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3 zone Hydronic Heating; 1 Zone hotter than others

I'm wondering why my three zones have very different temps.
2500sq ft house.

Zone 1: Main Floor, one room on a slab, with about 16-20 ft worth of baseboard.
Zone 2: Upstairs, guessing 30-40 ft of baseboard (kids r sleeping, so can't measure it now).
Zone 3: Main Floor, rest of the house (28ft of baseboard plus a K120 kick heater rated at @11,000BTUs), plus the basement (probably 32 ft of baseboard).

Thermostat 1 for downstairs, and Thermostat 2 is upstairs. They currently hook up straight to the boiler, and call all zones. Note: each zone does have a honeywell control valve; but they are set to open. (These points will come in handy later).

Boiler is a Weil-McLain CG5, 140K BTUs.

Zone 3 is super hot, and works great.
Zone 1 and 2 are barely lukewarm.
If i shutoff Zone 3, with shutoff valves... Then Zone 1 and 2 heat up very nicely...yet, not enough to get my kick heater working (needs 120 degrees to turn on). The kick heater previously worked.

We are in middle of basement remodel, and we replaced the previous baseboards, added a couple more, and moved some pipes... But I didn't think we would have impacted the system that greatly.

So, any hints where the source of my problem is?
I feel like Zone 2 was always hotter, even before making basement changes.

Options I was thinking:
- Add a Taco ZVC404 and Let Tstat1 control ZOne 1 and 3, and Tstat 2 for ZOne 2? This still does not solve my kick heater.
- Add an additional circulator or some kind of pump to Zone 1?
- Remove some of the basement baseboards? (Not sure if adding the additional 8 feet (if i remember correctly) would be puling down the whole zone?)
- Is there some other plumbing issue?

Thanks, much in advance.


  • Big Ed_4
    Big Ed_4 Member Posts: 1,775
    Normal zone valve heating issue . The water flow is taking the least resistance . Once the least resistant zone is satisfied and the valve closes the next would get better .. What would help is repiping the zones on one side . Where the first to leave the boiler is the last to return .
    I have enough experience to know , that I dont know it all
  • shamu1023
    shamu1023 Member Posts: 8
    edited September 2020
    Thanks. If I get a Taco ZVC403 or ZVC404, can I connect Tstat1 to Zone 1 and 3? If so, how?

    Like this?
  • mattmia2
    mattmia2 Member Posts: 3,979
    Is all this stuff in zone 3 in series or parallel? If the kickspace heater is in series and at the end of a run it probably will never get particularly hot water. Is the kickspace heater on the zone that is heating well?

    You could wire the t-stats to control each zone valve directly if they have end switches and wire the end switches in parallel to tt on the boiler.
  • shamu1023
    shamu1023 Member Posts: 8
    The baseboard is all in series.
    The kick heater is in parallel... But, yes, it appears to be later in the run... but hard to tell as I can't see where all the pipes go, as they go inside the wall, and turn.
  • shamu1023
    shamu1023 Member Posts: 8
    @mattmia2 .
    REgarding end switches for wiring the zones. The Valves are 5 wire Honeywells. So, I think what you're saying is instead of wire jumping on the Tstat side of the Taco... I should wire the valve controls together, then connect to Zone 1, and Tstat 1 on the Taco.

    If I pull up wiring diagrams for the Honeywells, I can figure it out.
    PLease confirm.