Hi All,

This seems like the hottest place for Honeywell RTH230B questions, so I thought I would post what worked for me after much reading on this forum and troubleshooting.

My old thermostat had five wires: read, white, yellow, green, blue

The Honeywell connections for: Rh, Rc, W, Y, G

My system: central AC (not heat pump), forced hot water heat from a boiler

My problem: after leaving the jumper installed and the blue unconnected: setting the thermostat to activate heat turned on the fan but no heat

For this particular system leaving the blue wire unconnected didn't work. Put the blue wire on the W connection (which didn't work with a white wire connected) and things started working.

Troubleshooting tip: to see which wires control what I used needle nose plyers in the terminal block to verify that connecting red-to-green makes the fan come on and that connecting red-to-yellow activates the AC compressor. I couldn't tell if the solenoid to let the hot water enter the coils was coming on, and just assumed it worked until it got cold and I needed it. The right way to do this would be to trace the wires out and see what they are connected to, but laziness prevailed.

I would not recommend this therostat for a 5-wire system.

- James B

Shorting out control wires while still connected to a thermostat, especially a digital, is not recommended. This can cause transient voltages, thou very small, to damage internal components.

To test operation of control wires, leave the wires off any thermostat, and just put the wires together. This will simulate a switch closure, which is all a thermostat is, several switches.

Note this is
ONLY FOR LOW VOLTAGE SYSTEMS.
DO NOT DO THIS WITH 120 VOLTS OR HIGHER.

The combination of wires you had are your alone, and will be different for many people, and are not standard color code. The color code on the thermostat is the "standard", but with low voltage wiring, is not necessarily followed, and certainly not enforced.

Hi All,

This seems like the hottest place for Honeywell RTH230B questions, so I thought I would post what worked for me after much reading on this forum and troubleshooting.

My old thermostat had five wires: read, white, yellow, green, blue

The Honeywell connections for: Rh, Rc, W, Y, G

My system: central AC (not heat pump), forced hot water heat from a boiler

My problem: after leaving the jumper installed and the blue unconnected: setting the thermostat to activate heat turned on the fan but no heat

For this particular system leaving the blue wire unconnected didn't work. Put the blue wire on the W connection (which didn't work with a white wire connected) and things started working.

Troubleshooting tip: to see which wires control what I used needle nose plyers in the terminal block to verify that connecting red-to-green makes the fan come on and that connecting red-to-yellow activates the AC compressor. I couldn't tell if the solenoid to let the hot water enter the coils was coming on, and just assumed it worked until it got cold and I needed it. The right way to do this would be to trace the wires out and see what they are connected to, but laziness prevailed.

I would not recommend this therostat for a 5-wire system.

- James B
Thank you for the tip.figured I could wire,bypassing stat.I app. The help,I guess I should get another stat?

Hi All,

This seems like the hottest place for Honeywell RTH230B questions, so I thought I would post what worked for me after much reading on this forum and troubleshooting.

My old thermostat had five wires: read, white, yellow, green, blue

The Honeywell connections for: Rh, Rc, W, Y, G

My system: central AC (not heat pump), forced hot water heat from a boiler

My problem: after leaving the jumper installed and the blue unconnected: setting the thermostat to activate heat turned on the fan but no heat

For this particular system leaving the blue wire unconnected didn't work. Put the blue wire on the W connection (which didn't work with a white wire connected) and things started working.

Troubleshooting tip: to see which wires control what I used needle nose plyers in the terminal block to verify that connecting red-to-green makes the fan come on and that connecting red-to-yellow activates the AC compressor. I couldn't tell if the solenoid to let the hot water enter the coils was coming on, and just assumed it worked until it got cold and I needed it. The right way to do this would be to trace the wires out and see what they are connected to, but laziness prevailed.

I would not recommend this therostat for a 5-wire system.

- James B
Thanks for the help,I tried the red to y and outside unit runs then stops as the breaker trips,so I guess is safe to assume there is another problem,thank you

thanks for the help,I tried the red to y and outside unit runs then stops as the breaker trips,so I guess is safe to asume there is another problem,thank you


Speaking of problems with this model of thermostat- mine has a mind of its own! When the heat is supposed to come on, the heat icon comes on, but that's it. I have to turn the unit off and flip the breakers on the heating/colling unit 2-6 times and keep trying it. Then it will come on. This morning the temp was 58 degrees in my house and it is supposed to keep the house at 70. This problem became worse over the past 2 weeks. I have changed the batteries, even though the change battery icon was not showing and this appears to help (knock on wood). Any suggestions? I have a Frigidiare heating/cooling unit, model number B2Bm042K-B, installed when the house was built in 1999. Thanks!

polady, my system is very similar. It usually happens the first part of the cool season. The heat was working fine while it was moderately cool, but when it drops into the 30s the heat will just not come on. But if I wait until later in the day when it warms up a little it will start working. So I wonder if all the stuff you are doing by flipping breakers, changing batteries, etc is just taking the time needed for it to warm up a little and then start working. I just put in this thermostat a couple of months ago because my old one was getting corroded too much around the battery area.

This actually happened with our old thermostat too and our entire unit was replaced just a few years ago. So I wonder if it is something with the unit and not the thermostat. The cooling works fine, and the fan works on auto if the heat is in the off position.

Still searching.