Fault on Danfoss mid-position valve

[Old_Badger]

I have an interesting fault on my Danfoss mid-position 3 port valve.

If the valve starts unactivated (DHW position) and there's a call for CH only, then it works every time. So the actuator moves through its full extent and both internal switches work faultlessly.

But if the valve starts from its mid-position (DHW and CH both called for) and the call changes to CH only, then sometimes a fault occurs. The actuator doesn't fire up the boiler.

I have tested the electrical output when the fault occurs and the orange wire is not signalling the boiler to come 'on'. So the second internal switch in the actuator cannot be switching properly. I can 'overcome' the fault by tapping the actuator sharply with my finger tips. This must jog the motor and make the second switch work!

Have other people experienced this problem where the mid-position valve fires up the boiler most times when only CH is called for, but not always because the second internal switch doesn't work occasionally?

 

[CBW]

I haven’t worked on many 3 port systems, but I’d say you need a new actuator.

 

[DP]

When both CH and HW are calling and HW is satisfied, no move to continue heating, then You have cylinderstat wiring issue.

calling for heating with HW off, the timer positions the valve to heating position the actuator then makes second switch making orange live

 

[Old_Badger]

When the fault occurs I can overcome it by tapping the actuator sharply with my finger tips. So I don't think the fault is caused by anything outside the valve and actuator.

I think it's a mechanical issue. The valve is more difficult to turn now than when it was new. And I imagine the internal switches could have become stiffer. Does anyone know whether this happens with micro switches?

In any case I know that both switches work when the motor gets a full run-up towards them. And the occasional fault only seems to occur when the actuator is starting from the middle position.

 

[DP]

When the fault occurs I can overcome it by tapping the actuator sharply with my finger tips. So I don't think the fault is caused by anything outside the valve and actuator.

I think it's a mechanical issue. The valve is more difficult to turn now than when it was new. And I imagine the internal switches could have become stiffer. Does anyone know whether this happens with micro switches?

In any case I know that both switches work when the motor gets a full run-up towards them. And the occasional fault only seems to occur when the actuator is starting from the middle position.

Plod on old chap. Reading instruction and following them is not your strong point. I am out of here.

 

[Old_Badger]

I have replaced the actuator as you suggested CBW. And I've replaced the valve itself for good measure.
Both were at least 8 years old, so I suppose they haven't done too badly!

The system now seems to work perfectly. So I don't think there was any kind of cylinder stat wiring issue.

I am indeed an old chap, but I'm not sure what instructions you wanted me to read and follow DP.

 

[ianmcd]

I am indeed an old chap, but I'm not sure what instructions you wanted me to read and follow DP.

@DP is probably an older chap than you