Rhode Island DeSuperheater operation/plumbing

Discussion in 'General Discussions' started by ChrisJ, Mar 4, 2017.

  1. ChrisJ

    ChrisJ Active Member Forum Leader

    My original heat pump was a combination unit. It made DHW on demand, so I have no experience with a desuperheater. The replacement unit is a water to air with desuperheater. I have looked at and shared Bergy's drawing many times.

    The main question I have is; When the DSH pump is running and the water is coming up the dip tube/cold water inlet, When it gets to the "T", Why doesn't the cold water, which is entering the "T" with household pressure behind it, dilute the recirculating water?
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    There is no cold water entering anything if there is no usage going on in the house.

    If there is hot water usage going on at the same time, you're heating the cold water.

    In summary, the btu always goes into the tank.
  3. arkie6

    arkie6 Active Member Forum Leader

    The incoming cold water will mix with the water from the tank only if there is water flowing out of a hot water spigot somewhere downstream. There is no flow in the incoming cold water line unless water is leaving the system. The DSH has supply and return to the same tank and has no net effect on the volume of water in the tank - what goes out = what goes in.
  4. ChrisJ

    ChrisJ Active Member Forum Leader

    Thanks guys!

    Now my problem is getting the DSH/HWG working. It's a ComfortAire with the DXM2 board. The not so knowlegable installer unplugged the black wire for the DSH pump. The schematic shows the wire going to the K2 relay but there are 2 blades on that relay. I am using the communicating tstat. The board in the heat pump is 90* counter clockwise of the schematic.

    Attached Files:

  5. arkie6

    arkie6 Active Member Forum Leader

    K2 relay Normally Open (NO) terminal should have a black (BLK) wire from your Compressor Contactor (CC) terminal T1. This is one leg of the 240 VAC supply to the HWG pump.
    K2 relay Common (COM) terminal should have a black (BLK) wire going to the the Hot Water Generator (HWG) pump.
    HWG pump should have two wires connected, the black wire from the K2 relay terminal COM, and a yellow (YEL) wire from Compressor Contactor (CC) terminal T2.

    The black and yellow wires provide 240 VAC to the HWG pump when the Compressor Contactor is energized and the K2 relay is energized. The K2 relay coil receives power via the control board based on temperature sensors on the hot water line.
  6. arkie6

    arkie6 Active Member Forum Leader

    Does your DXM2 board look like the photo below? If so, the black wire from the pump to the K2 relay should be plugged into the white circled terminal (COM). The black wire from the compressor contactor terminal T1 should be connected to the blue circled terminal (NO). No wires will be connected to the Normally Closed (NC) terminal (not circled on photo).

    Attached Files:

  7. ChrisJ

    ChrisJ Active Member Forum Leader

    Yes it's just like that and the wires are correct.

    Now on the S3 dip switches, all look like they are on in the picture. The manual doesn't describe what #1 is slave/master.

    #2 is test, #3 is 125*/150*, #4 is off/on
  8. ChrisJ

    ChrisJ Active Member Forum Leader

    Thanks Arkie6! It's working!!

    Next project is installing the SureStart from Hyper Engineering.
  9. ChrisJ

    ChrisJ Active Member Forum Leader

    The DSH pump is not turning it's self on even though the tstat says the compressor discharge temp is 150* and the EWT for the DSH is only 80*-90*.

    I take the lower panel off and touch the 4 dip switch little module and it clicks, I think the click is the K2 relay turning on the pump.

    I can then watch the EWT increase slowly on the tstat. Bad board?
    Last edited: Mar 11, 2017
  10. arkie6

    arkie6 Active Member Forum Leader

    Bad dip switch maybe or just a poor connection on one of the switches? You might try turning the power off to the unit and cycle the dip switches back and forth multiple times to wipe the contacts. Make sure the dip switches that are in the closed position are pressed firmly in the closed position.
  11. ChrisJ

    ChrisJ Active Member Forum Leader

    Threw the breaker for the unit and worked the little switches back and forth. Same issue.

    If I touch just the #2 switch it clicks the relay. That is the switch for normal/test. Manual says it should work normal even when in the test on position. I have tried leaving it in both positions. I will try leaving the temp setting on 125*, I have been trying it on the 150* setting because I added a mixing valve.

    Guess I have to look into getting a new board.
  12. arkie6

    arkie6 Active Member Forum Leader

    Dip switch #2 in the ON position just forces the HWG pump on for testing for up to 5 minutes. Dip switch #2 should normally be left in the OFF position to allow the DXM2 board logic to control HWG pump operation.

    I would check operation with Dip Switch package #3 (S3) with switches in the following positions and see how it works:

    S3.1 = ON (communicating thermostat = Master)
    S3.2 = OFF (Normal Mode)
    S3.3 = OFF (125F setpoint)
    S3.4 = ON (HWG enabled)

    Also, I would check using a voltmeter to make sure that your 24 VAC power supply to the control board is stable and within acceptable voltage range (18-31.5 V AC) during all modes of operation. If your 24 VAC supply transformer is faulty or not wired properly, the voltage may be dipping too low when there are multiple demands on the transformer. Try switching dip switch S3.2 to ON (HWG test mode) while monitoring the voltage supply to the DXM2 board. You can check supply voltage on the board from plug P1 (standard thermostat input plug), terminal 6 (R=+24 VAC) to terminal 7 (C=GND).

    If supply voltage is SAT and the HWG pump only works when dip switch S3.2 is ON, I would suspect a faulty HWG input thermistor or connection first before suspecting a faulty board. Check connections are tight and voltage present for termistors. Refer to manual here: http://www.climatemaster.com/geothe...g-guide-residential-geothermal-heat-pumps.pdf
  13. ChrisJ

    ChrisJ Active Member Forum Leader

    I have never used a voltmeter so I will get a lesson before I go poking around with that...

    It seems to be working, it's set to: on, off, on, on. It's been pretty cold in RI the last few days, so long run times. Check the numbers last night and had 115*F EWT for the DSH, climbing very slowly.
  14. ChrisJ

    ChrisJ Active Member Forum Leader

    The DSH hasn't been working consistently. The folks I got the heat pump from are not up on the latest digital versions(DXM2 board)

    My ground loop stays pretty cool for most of the summer so I don't think I will get much DSH warm water.

    I will look into the volt meter and testing voltages.
  15. Deuce

    Deuce Member

    Could it be that it is Spring and the unit isn't running as much?
  16. ChrisJ

    ChrisJ Active Member Forum Leader

    I don't think so, during a typical call for heat the heat pump runs long enough to get the compressor discharge temp up near 150*F.

    Manual says if the S3-2 dip switch is in the test position or the normal on position the DSH should turn on. I can slide the switch to test, it runs for 5 minutes then shuts off. I then slide it down to on and it runs till the HP shuts off. Doesn't usually turn it self back on during the next call, though I have checked it a couple times and it was running.

Share This Page