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  1. #1
    Join Date
    Nov 2012
    Posts
    7

    Robertshaw 9620 Staging Aux Heat too soon

    We just purchased a house with a York 10 SEER heat pump being controlled by a Robertshaw 9620 thermostat. The whole system is about 11 years old. I don't think the thermostat is working properly. This week it has been about 40 - 50 degrees outside. I have the d1 temperature set to 1 degree and the d2 temperature set to 2 degrees. Current temperature setpoint is 68. The thermostat will bring on the heatpump when the temperature falls to 67 degrees (normal operation). Then after 5 - 10 minutes it goes straight to aux heat and stays in aux until the call is satisfied. The temperature on the stat never drops below 67. My understanding is that the heatpump should run 100% of the time (except defrost) until 1) the call has been satisfied or 2) the temperature falls to 66 and the aux heat needs to come on. I have tried setting the d2 temperature to 3 degrees and it behaves the same way. It also leaves the heat pump on while in aux heat. This is a dual fuel electric / gas system, should it be doing that?

    Thanks for the help.

  2. #2
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
    1,400
    First thing, You sure you don't have a heat pump with electric heat backup?

    If you have a dual fuel system that leaves the heat pump on while the gas heat is operational - That's is incorrect and will cause the heat pump to lock out on high pressure. If this is the case, you need to upgrade the thermostat to a setup with outdoor temp sensors and is dual fuel capable. I'm pretty sure that Robertshaw 9620 is not DF capable. There is nothing in the install manual about dual fuel. See attached link to manual below.

    https://pinnaclemil.propertysolution...e76e6b6560.pdf

  3. #3
    Join Date
    Nov 2012
    Posts
    7
    It is definitely dual fuel with gas. The indoor unit is a York diamond 80. I have noticed that the heatpump will go out on high pressure when the gas is running. I have a spare honeywell th6220 laying around. Should I just switch to that?

  4. #4
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
    1,400
    The honeywell 6000 is not designed for dual fuel either. The only way the HW6220 and your current thermostat will work is by installing a aftermarket relay pack to disable the heat pump when gas heat is energized.

    This thing has been running for 10+ yrs like this? Amazed the compressor hasn't blown up. The Honeywell vision pro IAQ and Nest 2nd Gen are just a few of the stats that will let your system perform to best of its ability.

    At this point, call a contractor, let them check out your setup. He can make sure you don't have a relay pack installed (but failed) or if you truly need a new thermostat setup.

  5. #5
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,145
    What I'm thinking happened is the previous owners may have just run it on "emergency heat" all the time. For thermostats I like the big blue WR stats or the ecobee. Everybody has their favorites though.

  6. #6
    Join Date
    Nov 2012
    Posts
    7
    So I just looked at the furnace and I have a dual fuel add on accessory. york 2ac02700701. This controller is supposed to cut the heat pump off when the gas heat is on. Is it possible that this board has gone bad? Also is it possible for the outdoor unit fan to run without the compressor running? I think my unit is doing this pretty frequently. It seems to run a lot (outdoor fan on) but the suction and vapor lines are both room temperature (seems to indicate the compressor is not running).

  7. #7
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,145
    Could be a bad board, but it could have be miswired. Duel fuel systems can be difficult, even for pro's. Get a pro that's familiar with dual fuel systems to come take a look at it. The outdoor unit should be OFF when the furnace is running.

  8. #8
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
    1,400
    Seems as if the relay pack/control board has failed somehow. Hopefully the compressor was not damaged because of this. Call a local contractor. Use the contractor locator map on this site.

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