Upstairs rads on all of the time

[Dmac234]

Just been round to my mum and dads and for the last three nights the radiators upstairs have been staying on continuously even with the thermostat turned right down.Downstairs rads are working fine.Not too sure of the finer details of boiler make and the like.It is quite an old system with hot water cylinder etc.
any ideas?

Cheers

 

[JohnD]

it will be either gravity circulation, since it is the upstairs rads that are warm, or possibly a 3-port or other motorised valve that is old and leaking a bit to the heating circuit when it should be on hot water only.

you need to find out what valves and thermostats it has. Post photos if you can.

If it is gravity feed to HW cylinder, and no cylinder stat, the boiler will tend to run even when there is no need for it, which is wasteful.