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Old 10-19-2009, 12:36 PM
 
Location: North Carolina
836 posts, read 1,200,195 times
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I have 2 heating zones in my 2 story house. There is a heat pump for the 2nd floor. When the thermostat turns on the, warm (not hot) air comes out of the vents. However, when the thermostat turns off, the air continues to blow out of the vent for 10-15 minutes and it feels much cooler. Is this normal? It's a new house and when I called about it I was told it's some sort of energy saving mode. Seems like a waste of electricity to have the furnace blow out cool air.
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Old 10-19-2009, 12:41 PM
 
Location: Las Flores, Orange County, CA
26,362 posts, read 55,867,493 times
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Quote:
Originally Posted by h2ohzrd View Post
I have 2 heating zones in my 2 story house. There is a heat pump for the 2nd floor. When the thermostat turns on the, warm (not hot) air comes out of the vents. However, when the thermostat turns off, the air continues to blow out of the vent for 10-15 minutes and it feels much cooler. Is this normal? It's a new house and when I called about it I was told it's some sort of energy saving mode. Seems like a waste of electricity to have the furnace blow out cool air.
My furnace (not heat pump) did that too. I think it is to gradually cool down whatever "element" was heating the air. If you shut off the fan and the heating "element" at the same time, then there would be no cool air flowing over it - may damage it. I think the idea is to turn the "element" off and let the fan cool it down for a few minutes.
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Old 10-19-2009, 03:12 PM
 
Location: Houston, Texas
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Charles is pretty much right. But I don't think your motor blows for 10 to 15 minutes as you say. It should run more like 30 seconds after you shut it off.
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Old 10-19-2009, 03:22 PM
 
Location: North Carolina
836 posts, read 1,200,195 times
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Yes, the blower does stay on for that long. And I too think it should only run for a few seconds after shut off.
Here's what I found at HowStuffWorks:
The heat produced by heat pumps isn't as intense as the heat produced by a gas or oil-burning furnace. Some people used to traditional furnaces are uncomfortable with the milder heat produced by these systems. Other people prefer the warmth produced by heat pumps, because heat pumps distribute heat evenly throughout the house, meaning there are no cold spots. A heat pump also should turn on and off less often than a gas furnace, and most systems have eliminated the blowing of cold air through the vents that used to occur when the system temporarily switched into reverse to defrost the coils.
Maybe thats my problem...I'm not used to it?
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Old 10-19-2009, 03:57 PM
 
Location: Somewhere in northern Alabama
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Heat pumps - these have a few quirks that newcomers to them don't expect. The basic AC in reverse works fine down to about 40 degrees outside, and then starts to get less efficient, which is overcome by some tricks.

When you have the thermostat on the heat pump in the heating mode, it doesn't just control the heat pump, but the auxiliary heat, which is either electrical heat strips in an enclosed box called an electric "furnace" or a gas fired furnace (usually propane). To overcome the "cold air coming out of the vents" stigma, once you crank the thermostat more than two or three degrees above the existing inside temperature, it also kicks on the auxiliary heat source. That negates a lot of the savings of using a heat pump, but it warms the air faster and makes people more happy.

Once the air is at temperature and the heater and pump shut off, the fan continues to run, so that the remaining heat in the electric furnace or around the firebox is used and the system is at a safe temperature. How long is that? Usually anywhere from half a minute to as long as ten minutes, depending on how the system was designed and set up. If the heat pump was only cranked a couple of degrees, the time between the pump and fan going off can be thirty seconds or even instantaneously.

In addition, heat pumps have to run in cooling mode every once in a while to defrost the outside coil and protect the unit. That means that there are times when you think you are getting heat from the heat pump, but it is actually working against the auxiliary heat source.

If the delay after a compressor shuts off is a measured fifteen minutes, and the air coming out of the vents is less than a couple degrees above room temp for more than a couple of minutes, the system likely needs adjusting or service.

FWIW, There is an ongoing debate about how to get the most efficiency out of a heat pump. Some people leave them on overnight to prevent the aux. heat from kicking in as much. What we do is turn the stat down to about 58 overnight, and when I get up I light a fire in the fireplace, use a propane wall heater, and bump the thermostat up two degrees, wait for it to go off, then bump it again, and so on. It isn't much of a chore and is done between other morning tasks.

Bottom line though, is if you bump a heat pump ten degrees or more you are going to be using the auxiliary heat source more than the heat pump, and your gas or power bill will go up.
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Old 10-19-2009, 03:57 PM
 
Location: Sanford, NC
635 posts, read 1,877,682 times
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Quote:
Originally Posted by h2ohzrd View Post
Yes, the blower does stay on for that long. And I too think it should only run for a few seconds after shut off.
Here's what I found at HowStuffWorks:
The heat produced by heat pumps isn't as intense as the heat produced by a gas or oil-burning furnace. Some people used to traditional furnaces are uncomfortable with the milder heat produced by these systems. Other people prefer the warmth produced by heat pumps, because heat pumps distribute heat evenly throughout the house, meaning there are no cold spots. A heat pump also should turn on and off less often than a gas furnace, and most systems have eliminated the blowing of cold air through the vents that used to occur when the system temporarily switched into reverse to defrost the coils.
Maybe thats my problem...I'm not used to it?
I can't comment on why your blower is running 10-15 minutes, although I tend to agree that seems like a particularly long time.

