Radiators still on when heating is switched off !!!

[tdevans]

Looking for your thoughts - any would be most appreciated...

Have a central heating system (in a tenanted house) with two actuators (valves)... I have recently had the whole system rewired (as it wasn't working property) with the exception of the wire to the thermostat.

All seemed ok, but the tenants have just been away for a week, and turned the heating off at the control panel while they were away - when they returned, it was still off at the control panel, but the radiators where on !! They have got the roomstat turned down to 10 degrees, but they are not turning off..

It is just two wires to the thermostat - am I wondering if it is worth replacing the wire to the Thermostat - when it was rewired, the heating responded to the Thermostat being turned on and off..

Have no idea if it;s an electrical, or plumbing problem, so any input would be great

kind regards

 

[tdevans]

couple of bits to add, in the hope it might help..

Don't know the name of the boiler - very old hot water tank (long and thin)

Actuactors are Sunivic and were replaced about 6 months ago

Timer - I can't remember the name, have had a good browes and cannot find it - it has a clock face type set up, rather than electronic - again this was new about 6 months ago..

The Pump on the boiler was also replaced about 6 months ago

The tenants have just got a gas bill for over £300, for 2 months gas, which seems very excessive - 3 bed 1930 Semi

Sorry I don't have more info, had hoped I would find the timer details