Boiler / heating problem

[CADmanJP]

We turned our heating off last night and woke this morning to a warm house. I have turned the timer off and on again and even turned the thermostat down to 10 degrees yet it is still running at ~20 degrees.

We did notice a loud banging noise last night, not sure if this is the cause?

Our boiler is a Potterton Prima and the programmer switch is a Honeywell ST6450B.


Does anyone have any tips as to how to find the problem.

 

[corgiman]

whee is the boiler situated?

could be a frost stat kicking in

 

[CADmanJP]

The boiler is on the external kitchen wall.

Update - up until today the heating appeared to be working as if on the 'timed' programme even when it was on the 'off' position. The water still heated up on the 'timed' programme. Tonight the heating went off 2 hours prior to the programmed off time and the red light was still on for the hot water yet the boiler was not igniting.

Also the thermostat does not make a difference, turning it down to 15 degrees does not make the rads cooler.

Is this an electrical problem?

 

[CADmanJP]

The boiler is on the external kitchen wall.

Update - up until today the heating appeared to be working as if on the 'timed' programme even when it was on the 'off' position. The water still heated up on the 'timed' programme. Tonight the heating went off 2 hours prior to the programmed off time and the red light was still on for the hot water yet the boiler was not igniting.

Also the thermostat does not make a difference, turning it down to 15 degrees does not make the rads cooler.

Is this an electrical problem?