Zone valve fault - radiators come on with HW

[Andydevon]

Can the more knowledgeable please confirm my system view please?

Y pan converted to S plan with unvented cylinder and sealed heating. Best money spent on the house. I now have an issue that when the HW is on the radiators heat up. I suspect the zone value is faulty. Both valves work when level pushed to the right, trigger pump and the motor winds then back into auto. However the Honeywell one at the top goes back further than the Boss Therm lower one. Suspect it this one that is passing.

Firstly can you confirm that its the Boss Therm lower valve that would be not closing properly?

Secondly can the vale head be removed to manually operate the vale to see if stuck (think I can) With power and motor movement I can exclude power issues as I really don't want to delve into the 'wiring centre' unless I need to replace the unit.

If its the valve I can replace , if its the motor I believe a siemens head unit can be fitted.

Grateful for any advice.

 

[terryplumb]

Does the rad in your pic heat up when domestic hot water only is selected as well as when central heating is selected ?
Follow the pipe from the Honeywell valve ,does it go to the cylinder ?

 

[oldbutnotdead]

Usually the manual lever doesn't open the valve far enough to trigger the microswitch (on the Honeywell anyway).
There's a few things you can check first before you start swapping heads etc out- it wouldn't be a surprise if the installer has fallen into a wiring trap causing your problem.

First job (with cylinder and rads cool) check the manual levers- make sure they are moving the valve (should take a bit of force to move the lever).

Second- set controller to HW ONLY. See which valve has opened (the manual lever on the open one will need very little effort to move it), see which pipes get warm. If nothing happens, adjust cylinder stat to stimulate demand (note where it is first)

Next, set controller to CH ONLY. Repeat valve and pipe checks (again adjust room stat to stimulate demand if needed). In both cases check pipes far away (couple of metres) from the pump and valves

In your pic the rad to the right appears to be set up so it's on whenever boiler is running so don't be fooled by that one.

 

[Andydevon]

Terryplumb - Radiator heats with either HW or heating - designed to create an airing cupboard as this was where the hot water tank lived. Guess who wanted to keep the airing cupboard?

Pipe form Honeywell goes to cylinder.

oldbutnotdead - first job done both move. Second job will do.

 

[terryplumb]

I assume the system has previously worked as it should ,and your issue has just arisen .
If so ,the lower valve is either stuck open or it's being energised when it shouldn't be. Not familiar with that make but I think the actuator can be released from the body.

 

[oldbutnotdead]

@terryplumb I'm wondering whether the installer has used switched live from the controller on the microswitches as well as motors so latching both circuits- just waiting to see whether valves operate individually first.

 

[terryplumb]

I asked if the system previously worked ok , if it did that rules out a wiring issue. We await the OP's response.

 

[Andydevon]

Yes system worked perfectly for years.