How can I fix a banging noise in CH system- 14 years new drayton and sunvic valves -sealed system?

[bomitie]

This started last night at 11.25 and has me completely flummoxed. A banging noise that is hard to track down. When I'm in Bathrooom that has airing cupboard it seems to come from hallway when in hallway it seems for come from cupboard. The system is a grant boiler in an outside house, purpose built, it is an unvented condensing system with a red expansion tank in boiler house and a pressure clock that has a red hand stationary at 20 and a black hand that moves but never seems to go beyond the red. Drayton motorised valve in BH and a SUNVIC in the airing cupboard that controls HW. The tank in airing cupboard is huge and is a Santon Premier Plus that also has an expansion tank. It also has a HW thermostat on pipe at top of tank. The pump is a TERRIER . The system still works but today it seemed to me that the rads got exceptionally hot but its 5 outside. In fact if they get that hot all the time I would be pleased. I have replaced the drayton myself about 12 months ago, SPRING WENT. the sunvic always gave bother but I replaced the actuator bit Feb 2018.

System is 14 years old, could be a bit more, never drained, has that clever rust inhibitor installed at my insistence.

I have turned Boiler thermostat to min and turned off the one on HW tank.

Help!! and is it dangerous.

 

[Knappers]

Sorry, there's so many things it could be.
Possibly overheating which can cause damage to components.
Best to get it looked at but if thats what it is I'd perhaps start with the pump?

 

[bomitie]

Sorry, there's so many things it could be.
Possibly overheating which can cause damage to components.
Best to get it looked at but if thats what it is I'd perhaps start with the pump?

Thanks for reply. I turned the thermostat down on the boiler and let everything cool off turned heating back on and so far no banging. Will try HW tommorrow.

The starnge thing is the pump is so silent and quiet I cant even tell if it is circulating!!

 

[bomitie]

Just an update I have turned the boiler theromostat to min and noise gone. Spoke with an electrician who siad that was an indicator that the thermostat was on the way out but if I keep boiler at min it should be ok for a good while. I had it at max as I wanted top heat and thought that was correct for a condensing boiler. Is it easy to fit the thermostat?