Heating will switch on but not switch off (Grundfos pump, Danfoss HPA2 Actuator)

13 Dec 2015
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United Kingdom
Hi all,

First time poster here, so sorry for any silly questions! Have a similar issue to the thread below:


However, I changed both of my actuators but here it seems I still see the problem, I had slack levers even when off, but stupidly now I realise it must have been the valve being tight although it's pristine with no limescale so who knew (so the replacement was probably a waste of money as they don't seem to be broken :unsure: ).

I'm stuck as to what to do next, the HPV22 valve for the heating was tight but I loosened it, the hot water one is movable with fingers although now still slightly tighter than CH although the how water one does work.

When I switch the power off and switch it back on, the pump stays off. However, when I turn the actuator to manual it switches on, and when I let the lever go back to auto it doesn't turn off again (even though the programmer is set to off - I have a NEST so switching it on on demand not quite so straight forward, but once it does kick in, then it doesn't go back off again).

What can I do next to figure out where the issue is?
Any ideas greatly appreciated!

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I don't know because I have not been there and seen what you have.

I think that it shows that a DIYer can spend a lot of money replacing parts without actually solving the problem whereas calling a professional to diagnose the problem might well work out cheaper.

To get heating on with my Nest, I just rotate the dial. Or press the button on the Heatlink to over ride it.

Is it just one of the actuators that, when resturned to the closed position, leaves the pump running permanently or do they both do the same?
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Looks like clearing out HPV22 valve by rotating it a bunch of times seems to have done the trick! Wish I had tried this before the buying new actuators, but I will keep the old ones as spares, never know when they may come in handy, reading on the forums they are prone to go.

Thanks for the responses.

BTW on the Nest, you can press the button on the unit attached to the programmer and it will override to switch on (light goes yellow from Green) to turn on / auto mode. Also to pair your base unit with nest controller hold down button for 20s and then let go it will be flashing, you can then go to re-pair on the main nest controller and you will need to enter to code by taking off lid off the base unit and checking code at top which you will need to input.

May help someone in future, as I had to search for it!

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