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Thread: Heat pump losing heat - please help

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  1. #1
    DIY Junior Member Joe Garfield's Avatar
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    Default Heat pump losing heat - please help

    I have an electric heat pump with electric coil emergency heat. The unit (Armstrong) was serviced about a month ago and checked out OK.

    The past week or so, I hear the fan running constantly, and every time I look at the thermostat, the unit is in Emergency mode. I have not been able to adjust the thermostat w/o it eventually clicking into Emergency.

    Concerned about the amount of electricity I have just wasted, I changed out the thermostat. Everything tests fine at first, but I am noticing that with the heat on, it starts warm and gets cold. The outside compressor kicks on and the outdoor fan runs. The thermostat makes the necessary 'clicks' and appears to be working properly. The fluid in the insulated line, between the house and the outside unit, starts getting warm, then gets cold. After a period of 30min, the house actually starts getting colder.

    I do not hear fluid rushing through the lines like I used to. It has been very cold outside over the past 2 weeks, but has been warm yesterday and today.

    The cooling function seems to work well - at least it starts getting pretty cold. I have not had the cooling section on for very long though.

    It is in the 60's outside today. The thermostat says 67F inside. I set the heat to 69F and it never goes above 67, but actually drops to 66.

    There are no signs of obvious damage or ice outside.

    Could it be a stuck reversing valve? Is there anything a homeowner can do to diagnose or fix this?

    Thanks for your help.

  2. #2
    Plumber jimbo's Avatar
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    When your temp is low 30's or below, the heat pump will not do much, but at 67 degree outside, that is primo operating range, so something is wrong.

    Diagosis of sealed systems is not amateur hour. At a minimum, you would need a set of gauges and a good digital thermometer to properly analyze your sub-cooling perfomance. This is the only true diagnostic for your system. But a good tech could interpret some of the more obvious symptoms. Yes, the reversing valve can be the problem. The fact that the small line from outside starts getting cool points to a problem. First thing you need to know, is YOUR system set up to energise the reversing valve for HEAT or COOL ?? ( on your thermostat, there should be a connection to a B terminal, or an O terminal) . A newer thermostat may just have one terminal, and a programmed set up determines how to handle the reversing valve. If you have a newer programmable, or even just digital, stat...get out the install book and check the set-up, after determining which system you have. I noticed you mention a newly installed stat, so that needs to be checked right away.


    Reversing valves can get stuck of course, but a more common failure is the coil, which is replaceable.

  3. #3
    DIY Junior Member Joe Garfield's Avatar
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    Thanks Jimbo.

    The system is energized in cooling mode (O) as opposed to (B). The thermostat was put in yesterday but the same issue has been going on for a few days > week. Luckily I was able to get a tech here on a Saturday evening. I sort of wish I didn't introduce the new thermostat variable, but it does seem to be working properly.

    UGH - apparently the coil is blocked - evaporator coil is warm at the top and cold on the bottom, both sides. He says it's an internal blockage, not repairable only replaceable. I asked if it could be removed and flushed and he said no. $1400 for labor to replace if it's under warranty, 'double' if it's not.

    Edit: Labor to install a new coil is $874. He said 'basically double that' for the cost of a new one, unless it's under warranty. I see them online for $230:
    http://www.alpinehomeair.com/viewcat...categoryID=493

    Is this something I can replace, or do most of the labor and have a plumber/friend do the connections? Sounds like a lot of cash. I cleaned the coil 2mos ago, does not seem very complicated to remove.
    Last edited by Joe Garfield; 03-09-2013 at 04:48 PM.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    When dealing with the coil, first thing that must be done is to purge the system of refrigerant. This must be recovered, there's a big fine if you just dump it into the atmosphere. A new coil needs to be brazed in place, with typically, a nitrogen bath of gas running in the line to prevent corrosion on the insides of the pipe. Then, a vacuum must be pulled on the system and new refrigerant (and maybe oil) introduced. This all requires some training and specialized tools. If it weren't for the requirement to safely recover the refrigerant, you could get things in place, ready to seal up and refill the system. Depending on the type of refrigerant in the system, that can be a very significant part of the cost.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    DIY Junior Member Joe Garfield's Avatar
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    Thanks Jim, I won't get involved in any of that.

    Does the symptom and diagnosis sound right (blockage in the coil leading to temperature differential across the coil)? Is it worth having someone else come out?

  6. #6
    DIY Junior Member Joe Garfield's Avatar
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    I am looking at the Armstrong literature and see the heat pump is equipped with a 'bi directional liquid line filter drier' - if I reverse the flow (run cold) and dislodge the blockage, shouldn't this be able to catch the blockage? I was told not to do this as the blockage could ruin something in the heat pump/compressor, which is more costly to repair.

    Thinking about this, I guess I don't know what side of the coil the filter is on, or which way things will flow when reversed. Is it worth a shot?

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