My first post. Just finished trying to troubleshoot a problem that I have with the heat pump reversing valve going back to air condition mode when the auxilliary heater goes off. With my voltmeter I determined that the 24 volts being supplied to the reversing valve (in heat mode) goes to zero when the thermostat cuts the auxilliary heater off. Hence, the unit continues to run in AC mode, cooling the place down. Hard to heat the place when the air conditioner is running! When the auxilliary heat kicks back in, the reversing valve is energized and goes back to heat mode. Had to stay up all nite switching the unit off as soon as the auxilliary heater had satisfied the thermostat, and then back on when I needed heat again. It's a Rheem heat pump. Any ideas would be appreciated?

 

Sounds to me like the contactor is stuck or you have a stat problem. If the heatpump call has stopped for heat, the compressor and all should shut down not just the reversing valve.

If you turn it off at the stat, does the outside unit shut off??

 

Yes, everything shuts down when I turn off the unit at the thermostat. Everything appears normal except the top set of mercury contacts in the stat is controlling both the auxilliary heat and the reversing valve. The bottom set of contacts control the rest of the system. Think the reversing valve needs to be controlled by the bottom set. During heatup, the reversing valve goes to air cond. as soon as the top set drops out so that the bottom set can never drop out and shut the unit down. Or, if I try to let it heat up without the aux. heat, I only get air cond. Could it be wired wrong? It's in a condo I just bought that had been used by many renters, so I'm not sure it was ever right. I'm thinking it's either this or something wrong with the defrost board.

 

Id say first the wire in at the tstat dont sound right.
#1 At this time of year why is the AUX or EM comeing on
#2 With no power to the R/V valve it should be in heat mode

Dont know what tstat you have are what units you have there. Might check out O and B that should be for the R/V valve. Also look on the blower door should be a wire schematic.
Post back in this same post with more info

ED

 

The thermostat is a Seco TA 2000. Only way I can get heat is for the aux. heater to be on. The reversing valve is energized with 24 volts when it's in heat mode, not cooling mode as you said it should be. When the aux. heat goes off, the voltage goes away and the valve switches to air cond. mode.

Now for the wiring.

The terminals at the Tstat are O, W2, X, R, Y, G, and E. Wires at the defrost panel are B, R, Y, D, C, and C. Wires at the furnace are W/Bk, G/Bk, R, Pr and Br. Schematic at furnace only shows wires leaving, but no interconnection with Tstat or defrost board in outdoor unit. I've traced all wires and think this is how it's wired. W/Bk from furnace goes to W2 on Tstat and B at defrost board. G/Bk from furnace goes to G on Tstat. R from furnace goes to both R on Tstat and R on defrost board. Pr on furnace is jumpered to W/Bk on furnace. Br from furnace goes to X on Tstat and C on defrost board. Y on Tstat goes to Y on defrost board. O on Tstat goes to D on defrost board. W2 and E jumpered on Tstat. The reversing valve is connected to 2 terminals on the defrost board where I've measured voltages. I'm sure I've confused you now, but appreciate the help.

 

Maybe the fact that the reversing valve is energized to heat instead of cool is a clue that it's wired up wrong. I intentionally turned the Tstat up high enough to turn on the aux. heat so I could measure the voltage at the reversing valve and got 24 volts. When I back Tstat off a little so that it's only calling for heat pump, the voltage went to zero and the unit switched to air cond., blowing 50 degree air through the registers.

 

You seem to be with it here so. "Think" some time back the R/V valves would work for heat only and always be in AC mode. Then they came up with you need heat more than the AC so for the R/V valve to fail it should fail in heat mode. So you have and old unit here now I think. And you need power to the valve in heat. I cant say from here what wires but Ill bet its in the O or B wire. O is for the cooling change over and B is for the heating change over relay. Try this on the tstat. R is power , C -X Common, G is fan, B is heat valve ,O is cool valve, Y is compressor W2 AUX.

Id say play with it. Some times I get mad at a wire setup and cut it all out and start all overand think it out.

Ed

 

Thanks Ed. Unit is in South Carolina so maybe they figured that it should fail safe in A/C mode. Think it was made in year 2000. I'm not there now, but I'll play with it some more next time I go down. Your explanation of terminals at the Tstat should help.

 

Rheem and Ruud still use B for the reversing valve energized in heat.

On the thermostat there might be a switch that switches O and B.

Thermostat=Furnace=Outdoor unit

R=Red=Red
G=G/Black
B=___=Blue
C=Brown=Brown
Y=___=Yellow
W2=Violet&W/Black=Violet

 

Thanks....your post just confirms what I had already figured out...B at the Tstat goes to the Violet (purple) at the outdoor unit and the W2 goes to B. Wires are obviously crossed as you said. I'm going back down in a couple of weeks and will reverse them. Just goes to show that units can be wired wrong when new and no one ever notices it. I even paid an inspector $200 to inspect this condo before I bought it and he gave the heating system a clean bill of health. Didn't take my wife long to figure out that it was blowing cold A/C air when the aux. heat shut off.

Thanks.