Latest Discussions : HVAC


05:29AM | 10/22/98
I turned on our heat pump last night to take some of the nip out of the air in the house. This is my first experience with these things but it didn't really seem to help (yes, it was on heat not cool). In fact, the first time I turned it on it was actually cooling the house. I waited a little while, switched from normal to emergency heat and that didn't seem to do help either (at least it wasn't cooling the house). Am I doing something wrong? Does it take a while for them to start heating? Is there some other switch I need to throw? Any advice would be appreciated. It's a Trane XE800 if that helps. Thanks.


01:47PM | 10/26/98

I guess this is your first winter with a heat pump. Your description does not sound unlike my first experience. I’ll share with you what I learned. BTW – you did not say if the unit is brand new or not:

For one, the air coming out of a heat-pump register is only about 110 degree’s, sometimes less. That contrasts to the 180+ degrees found in an oil-fired or gas-fired unit. What I did was go out and purchase a meat thermometer, one of those units with a long, thin probe. Then, I inserted it into the exhaust side of the heater. If you have the unit mounted in the basement, usually there is a vibration damper, which is a black neoprene coupler that helps isolate the unit’s vibration from emulating throughout the house. I just stuck it through the neoprene, and left it there. This allows me to monitor the temperature of the unit.

If you’re getting temperatures somewhat less than 110 degrees, your unit probably is not functioning correctly. Next, I would make sure all of the circuits are fully on. You may find a breaker/fuse set at the main panel, on the inside unit itself, and also where the wires come out of the house and go into the compressor (the fan unit somewhere outside). If your home is geothermal, then this unit will albeit found in the basement/utility room.

If you are truly having trouble, and you have an outside part of the system, check to see that the unit outside is running (fan blades spinning). If not, the circuit may be off, tripped, or there is some other fault. I will point out, however, that many of the newer units have computer-controlled circuits, and mine, for example, would take awhile, sometimes up to an hour, to cycle into heat mode at the beginning of the season, going from cool mode. The units are really meant to be left on all the time. By this I mean the thermostat is switched to heat, not off, and not necessarily running. These units are constantly monitoring inside and outside temperature, and use this information to determine optimal efficiency. Since you just turned the unit on, it may need the cycle for 24 hours before fully operational.

However, you did mention that the air was coming out of the vents, albeit not warm. If your unit has an AUTO/ON switch, switch it to AUTO. This means that the air will only come out of the vents when the heater is actually on, meaning that when air is coming out, the heater thinks it needs to warm up the house. If at that moment the air is still cold, you probably do have a problem. I would run the unit for a couple of hours to see what happens. You will also need to get used to leaving it on all the time, and not really changing the temperature. If you try to raise and lower the temperature to save money, your bill will actually go up. The heat pump motto is: “Set it and forget it”.

Also, if it continues to remain cold, check your thermostat for blinking lights or some sort of error code. This may not be apparent right away, but may appear after a couple-hour’s running.

Possible problems that fit your symptoms:

Loss of Freon. Has happened to me many times. Usually the compressor (outside unit) will not be running because there is a safety device to keep the compressor from destroying itself because of no Freon.

De-ice sensor goes out. Usually the compressor is running, but the outside unit turns into a block of ice. This sensor is supposed to sense the ice buildup, then go into defrost mode.

Batteries in thermostat are dead or dying. If you have them, replace them. My heater when wacky when the batteries were down, even thought the thermostat’s display looked fine.

I should point out, though, that my system was plagued with problems primarily because the owner before me neglected the unit. As a result, the outside unit was not level, as it should be, then the fan lost one of its balance weights. Essentially, it shook itself apart.

As a final note, I found that getting a service contract with a yearly checkup was very cost-effective. Now, however, we own a new home, which is heated with oil. After 8 years with a heat pump, every time this heater lights off, the whole family starts stripping down to underwear because we just are not used to real heat.

Hope this helps - TomR


04:12PM | 10/26/98
Thanks a lot for the information, that really helped out. I'm sure the solution to my problem is in your response somewhere. Luckily it warmed back up so we don't have to worry about it for the next 5 days at least. Luckier still, our primary source of heat is hot water (I'm not really familiar with that either) so when it gets really cold we'll be fine. 110 degree air? I don't see the attraction of a heat pump. Thanks again.


12:41PM | 10/27/98

Glad to help. However, some of information you offered in your reply changes much of what I wrote.

You mentioned that water is the primary source for your heat pump. This means that you have a version of a geothermal system, which means also that you probably do not have an outside unit with fan. A little explanation may help.

All heat pumps operate by extracting heat from some outside source, and essentially releasing the heat into the inside of the house. The details are a little more complex, but I think you’ll get the basic idea. The is the same concept as an air conditioner, which does not really cool the air, but extracts the heat from the inside of the house and vents it outside. In fact, with a heat pump, going from a/c to heat is just a matter of changing the direction of the flow of freon.

The more common and least expensive system is the air exchange method, which essentially (in heat mode) gets its heat source from the outside air. I know it seems hard to believe, but the process of compressing and expanding the freon will extract heat even down to about 38 degrees with relative efficiency. When it drops below that temperature or you suddenly turn up the heat inside more than a couple of degrees, the heat pump goes into what I call “toaster mode”. This is when supplemental heat kicks in, in the form of resistance coils, which heat the air exactly like a toaster. These coils are also what come on when you flip into emergency heat mode. The air comes out of the vents pretty warm, but you’ll pay for it when the bill comes.

I should also add that there are other options your system may have, rather than resistance heat for the backup. These include an oil or gas-fired system. In this case the burner only lights when the heat needed or demanded exceeds the system’s ability to provide. I really do not know, however, what geothermal systems like yours use. It would be pretty obvious if you find a gas line running to the system, or have an oil tank.

Which gets me back to your geothermal unit. Yours works like the air exchange units, except you extract heat from water, usually via a circulating well arrangement. Coolant running in a closed tube loop is interchanged with the well water. Ground-source water usually is a constant 58 or so degrees year-round, which is perfect for heating or cooling. As an FYI, another type of geothermal system employs simply the coolant tubes buried in the ground, exchanging energy with the earth.

All this means is that everything I said in the original post about the fan unit outside does not apply to your system. I’m not totally up on geothermal, but your problem may be because the pump that circulates the water from underground may not be working for some reason (circuit turned off, etc.), and maybe the backup system in your unit only works when in “emergency” mode. You might try searching the net for your model number…might prove worthwhile.

As a final note, I really did not mind having a heat pump. Mine was of the common air-exchange variety, and although small for the size of the home, it performed adequately, even with all the problems. The big drawback is that they only have an average lifespan of 10-12 years, although that’s improving, I’m sure. Most of my problems were because of neglect by the previous owner, which is caused by people not being properly educated. If I were to get another one, something like yours would be my choice. It is supposed to be the best of the heat pump systems.

If it’s any consolation, I am not an HVAC contractor. I’m just another DIY trying to understand my world.

Good luck - TomR

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