Problem with 2 port valve on hot water.

[MGK]

I have a problem with the 2 port valve on my HW system.

The HW stopped working so I moved the valve to manual and it was working. After a while the hw was on continuously even if the programmer was turned off.

I assumed the valve was faulty so replaced the head with a new one today.

All was fine.. HW came on when programmer asked and boiler went off when programmer was turned off. BUT then a couple of hours later when I boosted the water nothing again!

Move the valve to manual fine.

Cant make this out. Seems to me the valve is fine (turns fine with the head off) so the syncron motor must be faulty. But It was brand new this morning.

System has been fine for 18 months since installation so assume it can't be a wiring fault.

Any suggestions?

Cheers

 

[nogoodatfaultfinding]

Cylinder Stat maybe gone.

By opening the valve manually you are overiding everything including the stat which would normally kick in with your timer.

 

[MGK]

I did check the cylinder stat was working. Voltage was passing through when calling for heat and when up to temp was swiching off.

So think cylinder stat is ok.
Thanks for the suggestion though.

 

[nogoodatfaultfinding]

Did you replace the full valve or just the head?

Although 90% of the time changing the head will solve the problem there is the 10% where the full valve needs to be changed as the open close pin which will move if forced by hand will not move under the limited force of a call for heat if you get what i mean!

Try some WD40 on the pin and rotate with some grips.

 

[MGK]

Thanks for the tip, but the pin rotates freely

I can turn it with my fingers. The confusion is that by replacing the head everything was fine, but only for 4 hours or so.

Seem unlikely that a new replacement would develop a fault in this timescale... although anything is possible I suppose!

 

[nogoodatfaultfinding]

Turning as freely as that could well mean that the actual valve is knackered.
The problem with this is that if you have fitted the head whilst the pin was in the manual position then when its reached temp it still will move back to the closed position and when you have tried to boost it it still wont go back to open.

 

[MGK]

Don't think this is the problem because if you move the valve to manual the water heats up fine indicating the valve must be open.

I think I have been unfortunate enough to get another fault on the head and will have to replace it again..but I could be wrong.

 

[ChrisR]

WHat make is the valve?
Did you get an identical head?

You said

The HW stopped working so I moved the valve to manual and it was working. After a while the hw was on continuously even if the programmer was turned off

.

MOving the valve manually rarely puts the boiler on (depends on make/model). The boiler is turned on by a switch inside the valve, when the valve has fully opened.

As you heating is (probably) NOT on at the moment, you wouldn't noitice the HW "Still on".
SO it sounds to me like your programmer is turning it on when it shouldn't, and not, when it should.
There's no valve fault I can think of which would bring the HW randomly on AND off.
Assuming the CH is bahaving itself, you could try swapping the CH and HW wires in the porgrammer to see if things change.

 

[MGK]

The valve was bundled with the unvented cylinder and was an orkli

I replaced the head with a siemens czv2 which was identical and was listed as a suitable replacement

As i mentioned before it was working perfectly for a short while... this is what is so frustrating.