Heating ?

[FreightTrain]

I have a new house and I'm not sure if its just me or what but it seems like it takes a while for my heater to heat the house. It took 30 mins with the heater running non stop to raise my house temp 5 degrees, is this normal? I have a trane system with a heat pump. I know in the summer time it will cool the house a lot faster. So should I be concerned about this because my warranty runs out in a couple months.

[slow84lx]

I lived in a house with a heat pump for one winter about 10 years ago when they were just becoming popular in Georgia. The damn thing took forever to warm the house up and I was never really warm. The air temp coming out of the vents is much lower than the gas furnace air temp that I had been used to.

[FreightTrain]

Originally Posted by slow84lx

I lived in a house with a heat pump for one winter about 10 years ago when they were just becoming popular in Georgia. The damn thing took forever to warm the house up and I was never really warm. The air temp coming out of the vents is much lower than the gas furnace air temp that I had been used to.

Yeah thats the way I feel. I'm not liking it one bit, but these are suppose to be energy efficent. I don't see how when I freeze my ass off and the system runs for 30 mins at a time.

[Vertnut]

Originally Posted by FreightTrain

Yeah thats the way I feel. I'm not liking it one bit, but these are suppose to be energy efficent. I don't see how when I freeze my ass off and the system runs for 30 mins at a time.

Believe it or not, the heat pumps are pretty efficient, but they do blow a "cooler" heat.

[Big Studly]

what is the supply air temp. for a heat pump usually?

[Blue90LXSupercharged]

I have a heat pump works great. I also have auxiliary heater coils in the air handler for FAST heat. Do you have a digital controller? Try the emergency heat setting. That will kick in the afterburners lol.

[Doug Hatton]

I wasn't that knowledgeable on home HVAC so I paid attention at my recent home inspection. The house I'm buying has electric AC, an electric heat pump and a gas furnace. He told me that since the heat pump uses the outside air, it's only effective down to around 35 degrees outside. Once your temps get that low, the heat just won't get that warm. He told me to use the "emergency heat" which turns on the gas furnace in situations were it's too cold for the heat pump to work effectively.

[GARS04]

Originally Posted by Blue90LXSupercharged

I have a heat pump works great. I also have auxiliary heater coils in the air handler for FAST heat. Do you have a digital controller? Try the emergency heat setting. That will kick in the afterburners lol.

That's what I have. Im not posivitve but it seems like if it's 70 in the house and I turn it to 72 to just warm things up it takes a bit, but if I crank it to 76-78 it seems to take less time, I was thinking maybe it automatically turns on the emergency setting for quicker heat?? I dunno, I just know my electric bills are way cheap, all electric 1600 sq ft for about 110 a month... not a big house but I was paying more for a 1 bedroom apartment.

[Big Studly]

Originally Posted by Doug Hatton

I wasn't that knowledgeable on home HVAC so I paid attention at my recent home inspection. The house I'm buying has electric AC, an electric heat pump and a gas furnace. He told me that since the heat pump uses the outside air, it's only effective down to around 35 degrees outside. Once your temps get that low, the heat just won't get that warm. He told me to use the "emergency heat" which turns on the gas furnace in situations were it's too cold for the heat pump to work effectively.

if you are using 100% outside air all of the time, you are getting fucking robbed. That isn't the designation of a heat pump, that is an outside air economizer, and it should have a modulating damper with an enthalpy sensor to allow more outside air in when it is economical. A heat pump uses a typical refrigeration cycle for cooling and a reverse refrigeration cycle for heating....if I remember correctly from my thermo class a long time ago. Per ASHRAE, everyone should be using some outside air for indoor air quality purposes, but there is a minimum requirement, it should not under any circumstances be 100% outside air 100% of the time. If you don't have a modulating damper on the outside air, you need to have someone that knows what they are doing come and close it to about 25% of the total fan supply CFM which you can find on the name plate of the fan. You are wasting so much energy in the summer and winter, you would be shocked at how much lower your bills would be if you use 100% outside air now.

[Doug Hatton]

I never said it used 100% outside air. He was just saying that the outside air temps will make it less effective once the outside temps drop to around 35 degrees. Honestly, I haven't even moved in yet, but that's what he told me a few weeks ago at the inspection. You are correct in that is reverses the flow and pulls the heat off of the refrigeration process for heating.

