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HTP UFT not calling DHW pump?

old_maine_house
old_maine_house Member Posts: 4
edited October 14 in Domestic Hot Water

Hello-

I have a HTP UFT from ~2019 that isn't calling for DHW. Things I've checked:

In the status display mode:

  • (H:dh) It is correctly reading the indirect DHW tank temp as ~60 degrees.

In the installer mode:

  • 21:dh - Was at 130, changed to 140.
  • 22:dh - set to 5
  • 23:Pr - was at 1, set to 10
  • 24:Dp - was at 30, set to 0 (always DHW priority? I want that anyway).
  • 34:Ap, cP2:On - when I enable the DHW pump test mode I can feel the pump working and the pipes to (from) the indirect tank warm up a little
  • 39:sa - Set to SEns, which I believe is correct because I believe it's using the temp sensor coming out of the hot water storage tank.

When in normal operation mode:

  • No errors
  • CH calls and fires correctly
  • The DHW pump icon on the display never comes on, the DHW pump never runs, tank never warms up.

The system was installed by pros that seemingly knew what they were doing and has run fine for years.

I have had some trouble because some house painters got paint dust into the air intake and sporadically dealt with err 29, which the service company has fixed.

The service company was out here yesterday due to err 29 again and they said it was a bad ignition this time (though they got it running again for CH). It was unclear if they thought DHW was a problem or not.

Thoughts? I'm waiting on the service company but they are backed up today. Thanks.

Comments

  • LRCCBJ
    LRCCBJ Member Posts: 291

    Go to the CN7 terminal strip.

    Jump the two terminals with the black and yellow wires that read "DHW temperature sensor/aquastat"

    Report back.

    old_maine_house
  • Ironman
    Ironman Member Posts: 7,514

    I’ve had a couple of those where the board didn’t recognize a domestic call.

    Have the service company call HTP tech support to walk them through it and confirm it.

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    old_maine_housemattmia2
  • old_maine_house
    old_maine_house Member Posts: 4
    edited October 14

    >Jump the two terminals with the black and yellow wires that read "DHW temperature sensor/aquastat"

    When I do this, the display will flash err 32 - goes away when I remove my jumper.

    Edit: And measuring the resistance of the temp sensor wires appears to match the table: ~12800 for mid 60s degrees.

    mattmia2
  • LRCCBJ
    LRCCBJ Member Posts: 291

    Yes, that is normal if a sensor is installed.

    Disconnect the two wires from the sensor at the board.

    Go to installer parameter 39 and change it from sensor to aquastat.

    Restart the boiler.

    Jump the two terminals on the board again and see if the boiler will respond with a proper DHW call.

  • old_maine_house
    old_maine_house Member Posts: 4
    edited October 14

    When I change param 39 to aquastat, restart the boiler and jump the two terminals (with the temp sensor wires disconnected) I don't observe anything (related to DHW) happening on the display.

    Edited to clarify I don't see anything related to DHW (e.g. the DHW pump/circ icon) on the display. It's on.

  • mattmia2
    mattmia2 Member Posts: 10,754

    is the power button on the boiler turned on? There is an on/off button on the control panel on the left. If it is off it won't do anything.

  • old_maine_house
    old_maine_house Member Posts: 4

    Yes, I'm using only the display power button to turn on/off (not the hardwired "emergency" power cut off supplying main power to the unit).

    Yes, the unit was on for the scenario in my last comment.

  • LRCCBJ
    LRCCBJ Member Posts: 291
    edited October 14
    https://forum.heatinghelp.com/discussion/comment/1814246#Comment_1814246

    It does appear that the main board is not responding to a proper call from an "aquastat". Since the aquastat is just a switch, jumping the two terminals should immediately call for DHW.

    Give HTP a call but it does appear that the board needs replacement.

    Don't forget to return parameter 39 to "sensor".

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