However, "HowStuffWorks" needs to update their info, or they are referring to another type of "heat pump" such as geothermal based units, or ground-source heat pumps. Those type of heat pumps use long coils or wells to circulate coolant underground, similar to a geothermal system, although there is a difference.

Most people in milder climates have the other type of "heat pump" which is basically a "reverse air conditioner".

But unless the "heat pump" is tied to a different type of heating system, such as hydronic, the delivery is the same as a traditional furnace, through forced air. And as such, the statement that "because heat pumps distribute heat evenly throughout the house, meaning there are no cold spots" makes no sense.

But it is true that heat pumps, particularly the "reverse air conditioning"(air source) type, do operate at lower temperatures. And at colder temps, typically below 20-30F, air source heat pumps do not work well at all and require electric heating strips or a secondary heat source. These heat strips are very inefficient and in colder climates can make heat pumps uneconomical to run. That is why this isn't a popular solution for colder climates where boilers and true furnaces still reign.

However, if one lives in a hot and humid climate, the other catch-22 for an air-source heat pump is that they can freeze up, and this is also where the heat strips come into play, to defrost the coils.

Heat pumps, which are a great technology solution, really are therefore best suited to "mild"(hot or cold) climates where the system can take advantage of the differential in outdoor/indoor temps but not be pushed beyond what is practical and economical.

Either way, none of this should be directly tied to your 10-15 minute run time per se, although there may be something else amiss or that is unknown and normal about your system.

Suffice to say, I would call your installer or local pro and ask them about the operation of the system to see if this is expected.

Good luck!
Al
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Old 10-19-2009, 05:21 PM
 
43,177 posts, read 47,049,205 times
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Why not google the brand name and get the model number then look for a FAQ section or manual on line.
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Old 01-18-2012, 08:20 PM
 
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the problem im having is the fan for my heatpump stays on. ive never seen a a/c do this. its a package unit and this weekend i had the service door off trying to figure out what was going on and it sucked the door out of my hand and when it slammed the fan turned off. it will stay off until i turn the heat on and when it cycles off the fan stays on. ive tried everything and dont want to start replacing parts when i have no clue whats going on. i have a digital thermostat. thinking it might be the thermostat, i removed it while the fan was running (even though i had it switched off and the heat wasnt on) and the fan still ran. the only way i can get it to stop is by killing the power to the unit. the fan just comes back on when i turn the power back on to the unit and will stay on for hours if i let it. if anyone has any idea on what the issue is, id be more then grateful. thanks
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Old 01-19-2012, 09:39 AM
 
Location: Johns Creek, GA
6,833 posts, read 21,956,687 times
Reputation: 5354
Quote:
Originally Posted by floyd86 View Post
the problem im having is the fan for my heatpump stays on. ive never seen a a/c do this. its a package unit and this weekend i had the service door off trying to figure out what was going on and it sucked the door out of my hand and when it slammed the fan turned off. it will stay off until i turn the heat on and when it cycles off the fan stays on. ive tried everything and dont want to start replacing parts when i have no clue whats going on. i have a digital thermostat. thinking it might be the thermostat, i removed it while the fan was running (even though i had it switched off and the heat wasnt on) and the fan still ran. the only way i can get it to stop is by killing the power to the unit. the fan just comes back on when i turn the power back on to the unit and will stay on for hours if i let it. if anyone has any idea on what the issue is, id be more then grateful. thanks

Strictly heat pump? Or do you have emergency backup source? Gas, or Electric?
Make and model?
T/sat make and model?

Info- when a service door is removed the unit is suppose to shutdown. There is a safety switch that disconnects power- sometimes they can stick if the panel hasn't been removed for a long time (hint). Probably why it shutdown when the panel was sucked outta your hand- it un-lodged the switch.
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Old 01-19-2012, 11:55 AM
 
Location: Somewhere in northern Alabama
11,748 posts, read 27,321,510 times
Reputation: 14561
"i had the service door off trying to figure out what was going on and it sucked the door out of my hand and when it slammed the fan turned off."

Consistent with contactor points getting pitted and sticking together as the metal fuses together under current load. The sudden jarring broke the metal bridge that had formed. There are other possibilities, but this would be the one to check first, and about the only one where getting a tech out wouldn't be a better course of action. The contactor can be replaced or, in some cases, the points filed to expose a good surface.
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