Radiators Coming On With Hot Water - which valve is likely the issue?

[Anon]

Our radiators have started heating up when just the hot water is switched on (not the heating). I understand this is likely due to a faulty diverter valve, but which is it please?

On our system next to the hot water tank we have a Myson MPE222 at the bottom (which the light goes on when the central heating is switched on) and a Danfoss HPA2 (replaced a Sunvic SZ2301) at the top. Both units have been replaced a few years ago, but I understand it is possible they have broken again.

Or could it be the valve itself bottom one replaced two years ago)? Both turn freely with the unit off.

Thank you

 

[Exedon]

Heating valve must be open for that to happen try moving the manual lever to check it's not stuck and spring returns.

 

[Anon]

The bottom Myson 222 can be pushed to manual when the heating is switched off, it doesn't then spring back to Auto if you try switching it back as it is just loose. It returns to Auto when heating switched on/ then off and I can hear it running, it then has resistance again if pushing it to Manual.

 

[terryplumb]

Replace the complete valve,body and actuator.