[FreightTrain]

I do have a digital thermostat that has an emergency heat button. I guess I can try that out and see if it helps.

[Blue90LXSupercharged]

Originally Posted by FreightTrain

I do have a digital thermostat that has an emergency heat button. I guess I can try that out and see if it helps.

Cool. THat's what it's for, So you are o.k. Enjoy the heat

[Big Studly]

Originally Posted by Doug Hatton

I never said it used 100% outside air. He was just saying that the outside air temps will make it less effective once the outside temps drop to around 35 degrees. Honestly, I haven't even moved in yet, but that's what he told me a few weeks ago at the inspection. You are correct in that is reverses the flow and pulls the heat off of the refrigeration process for heating.

if 35 degree outside air makes the system work to hard, you either have an undersized unit, or too much outside air. at 25% outside air, the difference in mixed air temperature at 35F outside vs. 50F outside that would enter the heating coils is less than 4 degrees. That could be a lot of BTUH's with a lot of CFM, but in a home unit, I doubt it. At least nothing a heat pump shouldn't be able to handle.

[Doug Hatton]

Ok, then in a system that has an electric heat pump and a gas fired furnace, at what point is the furnace supposed to be used? IOW, the furnace is designed to be used as "emergency heat". When should it be used in a system that is operating correctly?

[silvercobra03]

Fireplace

[mikeb]

When I was growing up we had heat pumps and they sucked unless the "auxilliary heat" was on, and then the electric bill sucked. No win situation.

Gas heat FTW.

[bullet]

Originally Posted by Doug Hatton

Ok, then in a system that has an electric heat pump and a gas fired furnace, at what point is the furnace supposed to be used? IOW, the furnace is designed to be used as "emergency heat". When should it be used in a system that is operating correctly?

Are you sure your system has a gas furnance and a heat pump ? I have heard of some hybrids that have this but have not seen anyone who actually has one. A heat pump is good down to about 25-30 degrees. After that you have to use the auxillary heat strips by putting it in the emergency heat mode. The hybrids are suppose to have a gas furnace as backup instead of the electric heat strips from my understanding. Maybe some HVAC folks can better explain.

[Mark817]

I'll clarify...

A heat pump uses a normal cooling cycle but in reverse. The problem in cold ambient conditions (outside air temp) is that a compressor has to stay so hot to run and the refrigerant is expelling heat at the coil inside your house and transfering the cold to outside.

When the compressor outside gets to cold it reverses into a defrost mode, which basically puts it back in cooling mode. This will transfer heat outside instead of in to defrost the compressor. If the compressor freezes oil will migrate from the crank case and slug the compressor.

In regards to the mixed air damper set (outside air economizer) that is typical and common among commercial buildings and not so much of residentil. It either takes outside air or air from the return and cycles it through the coil and fan. It can modulate and take and percentage of outside or return air and it is always proportional. If outside air is at 30% then return is at 70%.

This is economic because when you are cooling in the house if it is 50 degrees outside you can take that 50 degree air and blow it through the fan vs your 70 degree air returning from the space.

As far as when and how that works you can do it strickly from outside temperature but an enthalapy sensor is best, it calculates humidity and temp for both outside air andreturn and which ever has the least enthalapy it uses. Enthalapy is on a 0-100 scale and it is defined as the amount of energy required to cool air.

Below 38 degrees a outside air damper is normaly disabled so that you don't freeze anything.

Minimum outside air is good practice but not a law. If you are not taking in a minimum amount of outside air and you get indoor air quality complaints you can be held liable. Typical buildings take in 10% outside air.

This is all typical of comercial buildings not residential.

Heat pumps are economical for our climate 80% of the time. They aren't good for really cold temps there fore they install emergency heat.

Emergency heat comes on when a heat pump is failing, in defrost or the precentage of error on the control is to high.

If you indoor temp is 70 and your set point is 72 the heat pump may come on at 1 degree below set point and your emergency heat may not come on until 3 degrees below setpoint. That is why setting the stat higher triggered you e-heat.

Hope that made sense.

