Pump not shutting down

[josh 10]

Hi.
I have a strange problem. I cannot stop the circulating pump from running on my heating and hot water system.
I have had problems in the past with a Danfoss motorised valve not shutting completely on the hot water side and causing a continuous running of the system. Removing the motor and freeing off the valve, so it would completely close has cured the problem. This time I have checked both valves, hot water and heating, the heating valve was not completely closing. I have freed off both valves to make sure they operate freely and close but the pump still runs. If I take the motor off now the valve looks to be completely closed when either stat is not calling. The room stat is set to the lowest setting, in fact I can hear it clicking so believe it is not calling for heat and the tank stat is in the same position. I can also hear this clicking so assume it is closed. The boiler is set to the lowest position as well, so it is not coming in. I can also hear the boiler stat clicking in and out. The pump continues to run.
Unfortunately I did not have a multimeter with me at the time so have not yet checked if there is any call from either valve when they are closed. I believe the stats are working because I can see the motor opening and closing when the stats click in and out.
I am assuming there is a micro switch in the motor that shuts off the signal when in the closed position. Could it be that the inside of the motor is gummed up and the microswitch is not shutting off the call to the pump.
Sorry to ask the question before checking electrically but this is a holiday home and it will be a few days before we can get back with a meter, so I thought I would post now to try and see if people can help with other suggestions. I have in the meantime shut everything down. Not cold enough here to worry about freezing.
I am an engineer but not in heating so I hope I have explained the problem clearly.
Any ideas would be appreciated.
Thanks in advance.
josh.

 

[jtsplumbing]

If the valves keep sticking I would advise that the system is cleaned then new replacement valves be fitted take it the pump stops when system is not calling for heat ie off at timer.

 

[josh 10]

If the valves keep sticking I would advise that the system is cleaned then new replacement valves be fitted take it the pump stops when system is not calling for heat ie off at timer.

Hi Thanks for posting.
The pump does not stop when when timer set to off on both HW and CH. Pump only stops when I switch off at the wall switch for the system.
josh.

 

[jtsplumbing]

Pos that you have a faulty controller sending out power

 

[Last Plumber]

Where is the pump wired from?

If it is wired from the MV's (motorised valves) it could be that the micro switch inside one of them is stuck in the closed position.
There is a permanent live to the micro switch, so the programmer being off will make no difference. That only puts live through the relevant stat and onto the motor in the valve.

 

[Best]

Almost certain to be the Danfoss motorised valve head faulty. Micro switch, as above post.
Visually, you won't notice anything wrong.
Personally I would replace all Danfoss motorised valves (complete body and head) with another brand, as I find them unreliable.