[Tom Vaught]

I have a 4 zone hot water system, over the years I have had all 4 of the same water controllers replaced. There Are more modern (newer) designs but the old ones ARE built like a tank. Typically they drain the water and cut out the old unit and install the pipe and new unit in the system. Mine developed water leaks after 40 years.

In your case the control circuit for the device apparently failed.

The other thing is do you have all of the air out of the system?
Many times when the control fails over time the valve lets air into the system and less water and more air makes the water temp thru the system much hotter.

Tom V.

[Half-Inch Stud]

Originally Posted by Tom Vaught

I have a 4 zone hot water system, over the years I have had all 4 of the same water controllers replaced. There Are more modern (newer) designs but the old ones ARE built like a tank. Typically they drain the water and cut out the old unit and install the pipe and new unit in the system. Mine developed water leaks after 40 years.

In your case the control circuit for the device apparently failed.

The other thing is do you have all of the air out of the system?
Many times when the control fails over time the valve lets air into the system and less water and more air makes the water temp thru the system much hotter. Tom V.

Air is probably mostly out.
Temp control circuit locking Thumbscrew lost torque, so it sprung up in temp and couldn't press cluck switch.

Thank God there are no Zone Valves: grew up with those, and the 1st 2 home i bought had them: designed to fail in the electric coil. Then later the inlinw water switch button corrodes out.

The Cast Iron Radiator system has a Cast Tee for each radiator pipe ( in and out). a pair od Tees can be 3' apart on the 2.5" Main flow, and flow still occurs to the Radiator. no moving parts so flow must be encouraged by an internal flow divider huh.