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GV90+ DWH thermostat leads

JamesP_VTJamesP_VT Member Posts: 5
I recently had a GV90+4 boiler installed, 4 zones with zone valves (zone 4 is DHW tank). System is using a taco zone controller (pretty sure it's a ZVC404-4). The controller does not have 2 boiler TT end switches (the ZVC404-EXP-4 does), so the contractor left the blue leads for DHW TT (page 58 of Weil-McClein manual) disconnected. Contractor suggested just turning efficiency knob all the way down when walking us through the system after installation, and I think this may be why. This leads me to 2 questions:
- How much efficiency (money) am I giving up by leaving the efficiency knob turned all the way down?
- Could I connect the DWH TT lines to the Zone4 circulator end switch (normally open) contacts? (There is no Zone4 circulator, so those contacts are unused.)


  • EdTheHeaterManEdTheHeaterMan Member Posts: 405
    edited January 14
    if you are using the boiler primary circulator as the circ for the DHW zone. then the priority for the DHW will need to be handled by the Taco ZVC. The DHW leads on the boiler is to operate a DHW Circulator at high boiler output. and the "Primary" system circ to operate at a lower temperature as the demand changes. You need the primary circulator and system to operate at high output for the DHW. The TACO ZVC can't tell the boiler the difference.

    This may also be the cause of the short cycling issue you described in your other post
  • Tom_133Tom_133 Member Posts: 670
    Where in Vt are you?
    Montpelier Vt
  • JamesP_VTJamesP_VT Member Posts: 5
    I'm in the Burlington area. I see you are in Montpelier. Weird winter so far, huh?
  • JamesP_VTJamesP_VT Member Posts: 5
    I think the taco zvc could tell the boiler the difference if I were able to connect the DHW TT lines. I was proposing using the zone4 circulator end switch since the control doesn't have a tt end switch separate for zone4. (I'm not using any of the circulator outputs of the zvc today.)
  • KennethGoetzKennethGoetz Member Posts: 3
    You have to use the two “blue wires” to now tell the boiler control to fire to 180 degree water to the indirect tank if so wired as a primary zone and piped according . Otherwise the control will adjust the boiler water temperature by its sensors to between 140 to 180 water temperatures per the set point in the control. This boiler control uses “adaptive learning”... Of boiler water temperature rather than an outdoor sensor
  • Tom_133Tom_133 Member Posts: 670
    Im in BTV all the time, if you want me to stop and give you a hand
    Montpelier Vt
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