Weil McLain 1107-1 baseboard hot water wont shut off

Multiman

Integrated domestic hot water and baseboard hot water. Stopped responding to thermostat. Will only do constant full on baseboard hot water heat, will not cycle off. Replaced thermostat. Checked thermostat connection to furnace. Is next step replacing control board?

109A_5

Were both the domestic hot water and the baseboard thermostat / aquastat wires disconnected at the boiler ? Does the control board seem like it is actually receiving a call for heat ? What is the actual boiler model ?

mattmia2

could be a stuck end switch or zone valve too if it is using zone valves.

HVACNUT

If you have the CGt, the 3 way valve could be bypassing. What model and Series boiler?

Multiman

It is the Cgt-5pin. Series 2. Looks like it's from 2014.

Multiman

It's only one zone, for one floor, for baseboard hot water, but it also supplies domestic hot water. It is supplying hot water just fine. The problem is that the heat won't turn off in response to the thermostat. It is running heat nonstop.

I read on here someone else with the exact same problem on what sounded like the same unit.

Jamie Hall

Somewhere something is telling that boiler to run. You will need to work through the controls to find what controls what… can't tell without being there or having a pretty complete wiring diagram to work from.

Multiman

So you'd say I have to do that, before jumping to replacing the control board.