[tracey_reardon]

I am trying to wire a Honeywell RTH230B thermostat.

The existing wires are Yellow, Green, Red and Black

The ports available in the new system are W, Y, G and the Rc and Rh terminals are jumpered.

Which wire do I put in the W port? (Red or Black), then what do I do with the one that is not used?

Help!!

[labman]

If the furnace has the same R, W, G, and Y terminal markings, just match the wires to the same terminals at both ends. Usually the red wire comes from the 24 volt transformer and would be jumpered to RC and RH. Usually it is yellow to Y, green to G, and white to W. Likely it will be black to W.

If the furnace isn't marked that way, you are going to have to identify the transformer, heat, cool, and fan using any directions for the furnace you can find.

[theophile]

I have a similar question.

I also am trying to install the Honeywell RTH230B to replace an older "analog" Honeywell thermostat. I have 4 wires from the heating/AC unit and they are white, blue, red, and green. On the existing thermostat which works correctly, these are attached thusly:
Green -> G
White -> W
Blue -> Y
Red -> R
And there is a jumper between the Y terminal and a terminal labelled 1.

When I connected these wires to the RTH230B, I connected white to W, green to G, blue to Y, and red to RC which is jumpered to RH.

Wired like this, the only thing I can do is switch the fan on. When set in automatic mode and either heat or cooling, there is no way to get the system on. Even with the fan switched on, it only circulates the air, it doesn't turn on either the A/C or the furnace.

What am I missing? Thanks!

[labman]

I don't understand it. It mostly follows the standard convention except for the jumper on Y to 1, and a blue wire to Y instead of yellow. No problem if the blue wire connects to Y at the furnace too. Maybe better check that. Did the heat not come on at all, or did the blower delay confuse you into thinking it didn't come on? With things connected as you did, and the thermostat set for heat, there should be 24 volts AC between the white wire at the furnace and a B or C terminal at the furnace. If so, the thermostat is working.

[theophile]

Figured it out. I had it wired just fine. Turns out the batteries were low and the thermostat wasn't sending the "cool" and "heat" signals. Thanks!

[akcowgirl]

I am trying to install this thermostat to replace the old mercury ones. I have 3 wires coming from the old one; green, white and red. On the Honeywell thermostat they have the rh,rc,w,y,g, with a jumper in the rh,rc area. I hooked it up using the red in the in the Rh, white in the white and green in the green. I set the temp for 64 and in about 2 hrs it was climbing until it reached 83 degrees. Why is it still calling for heat? Did I wire it wrong? When I looked at the Furnace there are no markings for what wires are what, but only the green and white wires are connected the red one is coiled around and unused. PLEASE HELP.

[labman]

If you do a search here, you will find my answers really didn't solve similar problems for others. One reported a still not quite right solution by moving a jumper from HG to HE. Each situation is different. Let's start with the basics.

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.

Did you note what contacts the wires were connected to on the old thermostat? Were either connected to the R? It sounds like the green and white wires were connected one way or the other to the transformer and heat valve on the furnace, and to the R and W terminals at the furnace. If it is an older furnace, you can open it up and trace one wire to the transformer, and the other to a box between the gas line and burner. That is the gas valve. Connect the red wire to the transformer connection and the white one to the gas valve. Connect the red wire to the RC/RH terminal and the white to W at the thermostat. It should now work. If it doesn't, post back, and we will work some more on it. Where did you buy it? If they can't explain how to make it work, maybe they should take it back.

