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Tankless boiler, Indirect DHW, Zone valve controller - How to wire the three for DHW priority

I have a completely new system I am trying to get wired properly.
The components involved are:

TT Prestige Solo 175 boiler
Smart 50 indirect DHW heater
Taco ZVC404-exp (two of these because I have 8 heating zones)
Taco Z100T2 zone valves (controlling 8 radiant heating zones, 4 up and 4 down)
Three Taco Circulating pumps (1 for boiler circuit, 1 for heating circuit, 1 for DHW circuit)
Honeywell two wire heating only thermostats (8, one per heating zone)

I have the piping set up so there is a circulation loop that feeds everything and zone valves handling the 8 heating zones and a circulation pump handling the DHW loop.

I have the heating working fine. A thermostat calls for heat, the boiler fires up, the heat circulation pump turns on, and the zone valve opens until the thermostat temperature is reached and then everything winds down.

I want to set up my DHW heater to be given priority over a heating call when the aquastat calls for heat.

How should I be connecting the SMART 50, TT boiler, and ZVC404-exp to have this happen? If I had only 7 radiant heating zones I could use the last (4th zone) on the master controller for the DHW and set the DIP switch on the ZVC to priority. But I have 8 zones so that fourth one is used already.

I see there is a Main XX and Priority XX location on the ZVC 404-exp board, is that what I should be using? If so how to the three things connect? What wires go where? Is there a DIP switch setting or configuration on the boiler I need to have?

Thank you for any help.

Comments

  • Zman
    Zman Member Posts: 7,125
    edited October 2021
    You want to control it within the boiler's controls. All 3 circulators get wired to, and are controlled by the boiler. The boiler will turn off the heat circ and turn on the DHW circ when you have a DHW call. You will need to spend a little time in the manual to get it configured correctly for the way you have it piped.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • nancyl
    nancyl Member Posts: 4
    edited October 2021
    Currently the boiler pump and the DHW pumps are connected to the boiler 110AC and the system pump is connected to the ZVC404 110AC. The boiler has a 110AC connection for CH pump, DHW pump, Pump 3, Pump 4. DHW pump is connected to the DHW slot, boiler circulation pump is connected to CH slot.

    Are you saying I should move the 110AC connection for the system pump from the ZVC to the boiler? if so, would that connect to Pump 3?

    Thank you for replying. :)
  • Zman
    Zman Member Posts: 7,125
    This is the most common piping arrangement. If yours is piped like this, it should be wired and configured this way.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • nancyl
    nancyl Member Posts: 4
    Thank you zman. I am piped this way but because I have 8 zone valves, not two, I think I need something to handle more than the boiler can control thus the Taco ZVC. That's where I have the wiring "disconnect". Make sense?
  • nancyl
    nancyl Member Posts: 4
    If there is anyone familiar with the Triangle tube prestige solo 175 configuration options, I could sure use some help.  Thank you all!
  • Zman
    Zman Member Posts: 7,125
    It doesn't matter if you have 2 zone valves or 100 zone valves. The control strategy is the same.
    Is the DHW circ tied to the boiler loop or the heating loop? Once all the circs are wired to the boiler, the configuration is really simple. Which circs do you want to turn on when heat calls and which do you want to turn on when DHW calls? The boiler really doesn't care, just go into the setup menu and tell it what you want it to do.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    MikeAmann