Heat Pumps and Electric Heating - Rheem heat pump not switching to gas

Greetings,

I have a 12 year old Rheem heat pump furnace (Model #RGDG-075AUER), that is acting up. The blower runs non-stop during the night because the heat pump can't keep up with the colder temps (high teens, lower 20's), and the burner isn't firing off for backup heat. I changed out the thermocouple last week because the pilot light wouldn't stay lit (that fixed that problem). I performed a quick ops check by switching the thermostat to "emergency heat" and the burner fired off just fine. Well - now that I need the thing to do it on its own - it won't. The burner won't light off when I switch the thermostat to "emergency heat" now either. The heat pump keeps up just fine during the day - but at night it obviously needs an LP gas assist. I am a very mechanically inclined person - I just don't know a whole lot about furnaces.

Any suggestions?

cmcginnis,

this one is driving me nuts, to try to keep this in the sympliest (and please excuse my spelling,turkey overload) do you really have a heat pump hooked up to a gas fired system, or do you have a straight air to the gas furnace. define exactly what you have and we will try to give assist. i swear to goodness i'm not tying to talk down but a lot more infi\o is needed
barry

It could be that my terminology is wrong :o - so let me tell you what I think I have and maybe that will help. Outside my house is what I would normally call the compressor/evaporator/fan unit. I am calling that my "heat pump" (but only for the sake of producing heat - otherwise I would normally just call it an air conditioner. It is my understanding that when "heat" is selected on the thermostat in the house that the heat pump does the reverse of the A/C - in that it removes the "cold" from the air and therefore produces warm air. Maybe that is where I am confusing you (or maybe I'm just confused? :D ). What I do know is that the outside unit is the only thing that runs when the temperature is above the mid 20's (besides the fan in my furnace in the house). The only time the gas part of the "furnace" runs in the house is when the temperature gets down into the 20's and below (like in the middle of the night - or the middle of the winter :) ). It's like the gas portion is merely a backup to take over once the heat pump can't do its job anymore due to the temperature being too low. Does that make sense - or am I way off track?

What you have is a dual fuel system.

I would have said the fossil fuel kit (should be a box mounted to the outside unit with a dial and a switch in it) was messed up till you said it didn't work in Emergency either.

When in Emergency heat does the compressor shut off and the gas just not work or does the compressor continue to run?

Take a look inside the box (fossil fuel kit) outside and make sure the switch hasn't got flipped to heat pump only. also make sure that the dial is set at a reasonable temp (around 40 would be ok). you can turn the dial up and down and should hear a click when it switches.

If the compressor stops when you turn it on emergency heat see if the gas lits when the call for Aux heat is made. if so then the wiring is messed up.

Let us know.

Thanks for the replies.

What you said is definately what I have - a duel fuel system (I learned something new today!). I found the fossil fuel kit mounted on the side of my house, by the compressor unit, and I removed the cover. Inside the box I found a switch that was flipped to "both systems", not "heat pump only" - so that was good. The temperature dial was set at 30 degrees - and it was very stiff when I tried to move it. I moved the dial around a few times, and I set it back where it was (the dial did loosen up a bit after I moved it). I never did hear a sound when I moved the dial???? I tried it with the system on and off - still no audible sound??? I didn't see anything "obvious" in the box (like a broken or chewed through wire - and all the terminals seemed to be attached OK).

I also checked to see if the compressor stopped when I switched it to emergency heat - and the compressor did indeed stop when I switched it over - but here's the weird thing - after I switched it to emergency heat - I went downstairs to my furnace and the burner had fired off like it was supposed to! I thought that maybe we were on to something - but after I put the cover back on the fossil fuel box - I switched it to emergency heat again to see if everything was still working - and this time the burners wouldn't fire - no matter where I set the thermostat??????????? So now - do I have a bad fossil fuel temperature dial? Or maybe a bad thermostat?

I truly appreciate what you all are doing - and it appears that maybe we're really close.

BTW - Once I get this thing working correctly - should I change the setting on the fossil fuel box to a higher setting? Will it make that much difference?

When in Emergency heat the only things that matter are the thermostat and the furnace. everything else is out of the loop in Em Ht.

what kind of t-stat are you using?

What are the terminals used in it?

Does your unit have a standing pilot, or Hot surface ignitor?

So what you are saying is that the fossil fuel switch, and the heat pump itself are eliminated as potential parts of the problem. OK.

My thermostat is the original, standard, plain jane Rheem unit.

The terminals used are:

X = Brown wire
Y = Tan wire
G = Green wire
R = Red wire
B = Blue wire
E = White wire

The furnace has a standing pilot light that is working correctly.

I might add that I also have an Aprilaire humidifier installed on the furnace. Since I only use the humidifier in the winter months - could that play a part in the problem? I turned it on and off with the wall switch while I was doing my own troubleshooting - but that didn't change anything.

The temperature has dropped outside to the lower 20's and the temperature in my house was 60 degrees when I got home from work! The heat pump is not able to keep up, and the emergency heat refuses to fire off. I am trying to avoid calling a serviceman - but I will if I have to! Any ideas?

Something is deffinatly messed up somewhere.

Without being there I can't figure it out.

I say call a tech and get it fixed. Sounds like maybe a short in a wire or something somewhere. One of those problems that is hard to diagnose from afar.

Let us know what they find, and we can all learn something from it possibly.

I appreciate all your help anyway. Being that I am a tightwad do-it-yourselfer (I hate paying labor)- I am always willing to at least try.

Oh yeah - and it that wasn't enough - my 2000 Windstar wouldn't start this morning - it had a bad Idle Air Control valve - but at least I go it fixed. Things always seem to run in "threes" - so I wonder what will be next!

Thanks again!

Well - we have heat now. The heating & cooling guy came over today and fixed my furnace in about 20 minutes. It took him all of about 5 minutes to figure out what was wrong, 10 minutes to change out the part, and 5 minutes to write up the bill. It turns out that the problem was the pressure switch. The technician disconnected the two wires and installed a jumper wire. He then switched the unit on (to emergency power) and the darn thing fired right off! He also doubled checked to make sure that my vent fan had enough suction to activate the switch - and it had plenty - so he was convinced that the switch was the problem. He didn't have the right switch in the truck - so he had to get one from his shop. That took a lot longer than anything else. Once he got the switch permantly installed he ops checked it and so far so good!

I hope that maybe this might help someone else out in the future that experiences a similar problem.

Thanks for the help!