[akcowgirl]

Hey,
Thanks for the reply. The house was built in 2005, I looked at the furnace and the green and what wires are hooked up to an area that says "thermostat" the red wire is coiled around and not used. On the old thermostat the green wire was on the top, the white on the left and the red on the right. I spoke to the person that I thought hooked it up, he said that the old thermostat is numbered 4 on the rt, 5 on the lt and 6 on the top. Now I don't know what that means exactly. I also noticed that if you hook the old thermostat up and you cross the red and white wires that it keeps calling for heat. I can't understand why that would be unless that red wire is used somehow even though it's not hooked up on the furnace. I got the unit from Home Depot. I spoke to their "trained electrician" and he said that it shouldn't matter what order I put the wires in. I hooked it up and it seemed that it didn't work. So I took all of thermostats off and touched the wires together and I came up with 2 sets of wires that worked that turned on the heat. I hooked up those two wires and thought I had it solved, but I am thinking now that I didn't. I am at a loss. I live in Alaska and I am not fond of the heat so when the furnace doesn't kick off it's an ugly thing, but I guess equally as ugly when it doesn't kick on. I think it's time to call out the professionals. Thanks for your reply.

[dks37]

I just replaced an old coleman turndial thermostat with a new honeywell RTH230B. My old one was 2 wire.It says to hook the red to rh and white to w.I did this and set it to manual and it seems to want to keep running when I turn the thermostat down. Did I get my wires crossed or is there some program that I'm not doing right? :confused:

[labman]

You could go to the furnace and make sure the red wire comes off the transformer and the white goes to the gas valve. You can also try changing the batteries. However, several people have reported the same problem, and neither I, nor anyone else seems to have the answer. Honeywell has not seemed interested in helping others. I would go back where you bought it, and ask them to either help you make it work, or give you your money back. If they do help you make it work, you would be doing others here a big favor if you post back telling how.

[mikestorm]

I too am having a bit of a problem with a newly purchased Honeywell RTH230B thermostat. My house has a hot water (oil) heating system and no cooling system. I removed the existing manual honeywell dial-type and found three wires - red, white and black. Unfortunately, I cannot remember if they were all connected or if black was loose.

For my first pass at installation, I originally connected the wires like this:

Rh - red
Rc (jumpered to Rh)
W - white
Y
G - Black (I thought G meant "ground")

When I reassembled everything, the thermostat seemed to work in manual mode, but nothing seemed to work correctly in programmable mode (furnace wouldn't turn on when it was supposed to).

A quick search of the internet suggested I disconnect and tape off the black wire, leaving the two existing wire connections as-is. However, when I do that the furnace won't turn on at all, so I've reconnected black to G and left my thermosat in un-energy-star-compliant manual mode.

I'm convinced I'm doing something wrong. Any suggestions would be greatly appreciated.

EDIT: After reading this thread again, I'll check to see how the wiring is connected to the furnace. Hopefully that will shed some light on the situation.

[labman]

The red and white are correct. G is for fan only and Y for cooling. There are some other threads with that thermostat too. The only thing anybody has had much luck with is changing the battery.

[mikestorm]

I'm beginning to suspect it might be the thermostat. It works perfectly in manual mode. Programmable mode is just a glorified timer, with the functionality burden being completely that of the wall mount itself. That said, the only reason it wouldn't work are:

1) faulty thermostat
2) human error

I wouldn't rule either out, although I do have a masters in information systems, which, if I read the fine print of my degree, certifies me to be knowledgeable in setting programmable thermostats.

[mikestorm]

Okay, now I'm really confused. I checked the wiring at the furnace. There are two posts, both marked "T" (for Thermostat?). The black wire is connected to one post, the white wire is connected to the other post, and the red wire is hanging loose (picture below):

Knowing this, how should I connect the wiring to the thermostat itself. Again, my choices are:

Rh
Rc (jumped to Rh)
W
Y
G

As before, any help would be appreciated. Sorry for the blurry picture; I took it with my phone.

[labman]

OK the basics. Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.

For a thermostat to control the heat, you only need 2 wires, any old wires. Power from the transformer goes out one wire, and when the mercury ran to the proper end of the tube in the old ones, back the other wire to the gas valve, relay, etc. to produce heat.

A programmable thermostat that draws power from the transformer is more likely to work right if the wire from the transformer is connected to the RC and RH. With that model of thermostat, it is not a sure thing. You will have to poke around inside the boiler and see which wire goes where.

[mikestorm]

Well, I figured it out. Basically the problem was I had made things more complicated than they needed to be.

