Actuator Valve Honeywell VC6012 runs non-stop

[BiggDan]

The actuator valve which determines whether the combi boiler is heating for hot water or the central heating system is in constant motion. With the heating system turned off at the boiler and the hot water not demanded the switch still runs. I realized this when it started making noise while switching.

I pulled the electrical connection with the switch in the hot water position and left the heating off with a plan to call the maintenance guy. A friend suggested the system pressure was low so after being off for two days I reconnected it and raised the pressure a bit. It worked at first without changing the pressure but I raised it anyway at the suggestion of my friend. It was OK for two days and now it is back to it's old ways. Any suggestions?

Thanks,
Dan

 

[andytw]

From my somewhat limited experience these things do fail in the manner you describe. The valve part will be OK but it is the actuator that has failed. These can be replaced without anything or anyone getting wet and I would suggest you use the same make of actuator and not a cheaper "equivalent".
They can be repaired but as your fault will either be a microswitch or the synchron motor, if it were me, I would just swap it.

andytw

 

[BiggDan]

I took the actuator apart and burnished the contacts. The mechnisim was a bit rusty, looks like the valve leaks a bit. It has been "working" until today. It is in constant motion again.

"Working" means with the central heating turned off it would cycle through to the central heating position and then back to the hot water position after each time the how water was used. The valve still makes a noise as it cycles.

My question is what signals it to cycle? Here is what the book says:

Depending on the model selected they can be controlled by a low or line voltage SPST or SPDT controller, such as a room thermostat, aquastat or flow switch. Through internal logic the actuator only takes power while driving the valve to the commanded position.

It looks to me like the three wire input is just AC.

Also, when I took the actuator off today it had some water in it. It looks like the valve leaks a bit. Is there any way to fix that without unsoldering the three way valve?

Dan