Hot water heating when off

[Daveyah]

Hi,

my hot water is heating up when the CH only is switched on. It is a 2 port 2 zone with loft header and HW water tank in the airing cupboard.

The HW zone valve actuator is running ok though a little stiff at the end when it closes. So I removed it and made sure the valve spindle is fully in the closed position. It appears the HW is still heating.

How often do the valve bodies fail and allow hot water to pass, which is what I am suspecting now as the pipe on the other side feeding into the tank is hot.

Thanks

Dave

 

[seco services]

depends on many factors.
how clean system water is
what make the valve is some are better quality than others.

 

[Daveyah]

Thanks.
It's a Drayton ZA5. I have bought a new one to fit this weekend and looking inside the new one I am not surprised it has failed. The guts look pretty cheap to me. A rubber flap held onto the spindle with a bit of bent metal. I bet that is where it has failed. I'll put what I find here for others once it is off.
No expense spared there.

 

[Daveyah]

Valve changed problem fixed.
Old valve looks OK but when I filled the feed end with water and held the valve off hard by hand the water still went through. The new valve passed this test. So the flap must be worn in some way.