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Wiring ALPHA 55 vs.Grundfoss 15-42

If I replace the Grundfoss15-42 with an ALPHA 55, can I wire it identically to the Honeywell anticipator unit?


  • J Van Lund
    J Van Lund Member Posts: 19
    More Info on Honeywell R8845U

    The Honeywell R8845U Switching Relay is wired to the UP15-42 so that when there is a call for heat it supplies 120 V AC.  When there is no call for heat, there is 0 V AC to the pump.  So the questions are: (1) Can the replacement ALPHA 15-55 be wired similarly so that there is no voltage to the pump when there is no call for heat?  (2)  Does the ALPHA 15-55 have to always be powered up to 120 V AC?  (3)  If not powered up all the time and cycles on and off, will there be any damage to the electronics in the ALPHA? See photo of Honeywell R8845U.  Power is from the bottom right on the TYCO transformer. then goes to the bottom left of the Switching Relay (Anticipator), and from the bottom right of the relay to the Grundfoss 15-42 single speed pump.  The system is 12 years old and has worked very well  If the 15-42 pump has to be replaced in the future, will the ALPHA be an improvement over the 15-42 and will the existing wiring work?
  • Weezbo
    Weezbo Member Posts: 6,232
    J ,

    i have never wired an alfa circ to turn off an on through a relay ,

    it has a design that does not require it to be .

    it slows down to almost a friction less type speed when there is no where for the fluid to go .

    while it is "on" it can sort of pick up the fact that a valve just opened. then if another opens as well it picks up a bit to meet it's need as well.

    turning it off and on with a relay is something i haven't had a reason to do.
  • SWEI
    SWEI Member Posts: 7,356
    Generally no need

    as mentioned above.  These new smart circs prefer constant power, which enables things like auto-exercise to work.  We even shut them off for the summer using their onboard menus rather than powering down.
  • J Van Lund
    J Van Lund Member Posts: 19
    ALPHA 55 with Electrically Controlled Zone Valves

    So with electrically controlled zone valves, the ALPHA will need to be wired the same as the "old" Grundfos 15-42, otherwise how will the ALPHA know when to start?  If wired this way, the ALPHA will be turned off when all zones are closed.  The only downside is the periodic exercise mode which is presently done in the off season by turning up the thermostat and running the system for 15 minutes every three weeks.  You have to be present to do this. Perhaps a surge protector would protect the electronics with power loss and power surges??
  • Zman
    Zman Member Posts: 7,553
    Either way

    Your alpha is designed so that it is OK to leave it powered on all the time. With most systems you can just plug it in, put in "auto adapt" and leave it alone. It senses that the zone valve has opened and does it's thing.

    If you prefer to turn it off and on, don't use "auto adapt" as it will reset itself every time it powers back on. If you switch it like your existing setup, it would be better to put the circulator in one of the "constant pressure" modes.

    There are tons of these things installed both ways. I think it is personal preference.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein