & Bunny]

Originally Posted by ChrisNiemann

well ya'll vintage posters have been a bunch of help with my 93 so i guess i post here more often now...

i have my furnace thermostat in the back bedroom, i was thinking of replacing it with a programmable one instead of the old 1890 style one that has the metal coil that heats up (thats efficient lol)

anyway, when i took it off the wall, i had only 2 wires on the back of it...

how do i replace this with a thermostat that usually requires like 5 wires...

Thanks Again for the help!

The old 1890 style? That would be the one shaped like a coal shovel? Anyhow, if you find a thermostat you like at Lowe's or anyplace like that, all you need to do is hook one of those wires to the W(hite) terminal and one to the RH (red heat) terminal. You just ignore the rest of the terminals. When I replace thermostats in RVs, I usually get the non-programmable digital ones, because they're easier to set. The wiring is the same, though.
Have Fun!
Steve

[a k]

You also need to run a common off the transformer to the C terminal for the program to work.

[ChrisNiemann]

Originally Posted by a k

You also need to run a common off the transformer to the C terminal for the program to work.

why would i need that? i mean what does that do? i thought the program part was all kept by the batteries and the thermostat, when the program was "on" it would allow the furnace to kick on and run until desired temp.... what does the common do for it?

not arguing, just learning!

["007"]

A five wire therm maybe for a AC system control and other fan controls for AC & HEAT you only need 2 wires to put your furnace on they have digital two wires, you need not pay for the more costly version.
If that is what you have just look at instructions for therm should tell you what two wire connections needed.

[Steve & Bunny]

In an RV you typically don't have a transformer involved. That would be a 24v AC controlled furnace, usually found in a home and sometimes in a park model RV. 007 is right.

Steve

[ChrisNiemann]

thank you 007

now, where would i find these 2 wire programmable therms? MY wal-mart sure as crap ain't got them! lol and yes, i only need heat, the a/c i would like to upgrade as well to a program but it seems a bit more complicated with a multi fan setting... especially since the wiring harness for it is a plastic clip, which means i would have to cut that off (no scared there, i have about 200' of extra wire) but just nervous that it wouldn't work....

[Steve & Bunny]

Chris,
In my first email, what I was saying is it doesn't matter how many wires the thermostat can use. The only thing you care about on the thermostat is the "RH" (red heat) wire, and the "w" (white) wire. You probably won't be able to find one for just heat, so you ignore the "Cool" connections, which, depending on the thermostat, may or may not include multiple fan speeds.
The furnace controls its own fan, the thermostat is just a switch that either connects or disconnects the two wires you have at your old thermostat. If you connect those two wires together and leave them connected for about 30 seconds, the furnace will start by blowing cold air. About 30 seconds after that it will start its burner and begin heating. When you disconnect those two wires the furnace will continue to blow for another minute or two without fire, to cool things down. Of course the cycle I just described assumes the furnace is working correctly to begin with.
The air conditioner has at least three wires, and sometimes lots more. I think the most I've seen is nine. In some installations the furnace is controlled through the same control unit as the AC. These can be a real challenge to modify - you don't want to go there.

Good luck,
Steve

[ChrisNiemann]

yeah, i ain't goin there. my a/c unit is up front, heat is in the rear so i'll just get a program for the rear to do the heat, ignore the cool and be done.

then later i might dig into getting another one for the a/c up front and splice into those lines and see what i can do.

thanks again for the help everyone!! I LOVE THIS SITE!

p.s. and yes, the furnace is working wonderful, just the old thermostat was a bit (11 degrees) off....

[Gary - K7GLD]

Originally Posted by ChrisNiemann

thank you 007

now, where would i find these 2 wire programmable therms? MY wal-mart sure as crap ain't got them! lol and yes, i only need heat, the a/c i would like to upgrade as well to a program but it seems a bit more complicated with a multi fan setting... especially since the wiring harness for it is a plastic clip, which means i would have to cut that off (no scared there, i have about 200' of extra wire) but just nervous that it wouldn't work....

I got our NON programmable T-stat replacement - a Hunter brand, at Walmart not all that long ago - was set up to handle 5 wires as I recall, for both heating and cooling control, but of course, I only needed the 2 for heat control. It works FAR better than the failed OEM it replaced...

Then of course, there's always that good 'ol Internet search feature, on "programmable thermostats"...

[ChrisNiemann]

not going any other route other than program..... i'm not in it enough during the day but when i get back in the evening/nights i hate that it's so cold in there.... so i have to go program....

[justustwo]

Not to hijack this tread but how do you turn thease stats off when not in use?

[Steve & Bunny]

Just put the switch in the "OFF" position.