I have been trying for days to get my Honeywell RTH-221b Thermostat to work with my AC. It's been working all winter for Heat, but now when I need it for cooling it does not work. I was able to take some pics of the old and new wiring.

This is the old wiring:

http://farm4.static.flickr.com/3652/3530086922_4885b03e76.jpg?v=0

This is the new wiring that works with Heat only.

http://farm3.static.flickr.com/2219/3529273627_d719acb174.jpg?v=0

So, the strange thing is that if I remove the jumper between Rc and Rh, then create my own jumper between Y and W on the Honeywell, I get AC. Although, now the Heat does not work.

Does anyone have ideas? I am not sure what to do, especially since I am unsure about the O wire connection from the previous stat.

Thanks,
Chris

Is this unit a heatpump?

Here is the normal wiring for a four wire thermostat. But the wires on the other end have to be places on the terminals that they are suppose to bo on.

At the thermostat; The red wire Goes on the Rh terminal.

The white wire goes on the W terminal.

The green wire goes on the G terminal.

The yellow wire goes to the Y terminal.

It is hard to tell by the pictures what color the wires are and just where they are going. But you have a terminal board at your furnace and what ever the color of wires are on those terminals you need to match them with the terminals on the thermostat.

Now there are two wires that go to the condensing unit out side. One of these wires connect on the board in the furnace to the Com terminal the other wire goes to the same terminal that the yellow wire from the thermostat is on. Remember that your colors may not be in the right place because if you jumper the W and Y wires you should not get anything.

Sorry about that.

OLD Stat:

* Orange to W
* Black to 0
* Black to G
* Yellow to Rc

NEW Stat:

* Orange to W
* Black to Y
* Black to G
* Yellow to Rh (jumper to Rc)

Let me know if that helps.

Is this a ac or a heatpump? Do you have gas heat? Not sure why you have a O termanal

From you top pic it also looks like w is jumped to y is that correct?

Yes, W is jumped to Y, which looks like is jumped to something else. This is electric heat on a Train Heat/AC unit. I am not sure if it has a heat pump.

The good thing is that the old wiring (top pic) works perfect. I just don't know how to wire the new honeywell.

Chris

Does your new stat have a O?? When you turn the heat on with your old stat does the outdoor unit come on? If you have no O Tremanal then odds are that stat will not work for you if in fact you have a heatpump.

I am in a large apartment building. I can hear the compressor come on when the Cooling works, same with the Heat. It makes a click and starts the whirring.

The building does have large units on top of the building. I have no idea how that works though.

OK, sounds like you may have a heatpump then. That is why the w and y are jumpered

Sorry about that.

OLD Stat:

* Orange to W
* Black to 0
* Black to G
* Yellow to Rc

NEW Stat:

* Orange to W
* Black to Y
* Black to G
* Yellow to Rh (jumper to Rc)

Let me know if that helps.

I think on the old thermostat that you have a black wire and a green wire, so check it out and see if maybe the green wire is connected to the O terminal. If it is switch the wires on the Y and G terminals.

R-RH^RC
W-W
Y-Y
G-G

RH is the power for heating
RC is the power for cooling

if you have both an R and RH wire (meaning one wire coming out of your wall going to R (RH) and a separate wire coming out of your wall going to RC) then u MUST remove the jumper from RH^RC

most Honeywell thermostats come with the jumper already installed between the RH&RC terminal.


-Eboni B.