Cylinder always contains (very) hot water

A problem has developed with my central heating system during the past week or so.

It is a gravity fed system (oil powered) and recently we have noticed a couple of the radiators being colder than normal (noticably the bathroom next to the cylinder). In addition, the cylinder seems to permanently stay hot (which is the main concern)even when the hot water is swtiched off at the control pad. Struggling to understand why the boiler may be able to heat up/stay hot when control pad is \\\'off\\\' (could it be running from the room thermostat?)

We operate our central heating by having the control pad permanently \\\'on\\\' continuously but controlled by the room thermostat - could this affect the hot water? (although it hasn\\\'t previously been a problem).

Would be grateful for any ideas.

if it is a gravity system you cant have the heating on without the water whatever the programmer says

try bleeding the cold rads

Thanks for the swift response.

The radiators seem fine (bleed the bathroom one and cold water comes out).

Water has started getting significantly hotter during the past week or so in addition to the radiator going cold. I left the house for c. 4 - 5 days last week and switched both heating and hot water to the off position on the control pad to come back and find the cylinder red hot (with radiators all off as expected).

If I switch the CH and hot water off on the control pad should I expect the cylinder to run cold?

Do you have an immersion? Is it switched on? Maybe the stat has gone?

Thinking about it, it could well be the thermostat - will change it this weekend.

Thanks for the help guys - expect a new issue posted on Monday!

It would be worth connecting a 2 port valve (Honeywell 4043H Or Danfoss HPA2 or similar) in the cylinder pipe, and a tank thermostat to conrrol it. That way you don't have to heat the water when it's hot enough.

ahhh c plan