Help needed - UFH not working. Grundfos UPS2 25-40/60 potential replacement, Valliant system

[Rodders53]

As said earlier, on latch, auxillary switch does not operate. That is the case with all valves. There might be an odd one that rule does not apply to

A temporary solution would be latch open the UF heating valve and let another zone fire the boiler and boiler pump

Don't selectively (mis)quote me, please.

I am suggesting to OP than the manual opening is allowing the valve motor to then operate as designed due to a mechanical (or possibly intermittent electrical) issue. Thus valve microswitch makes it work --- until nest time!!!

 

[DP]

am suggesting to OP than the manual opening is allowing the valve motor to then operate as designed due to a mechanical (or possibly intermittent electrical) issue. Thus valve microswitch makes it work --- until nest time!!!

How does manual opening of valve make the motor operate?

 

[Johntheo5]

If the valve was sticking shut then opening it manually might mean the motor torque is then enough to keep it open but obviously there has to be 240V on the brown wire to the motor.

 

[acideraser]

Thanks to everyone again for your replies.
Unfortunately the trick with manually opening valve doesn't work anymore and pump doesn't come on.
I think if I leave it open long enough the hot water eventually gets into the UFH circuit and heats the room but I am not sure this is good idea as in my understanding this will add more strain on the heating pump inside the boiler?

Below is the system diagram. There is no current on HK2-P terminal in the control unit which is connected to the valve and UFH pump.

Could this be a fault developed in the control unit (been faultless for over 8 years, and no one touched it until now) or something wrong with the settings?
DHW and Other heating circuit are working fine.

 

[acideraser]

This is getting weird now - pump and valve suddenly came on today and right now all is working fine, though not sure for how long...

 

[oldbutnotdead]

There are many possibilities- relay getting a bit lazy, microswitch likewise. Get yourself a multimeter, next time it plays up you need to be checking for voltage (live to earth and neutral to earth )- either start at controller and work forward or start at boiler and work back.

 

[SpecialK]

When its next in fault give those white relays a good thump with the handle of a screwdriver.

 

[dilalio]

Initiate a demand for the UFH and listen for the microswitch to click.
Cancel the demand and listen for the MV to wind back under spring tension.
If there's a click you should then hear/see the pump come on.

You can even take the casing off the MV and manually latch it open and operate the microswitch with an insulated or non conductive tool/probe.

Don't electrocute yourself.