Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Wiring of Hydrostat 3250 plus with TACO ZVC404 zone control box

Hello. I had new "cold start" furnace installed 3 days ago with the Hydrostat.

Instead for wiring as indicated in Diagram 5 on Page 5 of the Hydrostat manual, contractor wired to C1 with NO wiring to ZC or ZR. He also set High Temp and Low Temp limits to identical limit of 160 degrees for both. Because the furnace is "cold start," shouldn't the Low Temp limit be turned "OFF?" Also, shouldn't Jumper B be removed per the manual? With this wiring the Economy Active Light is not lit on the outside of box so is the Thermal Targeting working?

Lastly, it seems the TACO box is designed to have thermostat wires go in the top and have thermostat wires come out the bottom, but he has the circulator wires cross the inside of the box and come out the top where the thermostat wires come in. I know wires are low voltage, but heat still generated; won't wires become brittle over time being in the box, or am I making something out of nothing?

The installer is coming back tomorrow to address my questions, but the salesman who I called to ask about issues, states the Hydrostat can be wired many different ways, I explained I simply want it wired the correct way.

Please help. Thank you


  • DJD775
    DJD775 Member Posts: 224
    edited October 2022
    Maybe a better description of your system will help. Do you have an indirect water heater attached to the boiler? How is the wiring connected now?
    The low and high limit set at the same number is not right and definitely not cold start.
    I wouldn't be too concerned about the low voltage wiring in the control panel.
  • timmichalak48
    timmichalak48 Member Posts: 2
    An indirect 40 gallon Superstor Ultra is part of system. There is a red wire on the C1 terminal in the Hydrastat, red and white wires on the TT terminal, black and white on L1 & L2, and black and white on B1 and B2. There is no wire on ZR to the TACO zone box which Diagram 5, page 5 on the Hydrastat manual calls for. I believe the ZR would override the heating zones to assign priority to the the hot water

    I appreciate any help. Thank you.
  • DJD775
    DJD775 Member Posts: 224
    edited October 2022
    Not sure what the C1 is wired to but they might have it wired to the zone control panel to hold off the circulators if below the low limit or if the 120f circulator hold off function is activated. If you want it to be cold start, set it up as in diagram 5. The wire to ZR on the aquastat is to tell the boiler to override the economizer limit and fire to the high limit if there is a call for domestic hot water.