I'm replacing my dead old thermostat with a digital one. Only thing is the old thermostat is so old the wires did't have labels. I tried to just follow them by color but it didn't work. The only thing that did was when I switched the fan to on the furnace turned on. This thermostat is for heating only.

Here are the specs:

Old thermostat: so old there is no model number, only states that it's an electric clock thermostat by honeywell. The only other number I could find was T852A1C1 and that was in the inside of the housing.

New thermostat: Honeywell RTH230B

Wiring: four wires out of the wall (no electrical box); white, red , green, blue

What I did was: red to rh, w to w, g to g, and blue to yellow (even though it really makes no sense, but I found somewhere that it said blue is yellow)

Any help would be greatly appreciated

Thanks

Did the fan selector turn on the heating, or just the furnace blower? Check the connections at the furnace for what colors are connected to which lettered terminals.

I see many times the red is 24 volts, white is heat, green is fan, and blue is cool(to compressor contactor. Since this had a clock and no cool, the blue/yellow may be the other side of 24 volts.
I would look inside unit where contro wires attach, may shed some light. A couple of good AC guys here may provide some more/better info.

Quote:

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Originally Posted by KC13

Did the fan selector turn on the heating, or just the furnace blower? Check the connections at the furnace for what colors are connected to which lettered terminals.

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I'm not sure I know the difference between heating and furnace blower, I can tell you that when it was switched on the temp just kept rising and the heat didn't stop at the temp set

I tried to see which wire is connected to what but honestly their not any better when showing what's connected to what

Connection between the red and green likely? Will run blower, connecting the white(which I see as mostly) for Heat should activate the Heat Contactor.
Be careful not to Have heat on without the blower.
At this point, I would open the unit to see where the other end of the control wires connect to, or determine at thermostat wires.
You could use a meter or continuity tester to verify the thermostat is making and breaking the Heat(White(W)) terminal with the Rh.

Apparently the red and green wires activate heating when connected. Though miswired, it doesn't appear that you burned anything up, so you may be close. Ideally, the wire connections at the furnace should be identified to assure proper function. This scenario, unfortunately, leads to equipment component failure quite often, and greater expense to the homeowner. If you are having difficulty, you should probably bring in a pro.

Well I tried out red and green, are to rh and g to w, it works. But what do I do with the w and the blue wire?

And if I were to test for connectivity what am I looking for?

Thanks

OK, this is what I have working right now, are to rh, g to w, w to why and be to g. everything turns on and off when the temp is reached.

I tried switching w and be and nothing turns on when that is set-up.

Could someone just verify that how I have the wires currently set up should work?

Its still not too late to look inside unit to see if they are even hooked up.
Sounds like you have it. Not everyone uses the same color code.
I see Electricians use the blue/white and the orange/white for the red and green on phone jacks when using Cat 5 instead of the blue pair for line 1.

Yea, the wires are hooked up, but it's just hard to tell which wire is connected to what since, right off the bat I can see they used two different colored wires to connect to two other ones.

Well, as long as some one else can say that I probably have it, that's about what I'm looking for

Thanks again for your help

If it works with just the red and green connected, I would suggest leaving the others out of the equation since their function is unclear. Tape off the white and blue.