Heat pump/ furnace question

[Code54]

I just bought a home and it has both a heat pump and a furnace (electric for both) and having never own or even been around a heat pump I am a bit lost. I have notice the heat pump does not “keep up” with the cold when it gets around 30 or less so I flipped the thermostat to “Emergency” and it seems to run the furnace. The settings on the thermostat are “Heat, Cool, off, and Emergency”. Am I running this thing right or am I missing something. The heat pump and furnace were installed last year but the old owner never left any books, receipts and there is no sticker even on the units as to who installed it ) I know she didn’t – this is what they call a “fixer upper house” /forums/images/graemlins/shocked.gif
Anyway any info would be great and sorry for the dumb questions but this heat pump and electric heat is all new to me.
THANKS

 

[Bird]

/forums/images/graemlins/laugh.gifScott, I, too, bought a house a couple of months ago with a heat pump. And I have a Robertshaw 9620 thermostat with "Cool - Off - Heat - EM" positions on the switch, and can't really say I understand that "emergency" position, but I found a 14 page manual for this thermostat on the Internet and printed it out. So the best I can figure, you're probably doing it right. The wiring diagram shows a wire for the backup furnace if you have one, and shows to jumper a couple of other wires for the auxilliary heat if you don't have a separate furnace I think. And it says to turn the switch to "EM" if the heat pump is not keeping it warm enough.

Now of course with all this being new to me, I knew the heat pump also had some electric heating coils to boost the heating, but I'm guessing that I don't have a separate "furnace" and you do. And that's only a wild guess. Does your "furnace" have a separate blower motor, fan, etc.?

I got the manual for my thermostat and guess I need to try to find a manual for the heat pump itself.

 

[gator]

The emergency position is actually for if the outdoor unit (compressor or fan) goes bad in the winter. It will leave the outdoor unit off and will only run the air handler with the heat strips on, to provide "emergency heat".

 

[Bird]

Thanks, Wally.

 

[techman]

The electric normally comes on when the thermostat sees about 3 degrees drop from setpoint, indicating that the heat pump can not keep up. If the electric aux is not coming on, then there is a problem with the thermostat or associated wiring (assuming that the electric works fine in "Emergency" mode).

Bear in mind that even when the heat pump can't "keep up", the heat it IS generating is 2 or more time more efficient than the electric strip heaters. The electric backup should supplement the heat pump, not replace it, for maximum efficiency.

paul

 

[Code54]

Wow- thanks for all the info!
I guess I should not be leaving it in the Emer position huh?? I noticed my heat pump runs ALOT when it is in the normal heat position is that "normal" It shuts off for a few minutes then runs for a good while, the the cycle repeats. So if I leave it in the "heat" position the furnace should automaticly take over and run when the heat pump is not keeping up correct?
Bird - thanks for the info also and yes I do have a furn. and it does appear to have a blower built in it. I was looking at it yesterday trying to figure the whole thing out and try and find if I could turn the blower up on it. I must say I think I miss the simple gas furnance /forums/images/graemlins/grin.gif
Thanks again to everyone and I just want to make sure I am doing all this correct so I don't kill the darn thing!

 

[Bird]

Paul, now that's what the guy told me who checked out this unit for me, as far as how this unit works. But he didn't mention the "emergency" part of the thermostat switch. What Wally said makes sense to me, and of course I know you're right in what you just said. My question is, "Are there only the heat strips or auxilliary, such as mine has, or are there other heat pumps with a completely separate "furnace" working off the same thermostat, and using either a separate, or the same air handler?"

 

[techman]

The most common system is a heat pump with electric strips as the supplementary heat. You can also have a heat pump with a conventional furnace (oil, LP, NG, etc) as the backup. The latter is called a dual fuel system.

In a dual fuel system, the heat pump coil is normally after the furnace (this is done so that condensate from the A/C does not corrode the furnace's heat exchanger). In a electric backup heat pump, the electric heating elements are after the heat pump coil. This is a critical difference. The heat pump can operate with the electric heat at the same time, since the additional heat is added after the heat pump has warmed the air. In a dual fuel, if the heat pump ran with the furnace, the heated air from the furnace would be warming the heat pump coil. This would cause unusually high pressures in the heat pump and possible system damage.

In a dual fuel system, the heat pump usually has a "fossil fuel kit". This is a control that will shut down the heat pump and run the furnace only when the thermostat calls for additional heat (called second stage heat). Some high end thermostats, such as the Honeywell VisionPro, can control a dual fuel system as well.

Dual fuel systems are popular where electric costs are high and other fuels are available (of course the rules all changed this year due to fuel prices).

paul

 

[gator]

I'll try to do a little explaining about heat pumps (trying to recall my college courses and job I had when I use to install them). Heat pumps are typically 2 types, split system and package. Split system is what MOST houses have, an outdoor unit (like name implies, located outside) and an air handler (ususally located in closet, attic or under house). The outdoor unit has a compressor, fan, coils and reversing valve (thats what makes it a heat pump vice air conditioner). The air handler has coil, fan, and in most cases, heat strips (yes we installed heat pumps without heat strips in them when customer insisted). Package units are all in one units and usually are outside or on roof and have ducts that run into and out from the house.
Most people don't realize that a heat pump puts out warmer than room temp air, but cooler than body temp air, so a lot of times they don't think its heating, cause it "feels cool". Most of these people are used to the heat output of gas or electric furnaces.
The heat strips (aka auxillary heat) are used on three occasions (depending on electronics in outdoor unit). Purpose number one is to heat the air when the heat pump is heating and goes into defrost mode (which is actually air conditioning mode, to use the hot freon to melt ice on outdoor coils), the second use is to augment the outdoor unit (again depending on outdoor unit electronics and proper thermostat connections), when the outdoor temp drops below the outdoor set point, which is when the heat pump cannot produce enough heat to make up for interior heat loss. The third function is for what I mentioned in my previous post (emergency heat).
Hope this gives you a better understanding of heat pumps.
Frequent long running of heat pump may be normal for your house, which depends on how tight and insulated your house is.
Edit: Dang, me and techman were typing at the same time but he finished before me!

 

[mjarrels]

I have a trane weathertron heat pump. Blue lite (Electric)comes on at very cold temps less then about 10 degrees. Emerg heat is for actual heat pump failure and is not to be uesd at any other time. My heat pump will run all night long at 20 degrees and never get the houe warmer than 66 degrees but I never see a blue light (big power bill).