Taco SR506 to Hydrostat 3250 Plus Constant Heat Call

BG9696

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!

GGross

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

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.

BG9696

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….

BG9696

"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

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.

109A_5

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.

109A_5

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

109A_5

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