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Taco SR506 to Hydrostat 3250 Plus Constant Heat Call

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BG9696
BG9696 Member Posts: 7
edited 4:16PM in Thermostats and Controls

System is indirect water heat, 5 zone hydronic w/Taco circs. I recently had a leaking valve replaced in my boiler system. After, the burner was failing to trigger. The HVAC guy mentioned he noticed the Hydstrostat 3250 temp control showed fluctuations in the temp and suggested replacing it which I did. This should be an on-demand system letting the boiler stay off until there's a call for either heat or hot water but now it's running the boiler at the set 180 deg high and trigger back on at approx 30 deg lower (155-160) bringing it back to 180, wasting oil which at the moment for obvious reasons, don't want to do. The Hydrostat continuously shows a dot bottom right of the current temp indicating a constant call for heat or hot water. I check/tightened all connections on the Taco SR506, turned off power and checked the removable relay "ice cubes" (all except the 120V one) and still shows call for heat. Turned off and physically removed all the basic Honeywell thermostats, still shows call for heat. After replacing the temp control unit for $230, I don't want to replace the Taco SR506 unless I'm sure this will cure the problem. Any & all suggestions would be greatly appreciated!

Comments

  • GGross
    GGross Member Posts: 1,885

    a pic of how you have the taco wired, and the hydrostat wired, might help. sounds like you have something wired wrong at the new hydrostat

  • 109A_5
    109A_5 Member Posts: 3,986

    Sounds like this is a new behavior since the Hydstrostat 3250 was changed.

    If all the heat demands are through the Taco SR506 and when the Taco SR506 has no active demand for heat yet the Hydstrostat 3250 acts like there is a demand for heat, I would suspect the wiring from the Taco SR506 to the Hydstrostat 3250 was inadvertently changed (or corrupted) causing the " indicating a constant call for heat or hot water ".

    I would completely inspect the wiring path between the Taco SR506 X - X terminals and the Hydstrostat 3250 T - T terminals. With the replacement work done maybe the two wires were crushed together somewhere.

    Also a test of the Hydstrostat 3250, with the power off, disconnect one of the Hydstrostat 3250 T - T wires then restore the power see it the call for heat has ceased.

    image.png

    image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    Alan (California Radiant) Forbes
  • BG9696
    BG9696 Member Posts: 7

    Thanks for the reply. I was very careful to replace each wire exactly as on the original Hydrostat. Pic of both the Hydrostat and Taco….

    Hydrostat.jpg Taco.jpg
  • BG9696
    BG9696 Member Posts: 7
    edited 5:36PM

    "Sounds like this is a new behavior since the Hydstrostat 3250 was changed."

    I'll try your recommendation though I was VERY careful with the replacement making sure each is correct and tight as was. I disconnected the ZC/ZR wires and this did turn off the call for heat dot on the Hydrostat. That wire goes to the Taco DR501 switching relay (indirect hot water) a separate unit from the Taco SR506 zone pane. On the SR506, zone 6 thermostat terminals are not connected to anything which I believe is that panel's indirect water thermostat.

  • 109A_5
    109A_5 Member Posts: 3,986

    In your picture ZC/ZR has no wires, just a jumper. The Taco SR506 X - X (Isolated End Switch) are the wires that go to the Hydstrostat 3250.

    Remove one or both of these wires, See if the call for heat goes a way.

    image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 3,986
    edited 6:29PM

    Bit confused with this " System is indirect water heat, 5 zone hydronic w/Taco circs. " so you have 5 indirect DHW (Domestic Hot Water) tanks ?

    Or 1 indirect DHW tank and 4 space heating zones.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 3,986

    Is this switch in the same position as the old unit ?

    image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 3,986

    No unintentional connection between these smaller Red and White (ZC/ZR) wires ?

    image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • BG9696
    BG9696 Member Posts: 7
    https://forum.heatinghelp.com/discussion/comment/1892940#Comment_1892940

    First, there are wires going to ZC/ZR but that's not what's circled in your picture. You circled TT terminals which I agree comes from the Taco SR506 terminals X/X. I disconnected 1 of the terminals (low voltage) live and it did not eliminate the call for heat dot on the Hydrostat. However, when I disconnected the 2 wires going to ZC/ZR on the Hydrostat, that did eliminate the dot. I believe those 2 wires control the indirect hot water Taco SR501 single zone control.

    In the Taco SR506 6 zone controller, there are no wires to the Zone 6 thermostat which is the priority thermostat used for indirect water. There's no wire from the lower section zone 6 for the circ pump either. There is a jumper between ZR/ZC.

    Near the indirect water storage tank is a Taco SR501. I'm wondering if the SR506 ZC/ZR is going only to the SR501, never touches the SR506 and the issue keeping the dot on is coming from the single zone SR501. ??

  • BG9696
    BG9696 Member Posts: 7
    https://forum.heatinghelp.com/discussion/comment/1892943#Comment_1892943

    Good question, the answer is no because for some reason, it was set for zone and not indirect though the house has indirect water heating. Should I switch it back to zone?

  • BG9696
    BG9696 Member Posts: 7
    https://forum.heatinghelp.com/discussion/comment/1892944#Comment_1892944

    I don't believe so. I replaced everything exactly as shown from the previous Hydrostat to this new one. It appears the Hydrostat is not the problem and I replaced it ($230) for nothing.

  • BG9696
    BG9696 Member Posts: 7
    edited 10:36PM

    Sorry

    https://forum.heatinghelp.com/discussion/comment/1892941#Comment_1892941

    Sorry if this was not clear. System has 5 heating zones (5 circ pumps) and 1 indirect heating zone w/storage tank. Per my separate post, the indirect heating has a separate Taco SR501 single zone control which I'm not sure if it is connected at all to the multi-zone SR506. The reason I don't think it is, because the SR506 Zone 6 (Priority Zone for indirect hot water) has no wire(s) on top in the thermostat section or down below in the circ pump section. Could the Hydrostat dot (constant call for heat) be coming from the single zone SR501 since after removing the ZC/ZR wires, the dot disappears?

    Turns out the SR501 single zone hot water has it's own power switch. When I turn that off, the Hydrostat dot turns off leading me toward the indirect hot water SR501 or hot water storage tank thermostat. On the SR501, I removed the R and W wires. Reading online that if the red line turns off after removing those wires, it's likely the thermostat which is a Residio L 4080 B 1352 that continuously is calling for hot water. Any ideas how to troubleshoot the thermostat?

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