If you have a single pump and two zone valves for each thermostat the zone valve is stuck or set on manual.
If its a honeywell valve. Silver box. There is a little lever on the top of the valve. The slot that this lever moves in has a offset that will lock the valve in the open position. When this lever is locked into that slot it will keep the pump running so it will not shut off. Move the lever away from the locking side of the valve if its stuck on it.
If the lever moves freely back and fourth the thermostat is still calling for heat and may have a short in the wires.
Try turning the main shut off for a few min then turn back on to see if this corrects this issue.
What ever the issue is, it is simple to fix.
When raising and lowering temperature lower zone 1 and zone 2 valves, see photos, worked fine. Sorry but where is the shut off valve.
do you mean the emrgency shut off switch to the furnace?
The two valves, The ones with the black lettering on front and one that says 2nd floor.
These are the controls that turn on the zone in which heat is desired. When the thermostat calls, it opens up the valves and when the valve is almost open the pump begins to operate. The boiler is controlled by something else as far as turning on and off and has nothing to do with your issue.
The problem is one or two things.
1. The zone valve that services the area where your overheating is stuck on the open position, or 2. The zone is locked on and allowing hot water to flow without your ability to stop it.
The little lever on the valves that are just behind the wire connections is the manual control to bypass the operation of the zone. If you try to move this towards the lock grove in the slot and it moves easy, that zone is calling for heat. If there is resistance and you can not move it over then that zone is not calling for heat.
The first thing to check is the valve for the zone where your having the issue. If it can move over easy and the thermostat is NOT calling for heat, being turned all the way down below the room temp, then there is a short in the wires or the thermostat is faulty and not turning off.
If the little lever is stuck into the lock area of that little slot then your manually operating that valve and it needs to be released by simply pushing it further over and sideways to release it. Once released it should move on its own back to the closed position.
If that is not the case you want to rule out the thermostat first.
remove the cover on the thermostat, then using the red switch located next to the furnace shut that off. Listen to the zone valves carefully. put your hand on the little lever that moves freely and see if it is pushed back to the right side of the slot. If it does not move, the valve is faulty. If it does move proceed to next step.
While the boiler is off on the red switch, remove the RED wire off of the terminal on the thermostat. Leave the rest in place. Then at the boiler turn it back on again.
If the zone valve opens again it is a short and the wiring needs to be looked at. If that is the case I can email you a diagram on how it should be wired.
If the zone does not open with that wire off, then the fault is at the thermostat so replace it.
Let me know how you make out.
Quick question. This boiler has a manual pilot. Will I have to relight it?
Dunno if this makes your analysis any easier but all zone valves work the same way even the questioned one. The two photos are of the questioned valve. the spring tightens or releases depending on whether I turn the heat on or off, which is the same for all. the valves are in the auto position, and stay there. Wasn't quite sure about moving the lever over from the auto position, but they all worked and felt pretty much the same Once mover over---not all the way to manual, the leers did not move when i turned the heat on or off on any.
Sorry one more thing. I checked internally and contact was made and the gears turned.
OK I have followed your instructions. There was no movement of spring loaded gears (stayed closed I assume that is when the spring is not expanded?) in any formula that I conducted with thermostat, boiler switch etc. So i have installed a new t stadt and have my fingers crossed.
heat still flowing Brand new tstadt is set to off.
if the wires are off the t stat does the boiler still run?
Follow me on HT so I can send you my cell number so we can talk. it is simple to figure out, but hard to describe by posting.
If the spring is holding the zone valves closed and you still have heat. the valve may be faulty.
I am following you and I sent you my cell number as well. I guess I would have to disconnect or turn all tstats?
just posted a video of my furnace set up on my youtube channel defendall or firstname.lastname@example.org