Can boilers cause a whacking sound?

[George]

ie a loud crack noise.

I'm getting woken up at random times of the early hours of the morning by a loud crack type of noise,my neighbours away and now I have had time to think, this occurs every time she's away ie the boiler not getting used for anything upto a week or two?

Tis bloody annoying and I'm trying to fathom out whats doing it? short of staying up for a couple of nights as its random I don't think I can pinpoint it hence me asking whether boilers creat a loud bang or noise when not in use or are just plain too old and need replacing.

TIA

[TheScullster]

"George" wrote

We had a boiler that used to ignite explosively, which may have sounded like a crack from the outside. This was intermittent and no doubt due to the position/size of the pilot relative to the burner. No reason why this should be happening only while your neighbour is away though!

Phil

[meow2222]

If the pump doesnt overrun, water is liable to boil in the heat exchanger when the boiler stops. In a restricted space like this it sounds like banging. Suspect the pump overrun circuitry - if there is any. If not, turning the circulation temp down reduces the odds of it happening.

NT