Motorised Valve Siemens ZA-V222C Bangs/Clicks

[ricsmith]

Central heating has been 'stuck on' for 2 days even though the thermostat was set to MIN, and CH and HW were OFF at the control unit. Boiler control dial was set to maximum.
Checking the system, there was NO pressure in the system.
I increased pressure to 1.5 bar, and bled the system since a lot of air in it. I then reduced the boiler control dial to half way (12 o'clock position).
Now the CH no longer stays on when thermostat is low, and comes on correctly when turned up.

HOWEVER .... With CH set ON, & thermostat turned up, the motorised valve (SiemensZA-V222C 2 port zone valve 022) 'bangs'/'clicks'.

Turning down the thermostat stops the banging.
I reached for what looks like a little switch underneath the valve, and it appeared stuck. I gave it not such a strong tug, and the plastic arm came away in my hand.

Any idea how to resolve the banging/clicking of control valve when thermostat turned up ? Does the valve need replacing, or is their potentially a greater issue which has caused a problem with the valve ?

Much obliged for any advice.
R

 

[twgas]

I would suspect the CH valve is stuck and needs replacing, do the rads still get hot when only the HW is on? the clicking and banging is probably the motor turning - cogs broken so it gets so far then springs back.

 

[ricsmith]

Yes That's right - the radiators were still heating up even when CH and HW were off, but as i say, that seems to be no longer a problem following repressurising the system, bleeding radiators, & turning boiler knob down to half. However the control valve still starts banging again when turn thermostat up. I agree it sounds mechanical and I was wondering if I can just replace the motor without needing to disconnect or cut pipes to replace entire valve ? Also wondering if symptoms could in anyway have been caused by lack of pressure, air in system - could this lead to overheating and cause damage to valve ??

 

[twgas]

What I actually asked was "do the rads still get hot when only the HW is on?" (not when both are turned off)

 

[mickyg]

get rid of that valve regardless. Those siemens valves are shockingly poor. Had to remove every one I've seen in the last 2 years. They also fail intermittently which is very unusual for MVs.

 

[ricsmith]

What I actually asked was "do the rads still get hot when only the HW is on?" (not when both are turned off)

Sorry Mick - I can confirm that the rads stay HOT (still get HOT) when ONLY the HW is on, also.

 

[ricsmith]

get rid of that valve regardless. Those siemens valves are shockingly poor. Had to remove every one I've seen in the last 2 years. They also fail intermittently which is very unusual for MVs.

Given the symptoms do you think I can just get away with replacing the motor, without any need to cut pipes ? If so, will any 2 port motorised control valve motor do the job ? My local supplier doesn't stock Siemens anyway.

Not being a plumber, just looking for a little guidance on what's best - order online replacement siemens motor, or replace entire valve including the brass ?

Thanks again for any advice.

 

[twgas]

change the whole valve, honeywell are the prefered choice for most installers

 

[mickyg]

do not get another siemens actuator, you will have to replace it again next year. get a honeywell, danfoss or acl/drayton and it will last a sensible amount of time.

 

[ricsmith]

change the whole valve, honeywell are the prefered choice for most installers

OK, thanks Mick. Was hoping I could get away with just changing the Siemens motor for another one, but if change whole valve I guess I need to drain whole system. Any generic advice on draining and refilling system to a novice such as myself ?

R

 

[twgas]

have old towels/rags etc ready, just in case. also a jubilee clip or cable tie hose on to drain cock. have everything ready and in reach to make sure there are no disasters.
Make a note of wiring connections before removing.
Good luck.

 

[ricsmith]

OK, thanks for the top tips.

So I have a sealed system, with cylinder in cupboard upstairs with a expansion vessel next to it. Also next to it is some kind of filler tap, next to a pressure gauge.

Downstairs is the boiler.

This is what I think I need to do, and I would be grateful if you could spot any mistakes or give any pointers :-

1. Turn off boiler, and leave pump running to assist cooling of rads (how do I leave pump on - is there a switch on it to keep it on ?).
2. Turn off mains supply. Not sure if this is to be found near the boiler downstairs or next to the cylinder. Any pointers which ?
3. Open draincock - I expect this to be downstairs on an external wall.
4. Starting at top of house, open rad bleed valves.
5. Open any draincocks on any inverted pipe loops
6. Remove the fuse from the consumer unit supplying the control valve.
7. Locate the junction box that flex from the valve goes into. Remove the cover of the box and taking note of wiring position, disconnect the wiring.
8. Cut through copper pipe each side of the control valve. Remove valve with attached piping.
9. Take valve to plumbing supplies store and get replacement (not a Siemens !)
10. Fit short lengths of pipe into either side of the valve, to bridge the gap I have left, spring the unit into place, and solder joints.
11. Connect valves flex to the junction box.
12. Insert fuse back at consumer board.
13. Check have closed all draincocks and rad bleed valves
14. Turn mains back on.
15. When hear water flow stop, starting at bottom of house, bleed all rads.
16. Bleed circulating pump by loosening screw in middle of pump.
17. Test boiler and valve by turning on system.

Did I miss anything ?
Thanks again. Keen to not make a mess of this.

How much do you reckon a plumber would charge to do this complete job including the replacement valve, or excluding valve if I buy it ?

R