Heat pump losing heat - please help

Discussion in 'HVAC Heating & Cooling' started by Joe Garfield, Mar 9, 2013.

  1. Joe Garfield

    Joe Garfield New Member

    Messages:
    10
    Location:
    Cincinnati Area
    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. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    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. Joe Garfield

    Joe Garfield New Member

    Messages:
    10
    Location:
    Cincinnati Area
    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/viewcategory.cfm?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: Mar 9, 2013
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,325
    Location:
    New England
    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.
  5. Joe Garfield

    Joe Garfield New Member

    Messages:
    10
    Location:
    Cincinnati Area
    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. Joe Garfield

    Joe Garfield New Member

    Messages:
    10
    Location:
    Cincinnati Area
    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?
  7. Joe Garfield

    Joe Garfield New Member

    Messages:
    10
    Location:
    Cincinnati Area
    Well, I found a company that does a 'free second opinion' - they came out, checked it all out and took some readings, and said the outdoor unit was low on fluid. Come to think of it, I am not sure if I remember the first guy even going outside.

    Luckily, I found out that the unit was installed in June of 2008, so it is still under 5yr parts and labor. It will be interesting to see who is right, and that will subsequently become my HVAC company.
  8. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    The filter is bi-directional because of course flow is reversed in a heat pump. A good way to check a filter is to simply check the temp at the inlet line and outlet line. Any difference of more than 2~3 degrees indicates blockage. The greater the delta T, the more significant the clog.
  9. Failure2Comply

    Failure2Comply New Member

    Messages:
    29
    Location:
    Virginia, USA

    If this is the case I would be calling his supervisor and file a formal complaint. Without putting gauges on and taking multiple temperature readings all he could do as guess, and that is not professional or acceptable. The refrigerant never goes bad, it only gets contaminated or it leaks out. IF your unit is low on refrigerant while it is still under warranty I would have them locate and repair the leak. If your unit uses R-22 the prices are high now but will scare you in a couple of years. Armstrong is owned by Lennox and Armstrong has been in business many, many years and has made some very good products in the past, that is why Lennox bought them. Also every time your unit goes into defrost the refrigerant flow is reversed. If there is a stoppage and it is the liquid line drier more than likely poor installation practices were employed during the install. Occasionally the factory messes up but not often. Let us know what this "Second Opinion" company says.
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,325
    Location:
    New England
    Failure to use dry nitrogen in the lines when brazing can release all sorts of crud on the inside of the piping from the brazing process.
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