I recently installed two new programmable thermostats in my house, one for the upstairs unit, one for the downstairs unit. The upstairs functions great. It's a bit different on the first floor...

I programmed the unit to keep the heat at 62 during the night and bring it up to 68 at 6am. The unit kicks on at 6am (as it should) and runs for about 30 minutes and then shuts off.

I thought it wasn't getting enough air and changed the filter - same issue occurs. There is also no water in the condensate pump. If I turn the unit off and turn it back on from the breaker it fires up. I've checked the wiring on the thermostat and it sure looks correct.

In the unit I can see the second LED light flashing. (Pressure valve?? )

I can't imagine the unit is overheating and is shutting itself off for safety. I'm in Atlanta and it doesn't get all that cold here. Any advice would be greatly appreciated.

It would be nice to know the make and model number of the unit you are talking about.

How many blinks/flashes are you getting?

My bad, sorry.

It's a Rheem Classic 90 Plus only about four/five years old.

The middle of three LED light blinks on and off for one second intervals. The unit will reset itself and kick back on after about 30-40 minutes.

Rheem has had problems with there pressure switch. I believe they are covered by a 5 year warranty but not sure.

You did not state what brand and model thermostat you have. Some have adjustable heat anticipator settings or heat type selections if it is a new programmable type. This could be some of the problem.


Error Codes
A green LED indicates system faults
Steady On: System OK
Steady OFF: Board control fault or no power applied
1 Flash: Ignition failure (control in one-hour lockout)
2 Flashes: Pressure switch fault, fails open (switch is
Stuck open)
3 Flashes: Limit switch open (main or auxiliary)
4 Flashes: Pressure switch fault, fails closed (switch is
Stuck closed)
A yellow LED indicates flame status
Steady on: Normal flame is sensed
Flashes: As flame weakens, frequency of LED flashes increases.

The blink codes are on the wiring diagram usually on the inside of the blower door.

The unit is a model 1x2000 and the thermostat is a Hunter 44860. I opened the access panel and noticed that there are 3 lights: from left to right, 1) flame 2) OK 3) PWR. It is the "OK" light that blinks. So reading the flow chart it would appear something is up with either the pressure switch or limit switch. Or could there be something with the wiring at the thermostat? I feel like I have checked that thoroughly.

One way to test the thermostat is to disconnect the heat wires and jump the two together. That will temporary take the thermostat out of the mix. If the furnace runs correctly with the heat only wires jumped or connected together then it will be a thermostat problem.

If it still acts the same then it is probably the pressure switch.

QUESTION? Did the furnace work OK before you changed the thermostat?

Yes, the furnace worked fine before changing to the new thermostat. However, I have the same unit upstairs and it runs like a champ with the new thermostat.

The thermostat must be wired wrong OR the thermostat is bad. One thing that can also cause this problem is if the witing to the thermostat is shorted or the bare wires are touching. You might check your work in the thermostat area of the wiring since it is easy to short there and it was the last place you changed the wiring at for the new thermostat.

Try switching the thermostats from downstairs to upstairs and see if the problem moves with it.

Sorry I haven't replied, it hasn't been cold enough to kick on the furnace lately. The last time the unit tripped, the LED flashed 1 time and then a 2 sec pause which indicates a 1 hour lockdown.

I've checked the wiring and everything is connect and no bare wires.

The time it takes the unit to shutdown varies, anywhere from running for 30 min or over 1 hour.

Thanks,
Craig