Warm radiators in the summer

[RichardRichard]

With the central heating off, but the hot water on, some radiators get warm. The Honeywell zone valve that controls the radiator circuit does appear to switch off the radiator water.

 

[seco services]

Poss the valve is passing ie crud blocking the port or the ball inside is faulty.
Hold the pipes either side of the valve when the hw only has been on are they hot ?

Is it a new problem or always done it ?

 

[RichardRichard]

The pipe on the output side of the zone valve does get hot, but only for a few inche. It has always done this. The return pipe from the upstairs radiators is hot all the way up to the ceiling with the CH OFF.

 

[seco services]

Sounds more like reverse circulation then.

 

[CBF]

as ss said it sounds like the pipework has been installed incorrectly, cylinder ret should always be the last connection before the boiler