Heating Bangs Once Loadly when Switching Off

[cucumber99]

Please help. We have a systemn that is about 18 years old, open vented, ideal elan 2.

Everything works fine except when the unit reaches temperature and switches off, as it switches off there is a very large bang that can be heard throughout the house.

Can anyone please advise what the issue maybe?

Other entries on this forum talk of air or scaling but since this only occurs when the unit switches off I am not sure.

Thanks

 

[sambotc]

could possibly be that your thermostat is knackered so the high limit stat is whats telling the boiler to switch off when it hits 95 degrees. Without seeing it it's hard to tell.

Sam

 

[bab]

high limit stat would take out the pilot wouldnt it ? does the pump stay running. some thing must of changed if its just started after 18yrs.is it every time the boiler reaches temp or when the system is switched off by the programmer.

 

[sambotc]

possibly may do yes. To be honest i can't remember what an elan is designed like o the top of my head, is it an interuptor type HLS?

Failing that maybe the start of a failing pump or scale build up.

 

[namsag]

Some elans where auto ignition so it would not knock out pilot.. Low water content boiler possible pump over run fault after demand. Pump should stay on for about ten minutes after demand for heat/hw has stopped