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  1. #1

    Heat pump blowing cold air than needing aux heat to warm up

    A couple of months ago i had to replace my heat pump and air handler

    this is what i put

    heat pump - carrier 25HCC536
    AIR HANDLER - carrier fv4cnf005

    Anyways recently its been cold and i have the thermostat at 70 and when it starts it blows cold air lowering the temp of the upper floor and then when it reaches 68, on the thermostat it shows aux heat and finally it starts blowing hot air and warming the upper floor.

    Called the company that installed it and they look at the gauges and connections and the technician said that he didnt see anything wrong that if would happen again to change the thermostat, could it be really this?

  2. #2
    Join Date
    Jul 2006
    Did your tech explain the operation of your equipment?
    Cooling, Heating, what to expect in defrost?

  3. #3
    Quote Originally Posted by rickboggs View Post
    Did your tech explain the operation of your equipment?
    Cooling, Heating, what to expect in defrost?
    no he didnt, but i when i bought this equipment, they told me it was good and that it would heat and cool the house better than what i previously had..

    additionally my thermostat is a luxpro DH2110 if this helps, its a plain cheap thermostat

  4. #4
    Join Date
    Jul 2006
    No new tstat with new equipment?

  5. #5
    no, they left the old one i had

  6. #6
    any one have any ideas or been having similar issues? if it is the thermostat i might attempt replacing it myself

  7. #7
    Join Date
    Nov 2008
    I'm not a pro, but I can attempt to help you. If it's really cold outside (maybe below 30 degrees) the heat pumps have trouble keeping up with the demand for heat. Normally, that's when the auxillary heat would kick in. I'm guessing that your auxillary heat are electric coils in the Air Handler. I'm really surprised that the installer sold you a new system without a new thermostat. I'm guessing that the switchover temperature is either built into the heatpump or the air handler. If the switchover temperature is wrong then I'm guessing that could cause the system to blow cold air because the heatpump can't keep up with the demand. I would still think the auxillary would kick in. I believe the auxillary uses part of the heating coils and the emergency uses all of the coils with no heat pump. I believe the emergency is for temperatures when it's not economical to use the heat pump.
    I agree with the other posters and say you need to get the installer back out to explain the operation. Ask them what the switchover temperature is for the auxillary heat. Ask them why they didn't install a new thermostat on a new system. In fact a good thermostat that they normally would install probably guarantees decent operation of the system with all of it's functionallity. If you install the thermostat on a new system yourself, you may void the warranty.
    Another thing to consider is sizing. If they oversized or undersize the new system I've heard that can have drastic effects on the heating and cooling ability. I'd ask the installer how he sized the new system (preferably a Manual J) and ask for the proof.
    The only other thing I can think of is that maybe they've miswired the system. I'm not a heating and cooling pro, but I am fascinated by the trade. I had a new system installed a couple of years ago and watched the 3 installers very closely. I didn't do this to be a pest. I just wanted to understand how it works. When the new thermostat didn't show the outside temperature I asked the company about it. They sent out a tech and I suggested that it was miswired. He didn't believe it at first. After checking everything else he discovered they had miswired it. Of course I checked that out first, but since it was still under warranty there was no since in me voiding the warranty. Good luck.
    Last edited by beenthere; 02-13-2011 at 05:53 AM. Reason: price

  8. #8
    i think a thermostat with an outdoor air sensor would help you alot if you are sure the unit is working correctly. i dont know your location but if you are in a very cold region. it probably takes some time before the aux kicks in where if you get a thermostat with outdoor air sensor you can program it to kick in aux at start up.

  9. #9
    i was researching and thats what i see that its to cold outside and the heat pump cant keep up with it under stage 1, i dont have an outdoor sensor and and was planning on putting one but i assume there arent any wireless outdoor sensors that i could connect to a new thermostat that could assist me with this

  10. #10
    Join Date
    Nov 2007
    I'm having trouble understanding why, if the heat pump is running in heat, even if the aux heaters aren't running...why the room temp is actually dropping that quickly.
    It sounds like perhaps the heat pump is running in defrost and not turning the aux heaters on at the same time which all heat pumps should do.
    Defrost is nothing more then the unit switching back to a/c and will blow cold air into the house if the heaters aren't running.
    It sounds like this needs to be checked.
    I know heat pumps really struggle when the temp drops below lets say...35-40 degrees but for the house temp to drop...something aint right.

    UNLESS of course the house temp is dropping over a extended period of time (and not right away) and the heat pump just isnt keeping up, which again is why the aux heaters are necessary...

    I can't imagine you are in a very cold climate, otherwise you would be using fossil fuel to heat. Most of the time, outdoor lockout sensors to shut off the heat pump and run only the electric heaters are not used and not necessary. Running strictly electric heat is too costly...get what you can out of the heat'd be suprised how well it can heat even when its very cold out.
    HEAT PUMP HEAT IS "COLD HEAT" without the aux heaters running.
    YOu need a digital tstat that can monitor how long it's taking the system to satisfy and bring the aux heaters in accordingly. Honeywell 5000 is basic, simple to use, and very efficient at this. Even has a Economy/Comfort setting for you aux heaters...

  11. #11
    Join Date
    Sep 2002
    I don't know
    Most of what has been posted in this thread is bad info.

    Take sandpipertech's advice.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  12. #12
    Join Date
    Jul 2007
    I don't know if the search funtion is available to all, but the above post about incorrect information being posted is the first post that is correct.
    Always here

  13. #13
    Join Date
    Jan 2004
    Lancaster PA
    Many of the Luxpro thermostats need the indoor temp to drop 2 degrees or more before they will energize the aux heat. So a very good chance that it is your thermostat causing this problem.

    When you take notice to this happening. Is it on colder days/nights. As in below say 40 degrees outside?

    If so, ask your installing company to install a new thermostat that will bring on the aux heat quicker.
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    How many times must one fix something before it is fixed?

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