I have a RUUD heat pump system. 8 years old. Recently the heat pump would not kick on, just blow cold air when the t-stat kisked on the heat. Found the problem to be the delay timer relay. It is bypassed at the moment till I get it replaced but all seems to be working fine. A week later now I have another problem. The heat kicks on and won't turn off. 4 nights ago it was 84 at 3AM and I turned the system off manually. I expected the problem to be in the t-stat so I replaced the old mechanical mercury filled one with a new programmable digital model from Hunter and it is made for heat pump systems. The problem is still occurring. And when it kicks on and stays, both the heat pump and the heat strips are on. Can anyone help me understand what is happening and what to look at?

 

Did you make sure the right wire is hooked up to the sub-base of the stat?

It maybe a relay in the unit itself that is tuck, causing it to do this.. I have not done many heat pump, so I couldn't help you much more.. I am sure Ed or HVAC will come around and help.

 

With the old tstat or new tstat did you try and take R off the tstat, would it turn off then? Pull the R+ off the transformer will it go off?? You can have a relay stuck on for sure. But dont sound right for the compressor to be on with the heater strips thats two relays. On the door of the unit see if you can find the wire schematic. On the old tstat when it stayed on where the strips on then also?the auxiliary heat is it on W2 on that hunter tstat? When it stays on The big copper line hot are cold? If you hit the inside unit hard with your hand on the side will it shut off?

post back and fill us in. In the same post.

ED

 

I did not try removing the R wire from the old tstat before replacing it. The time delay relay in the heat pump is jumpered on and all was fine for a week and now this problem arose. Yes when I had the old tstat and the unit stuck on then both the heat pump and the aux heat would be on and would stay on. at first I could move the tstat arm up and down and it would not cut off then some times I could get it to go off. Thats when I thought it may be the tstat and replaced it. Yes W2 is the aux heating. What big copper line? And which inside unit are you referring to? Tstat inside? Relays in the attic? Heat pump relays outside? The cold nights are coming!!!

 

Another note. I was mistaken on one thing now that you mentioned it earlier. The aux heat IS kicking on but the heat pump outside is not. Also, I disconnected the W2 wire (which also happens to be jumpered to the E terminal in the new tstat) and nothing changes. Another note is that when I click the tstat to OFF it shuts down and then when I move it back to ON it turns the aux heat back on regardless of the temp settings. This is true even with the W2 wire disconnected. Getting closer....

 

Did you Mark all the wires when you took the old tstat off? check out the wire set up here. If you jump R to G do you just get fan R to Y do you get compressor? R-G-Y to gether should give you heat . I think that the 4 way valve should fail in heat mode
If the compressor is on in heat that big copper line from the outdoor unit to the blower coil should be hot

ED

 

I did not actually "mark" the wires but I did take one wire at a time and move them from the old to the new tstat. I don't believe it will be the problem. I say that partly because the problem started before I replaced the tstat when I had the old analog mercury filled tstat. As for jumpering the terminals, when I jump R-G the fan comes on. Also when I jump the R-Y then heat pump outside does come on. Its unreal, sometimes when I move the tstat ABOVE the room temp the fan and aux heat will cut off and sometimes it will stay on. If I trust it to cut off when the room temp reaches the set temp then it will likely stick and will heat to mid 80's by 3AM when I awake in a good sweat. Any suggestions?