When I originally removed the existing manual thermostat, I had forgotton (until about an hour ago) that the red wire was still fully insulated and unconnected. Only the white and black were connected to the dial.

Since there were three distinct wires, and since the Honeywell instructions stated that the Rh post was instrumental in all thermostat installations, I assumed it was a three wire installation, so I stripped red and connected it to the Rh post. I then connected the White to W and the black to G.

When I pulled off the cover at the furnace and saw only white and black were connected there as well, at the time I had forgotten I had stripped red on the other end and so was dumbfounded.

Anyway, what jogged my memory was my reading another thermostat's installation manual (which was much better written than the honeywell). It said:

There is often no terminal marking on the existing thermostat of two wire, heat-only systems. Just connect either of the wires to the Rh terminal, then connect the other to the W terminal to complete the circuit.

So, I taped off red, removed the Rh, Rc jumper, connected black to Rh and white to W, and everything seems to be working.

[labman]

Glad somebody has one of those things working.

[Tyro]

I've got a boiler for heat as well (AC is a completely separate unit with it's own thermometer) and am trying to install the RTH230B. I've tried about every combination of connections with no luck. I can have the thermostat turn the heat on and never turn it off, turn it off and never turn it on, but can't get it to control both. It seems simple enough: there are three wires coming out of the wall for the thermostat: Red, White, and Blue (maybe green or black, but looks blue). If I short the Red and White, the heat switches on. If I disconnect them, the heat stays where it is (on). If I connect the Red and Blue, the heat turns off. If I disconnect them, the heat stays off. Red to White = ON, Red to Blue = OFF, Red to nothing = stay where it is, on or off. The old thermostat works accordingly: if I set it high, it connects R to W, if I set it low, it connects R to B. (It also has a 2200 ohm resistor between R and B, but I'm not sure if that's relevant.) I've taken a multimeter to the back of the new programmable thermostat and there are no connections that work accordingly. In other words, there is no pin (for the red wire) that gets shorted to one pin (for the White) when it's trying to heat, and another pin (for the Blue) when the heat should be off.

Am I missing something here? Is my boiler some kind of weird configuration? The new thermostat seems to want to make a connection for heat, and open that same connection to turn it off, not make another connection to turn it off. Anyone know what's going on?

[labman]

Snip....
Am I missing something here? Is my boiler some kind of weird configuration? The new thermostat seems to want to make a connection for heat, and open that same connection to turn it off, not make another connection to turn it off. Anyone know what's going on?

Fraid so. Most heating plants fire up when the thermostat switches the red to the white and shut off when it switches the power off. Sounds like yours requires the blue? Wire to be powered to shut off. In hot water systems, zone valves work that way. I see 2 options. Poke through the instructions and see if the thermostat give you the option of a double throw switch. Some of the old mercury tilt switches worked that way, one terminal or the other was always hot. The other option is to use the white wire to control the coil of a double throw relay. This is how zone valves work. You have common, NOC, and NCC. The red wire connects to the common, and the white wire and another wire from the other terminal of the transformer connect to the 2 coil terminals. Until the thermostat switches the red wire to the white, the red wire is connected to the NCC terminal. Power to the white wire switches the red wire to the NOC.

What you need to do is leave the blue wire disconnected at the thermostat. Install the relay at the furnace. Locate the red and maybe a different blue wire coming off the transformer. Connect them to the common and one coil terminal. Connect the white from the thermostat to the other coil terminal. Connect the blue wire that went to the thermostat to the NCC terminal.

If you scroll back, you can see a number of other people had similar problems and I wasn't much help. I wonder if more systems are wired like yours? Nobody said anything about the system shutting off when they connected the red wire to a blue? One. Usually the blue is the other side of the transformer and connecting them causes a short. Please post back and let me know what you find.

[klmgb]

Speaking of the RTH230B, I installed it no problem, but have lost the paperwork to tell me how to program it. Googled it but no help. Anyone know where I can get a copy?
Thanks