Radiators getting hot when heating switched off

[blackbirdxx]

Hi,
I had a system boiler with new rads fitted a year ago in my 3 bed semi. I eventually got the plumber back to check the system as a number of rads are coming on with the central heating switched off and the hot water switched on. Unfortunately the problem is not so evident at the moment as the central heating is on a great deal now the weather is getting colder. Anyway, the plumber checked the valves manually and said everything was working as it should. We left it at that last week but today I switched the heating off totally with the hot water on to see if the problem was still there. Again I confirmed that a number of rads were coming on hot when the heating is switched off.
Any ideas of what I should be asking the plumber to do next? I don't want to waste another visit from him as he's quite difficult to get hold of. The levers on the Honeywells appear to be in the correct positions, could it be something else electrical that is causing the problem such as the time clock??
Any assistance appreciated...

 

[CBW]

Any ideas of what I should be asking the plumber to do next?

You shouldn’t be asking the plumber what to do next.

I don't want to waste another visit from him as he's quite difficult to get hold of.

Don’t waste your time. I’d be getting another plumber/heating engineer in. I’d say it’s going to be a piping arrangement or a failed 3 port (if that’s what system you have). Do you know if you have a y-plan system?

 

[blackbirdxx]

Its an 'S ' plan system with 2 Honeywells.

 

[ianmcd]

Most likely that the return connection from the HW cyl is not the last connection in your system, what you are experiencing is called reverse circulation

 

[oldbutnotdead]

As @ianmcd , likely a design fail if the valve(s) are working properly. Pics/scruffy sketch of pipe layout? (Favourite fail is when retubing an old gravity hot water system)

 

[blackbirdxx]

Hi,
Switched the heating on and the water

with the wall thermostat set to as low as poss and certain rads are getting hot. Ambient temp at the moment is about 16deg C. I attach pics of the system which may help....