New York HP Controls Question

Discussion in 'Maintenance and Troubleshooting' started by SyracuseGeo, May 5, 2015.

  1. SyracuseGeo

    SyracuseGeo New Member

    This should be a fairly simple controls issue, but fixing it is driving me crazy. I have a 4 ton 2-stage Daikin heat pump (works great) and an Ecobee Smart (the old version) thermostat. I'm very pleased with the performance of both, but I'm having trouble with the changeover from heating to cooling and vice-versa.

    The Daikin/McQuay HP uses 4 wires to control the compressor: W1, W2, Y1, Y2.
    The Ecobee Stat uses 3 wires to control the compressor Y1, Y2, O.

    Daikin
    R- Thermostat Power
    Y1 - Cool Stage 1
    Y2 - Cool Stage 2
    W1 - Heat Stage 1
    W2 - Heat Stage 2
    G - Fan On/Off

    Ecobee:
    R- Thermostat Power
    Y1 - Heat/Cool Stage 1
    Y2 - Heat/Cool Stage 2
    G - Fan On/Off
    O - Heat Pump Reversing Valve (controls on/off operation of the heat pump), energized in cooling

    I tried installing a SPDT relay to resolve this issue (I bought this one http://www.automationdirect.com/adc...81_-z-_782_-z-_783_-z-_784_Series)/782-2C-24A), but the relay does not throw when O is energized. I know that my wiring is correct because I can manually force the heat pump from heating mode to cooling mode by pressing the button on the relay. However, it does not throw on its own based on O being energized.

    Do you guys have any ideas on how to resolve this? Is there a relay with lower resistance typically used for this application? Thanks so much!
     
  2. dgbair

    dgbair Just a hobby Forum Leader

    A wiring diagram of how you have the SPDT relay hooked up would be helpful. (especially the wires going to the relay's coil) And specifically which relay did you buy? 781-1C-24A?
    Edit: oh, I just noticed on the link name, it's the 782-2C-24A model.

    Also, you might need to be concerned with back EMF... depending on the protection built into the t-stat. A simple MOV would fix that concern.
    http://www.progeny.co.uk/Back-EMF-Suppression.aspx
     
    Last edited: May 6, 2015
  3. SyracuseGeo

    SyracuseGeo New Member

    @dgbair Thanks! Here's a diagram of what I did. This is in SPST form, but it should be pretty much the same for SPDT.


    [​IMG]
     
  4. dgbair

    dgbair Just a hobby Forum Leader

    So I would assume you also have the 'O' wire running in parallel to the unit as well?

    Did you check the AC voltage across the V1/V2 terminals with cooling mode active?
     
  5. SyracuseGeo

    SyracuseGeo New Member

    @dgbair I'm not sure what you mean by having the O wire running in parallel to the unit. I ran the O wire back to ground on the unit, should I be running it back to the T-stat instead?

    I did check AC voltage across V1 and V2 but I don't recall what the reading was. I'll check later today.

    Thank you!!!
     
  6. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Does this unit also have auxiliary heat?
     
  7. SyracuseGeo

    SyracuseGeo New Member

    @AMI Contracting It does have electric aux heating, yes, and I did not include that in the wiring diagram or the list above. Is that relevant?

    EDIT: FYI, the tests I did were without aux heating engaged. It's not clear to me if aux heating is locked out at the unit level in cooling mode, but it is locked out at the thermostat level.
     
    Last edited: May 6, 2015
  8. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Well I had an end around in mind but that breaks the deal. Explain what you meant by "I ran the O wire back to ground on the equipment". It appears the O should go to the coil on relay (V2) and O on the PC board from tstat. I would connect V1 to common not ground even though they should b the same.
     
  9. dgbair

    dgbair Just a hobby Forum Leader

    upload_2015-5-6_20-49-32.png

    You still need to get the O line to the reversing valve.

    And yes, V1 to common.
     
  10. dgbair

    dgbair Just a hobby Forum Leader

    hmmm, Joe do you think he got it fixed?

    This got me thinking, I always manual downgrade my system to a 1 stage cooling during the summer via the t-stat setting.... but I could do a similar thing here with the reversing value signal and 'break' the Y2 wire with the relay... hence the unit would never see a Y2 call in cooling mode.
     
  11. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    true, but doing what you are doing saves you the trouble. out of curiosity why do you downgrade? is it for dehumidification purposes? because the justification is not in energy savings.
     
  12. dgbair

    dgbair Just a hobby Forum Leader

    yeah its for dehumidification purposes.
     
  13. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    then I like your plan, but there might be an advantage to extending the droop vs all or nothing, but you would have to change the settings between seasons.
    j
     
  14. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Lower the air flow to remove more water.

    Mark
     
  15. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    As Mark suggests, slowing your blower will run the coil at a lower temperature which will pull more humidity out of the air. But it will not change the capacity significantly, thus satisfying the thermostat quickly, which then shuts the units off again. The best strategy for more dehumidification is to slow the blower down and increase the runtime through lower stage.
     

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