Vaillant Thermocompact VU 182/1E CH sticking on

[Andy_CC]

Our old Thermocompact VU 182/1E has performed faultlessly for years but recently there's been an intermittent problem with it not shutting down when the room thermostat cut-off temperature is reached. The room stat appears to be working ok, it's wireless and clicks off when the set room temp is reached but on occasion the boiler continues running.
My thoughts are that it's possibly a control board issue - sticky relay?

Advice appreciated.

 

[Gasguru]

More likely a motorised valve sticking on...

 

[Andy_CC]

More likely a motorised valve sticking on...

Thanks - that would cause the boiler to stay on?

 

[Gasguru]

The room stat just tells the motorised valve to open on a heat demand. Once the valve opens it operates a switch inside to command the boiler to fire up. A valve stuck open will keep the boiler on regardless of the thermostat setting.

 

[Andy_CC]

The room stat just tells the motorised valve to open on a heat demand. Once the valve opens it operates a switch inside to command the boiler to fire up. A valve stuck open will keep the boiler on regardless of the thermostat setting.

Thanks, I'll investigate the motorised valve next time the heating sticks on. Appreciate your help!

 

[Andy_CC]

I've investigated the CH motorised valve (Honeywell 272848).
With the motorised head off I can turn the valve spindle quite easily by hand. So this would indicate the head being intermittently faulty?

 

[ianmcd]

The motorised valve actuator (head as you call it) contains a small micro switch, if the radiators are getting warm when switched off then the synchron motor is seizing, if they arent but the boiler keeps firing the micro switch is sticking, replacing the actuator will sort both

 

[Andy_CC]

The motorised valve actuator (head as you call it) contains a small micro switch, if the radiators are getting warm when switched off then the synchron motor is seizing, if they arent but the boiler keeps firing the micro switch is sticking, replacing the actuator will sort both

It's an intermittent problem, everything can be fine for days, then we get the continuous running problem. The radiators definitely get hot.

 

[ianmcd]

then the synchron motor is on its way out it will jam up soon you can just replace the motor but can be fiddly on some makes if replacing the actuator buy one of these makes the job a lot easier, but as your stat is wireless when the heating is on whn not meant to be check that the receiver is not still calling for heat

REGE105 REGIN 5 WAY PLUG / SOCKET WITH STRAIN RELIEF 5060026573891 | eBay

With strain relief. Complete with locking latch for added security.

www.ebay.co.uk

 

[Andy_CC]

then the synchron motor is on its way out it will jam up soon you can just replace the motor but can be fiddly on some makes if replacing the actuator buy one of these makes the job a lot easier, but as your stat is wireless when the heating is on whn not meant to be check that the receiver is not still calling for heat

Yes I did check that already.