Yes, another Motorised Valve issue - advice needed

[acideraser]

This forum helped me a lot many times in the past and hopefully will help again.
I did search and despite there are many posts related to the valve issue, I could not find one similar to mine.

Motorised valve on CH zone 1 circuit does not seem to work correctly and doe snot open fully when it is supposed to open.
Initially I can open it manually by pushing lever up and if left open, heating works fine.
After sometime, it closes and is not able to open again fully and the manual lever stops just above the middle point and no table to go further.
I discovered that if I switch off the power, it starts working again (can feel resistance of the motor as usual and it returns back normally). When it is locked in open position manually, heating works as expected.
When I open the cover, the valve head is very hot to touch but this is probably because of hot water in the pipe?
I also removed head and valve seem to move freely. System is about 9-10 years old.

I've got a replacement valve but I am not sure if I need to replace the the whole valve assembly, the motor or the ball inside the pipe?

Is it possible to confirm this is the valve and not something else?

System configuration:
System config:
It is a new system installed by in the extension which consists of:
- Vaillant ecotech 624 system boiler v.6.08
- Unistor cylinder
- VR 61/4 Control centre v.4.18
- VRC 470 weather compensator (and thermostat used for UFH zone downstairs) v.4.20
- VR 81/2 thermostat for CH upstairs v.2.02
- DHW circulation pump

CH is zone 1, controlled by VR 81/2 upstairs, Honeywell V4043H1056 motorised valve
UFH is zone 2, controlled by VRC 470 in downstairs, Honeywell V4043H1056 motorised valve

Thanks!

 

[CBW]

Remove the head, if the spindle can be moved easily by hand then just the head or motor. If the spindle is stiff then the whole lot.

 

[acideraser]

Thanks, if I need to replace the whole lot, do I need to
If I need to replace the whole lot, can I do it with water in the system ?
I think I can isolate it from the boiler side, but there is nothing on the other side going to the radiators.

 

[CBW]

Thanks, if I need to replace the whole lot, do I need to
If I need to replace the whole lot, can I do it with water in the system ?
I think I can isolate it from the boiler side, but there is nothing on the other side going to the radiators.

Tbh, not entirely sure. I don’t work on system boilers, but if they’re anything like combi’s, you can relieve the pressure and that’s it covering any electrical parts to prevent water ingress.

 

[acideraser]

when we replaced radiators I did not have to drain the system - is this what you mean ?

 

[CBW]

when we replaced radiators I did not have to drain the system - is this what you mean ?

It could be, how were your rads fitted if not drained?

 

[acideraser]

It was only one radiator replacement, once disconnected, old radiator was drained but water did not come from the pipes, so no need to drain the whole system.
Then new one was connected and that was it.

 

[CBW]

It was only one radiator replacement, once disconnected, old radiator was drained but water did not come from the pipes, so no need to drain the whole system.
Then new one was connected and that was it.

Should be ok doing the same then

 

[Agile]

One point you need to be aware of is that those motor valves act as a relay and the switch applies power to make the boiler work.

However when manually put in the open position it does not move far enough to operate the switch. That is only done when it is motor driven to the open position.

 

[acideraser]

Thank you sir. I thought that in this system boiler is activated by VR thermostat calling for heat via control centre or is this not the case ?

I am not happy to leave it in manually open position though, and want to replace asap so that all works correctly.

 

[Agile]

The room stat is used to supply the valve motor to open the valve.

So any valve being opened powers the boiler to on by it's relay action.

 

[Mister Banks]

The room stat is used to supply the valve motor to open the valve.

So any valve being opened powers the boiler to on by it's relay action.

Not when using the Vaillant control centre. I don’t think the microswitch is wired to anything. The control centre decides which zone valve to open as required and fires the boiler itself.

 

[acideraser]

Thanks everyone, replaced the valve head and all seem to be working as expected, so far so good