Actuator Problem?

[TomP]

Occasionally (once every couple of weeks) my central heating system does not fire up. It has only started doing this in the last few months Thanks to DIYnot I tracked it to the Motorsied Valve (Danfoss HSV3B28). If I slide the arm on the top of the valve to manual, everything starts working ok.
When the arm gets to half way across there is a fair bit of resistance and I have to push quite hard to get it over....is that normal?

It looks like I can buy just the top part of the MV (the actuator?) and it looks fairly easy to replace...is it likley this is the problem or should I get a heating engineer to change the complete MV?

Thanks for all help.

 

[Boilerman2]

Remove the actuator head, (2 silver screws) make sure the spindle on the valve is free to rotate, you will need a pair of pliers to grip the spindle, if it is tight, or there is signs of leakage from the spindle the whole valve should be replaced, if valve is OK you can fit a new HSA3 head, make sure you isolate the electrical supply to the system, and make sure the wires go back to the correct terminals and all should be well

 

[TomP]

Thanks Bolierman2, I'll try what you said.

What would cause this to stop working intermittently?

Is it right that there should be a fair bit of resistance from the arm when it gets half way across?

 

[Boilerman2]

The reason its playing up is the fact that it's a Danfoss i,m afraid, they don't make the best actuators in the world!

 

[ChrisR]

Is it right that there should be a fair bit of resistance from the arm when it gets half way across?

You'll be certain when you get the head off, the valve spindle should go round smoothly.
"fair bit" is hard to quantify!