cental heating problem?

[Tony22]

Hi,

I have a fairly modern central heating system (less than 6 year old) using a Potterton Suprima 40 boiler and Potterton EP2002 controller that has worked fine until the other day. Now the boiler appears to be on constantly 24h a day even when the controller is showing off! The central heating also appears to over rule the room thermostat (radiators still hot even when the room is over temperature). The only way I can stop the central heating is to manually switch the boiler off when it is hot and back on again when it is cold – although, I can control the water temperature in the radiators to a certain degree using the boiler stat. Does anyone have any ideas what the problem is? – Could it be the controller? (Where does the boiler get the signal from if the controller is off and why does it over rule the room stat?), or the motorised valve or even the boiler itself? Any thoughts?

 

[Agile]

Either the motor valve ( or its switch ) is jammed on or the controller is faulty.

It may be difficult for you to decide which.

Tony

 

[Tony22]

I have checked the system and have concluded that the motorised valve is at fault ( I assume if the controller was faulty then the signal to the boiler would still be controlled via the room stat or hot water tank stat). When the central heating controller is off then the orange switch wire on the motorised valve is live sending a signal to the pump and boiler. If I disconnect the orange wire (central heating zone) then the boiler works ok with the hot water circuit. I presume that the valve has stuck in the open position since hot water is flowing through the radiators. Also I have noted that the manual/auto lever appears to do nothing - it moves freely with no resistance. Would this be normal if the valve was stuck open? Anyone know if I can get away with just changing the motor or the whole powerhead or do I need to replace the entire valve which is difficult to do due to it's location. If posible I would like to repair the valve without having to drain the system down. Any thoughts?

 

[Agile]

It sounds as if the valve is jammed open. this may be because of a faulty controller output, a stuck motor or a stuck valve.

Tony

 

[Mikeyboy]

Renew the synchron motor within the valve ,should cure your problem .

 

[Tony22]

Have replaced the synchron motor as suggested - a quick 15 min job (£10). When I removed the faulty motor the valve returned to the normal closed position and the manual/auto lever could be used to open the valve. With the new motor in place the system is now back up and running as expected.
Thanks for all your help

Tony