[Doug Hatton]

The inspector that looked the place over said it had a gas furnace and an electric heat pump, and obviously electric ac so I'm assuming it's one of the "hybrids" you're talking about. I haven't had any personal experience with it yet, but should be moving in towards the end of this month. I'll post up my personal experience once I have some! haha....

Originally Posted by bullet

Are you sure your system has a gas furnance and a heat pump ? I have heard of some hybrids that have this but have not seen anyone who actually has one. A heat pump is good down to about 25-30 degrees. After that you have to use the auxillary heat strips by putting it in the emergency heat mode. The hybrids are suppose to have a gas furnace as backup instead of the electric heat strips from my understanding. Maybe some HVAC folks can better explain.

[Hunt4m3x]

Heatpumps are myths.

[turboskull]

Originally Posted by Mark817

I'll clarify...

A heat pump uses a normal cooling cycle but in reverse. The problem in cold ambient conditions (outside air temp) is that a compressor has to stay so hot to run and the refrigerant is expelling heat at the coil inside your house and transfering the cold to outside.

When the compressor outside gets to cold it reverses into a defrost mode, which basically puts it back in cooling mode. This will transfer heat outside instead of in to defrost the compressor. If the compressor freezes oil will migrate from the crank case and slug the compressor.

In regards to the mixed air damper set (outside air economizer) that is typical and common among commercial buildings and not so much of residentil. It either takes outside air or air from the return and cycles it through the coil and fan. It can modulate and take and percentage of outside or return air and it is always proportional. If outside air is at 30% then return is at 70%.

This is economic because when you are cooling in the house if it is 50 degrees outside you can take that 50 degree air and blow it through the fan vs your 70 degree air returning from the space.

As far as when and how that works you can do it strickly from outside temperature but an enthalapy sensor is best, it calculates humidity and temp for both outside air andreturn and which ever has the least enthalapy it uses. Enthalapy is on a 0-100 scale and it is defined as the amount of energy required to cool air.

Below 38 degrees a outside air damper is normaly disabled so that you don't freeze anything.

Minimum outside air is good practice but not a law. If you are not taking in a minimum amount of outside air and you get indoor air quality complaints you can be held liable. Typical buildings take in 10% outside air.

This is all typical of comercial buildings not residential.

Heat pumps are economical for our climate 80% of the time. They aren't good for really cold temps there fore they install emergency heat.

Emergency heat comes on when a heat pump is failing, in defrost or the precentage of error on the control is to high.

If you indoor temp is 70 and your set point is 72 the heat pump may come on at 1 degree below set point and your emergency heat may not come on until 3 degrees below setpoint. That is why setting the stat higher triggered you e-heat.

Hope that made sense.

Heat pump operation has nothing to do with the compressor getting "HOT"or the heat of compression,here is heat pump operation 101.#1 compressor compresses refrigerant,refrigerant is pumped out of comp.discharge line into reversing valve.#2 refrigerant is transferred to suction line via reversing valve,where it is pumped through evaporator coil,as it is pumped through the evap coil the high pressure gas turns back to a liquid(condenses) due to giving off its heat(you will see where the heat came from in a moment).#3 Liquid refrigerant is returned to outdoor condensor unit where it is fed through a metering device before entering the condensor coil.#4 refrigerant is transformed from a high pressure liquid to a low pressure liquid as it travels through the metering device.#5 Low pressure liquid begins to evaporate as it picks up heat from the ambient air,turning the low pressure refrigerant liquid into a low pressure gas where it returns to the compressor,it is compressed,and the cycle starts over again.To summarize this,a heat pump heats by removing heat from outside,even though outdoor ambient may only be 30 degrees,and bringing that heat into the house through a mechanical process,as heat moves from hot to cold.Modern heat pumps begin losing efficiency at around 20 degrees depending on humidity,therefore it is best to either install a outdoor thermostat locking out the heatpump @20 degrees, or manually switch over to emergency heat,hope this helps.

[428SCJ]

Originally Posted by FreightTrain

I do have a digital thermostat that has an emergency heat button. I guess I can try that out and see if it helps.

I made that mistake last winter (first winter in the house) F'n light bill went through the roof. Screw that switch LOL

Edit - it did get warmer faster but the electric bill was insane.

[UtHiNkUgOtMe]

You might want to make sure you have enough insulation...had an issue with the heat running forever. Had to add over 6" myself and no issues now.