Noisy boiler

[Andagain1001]

Hi
I have an Ideal Classic Condensing boiler (HE12), which is making banging/popping sounds when it is firing.

When it happens it makes the noise every 5-10 seconds, sometimes more loudly than at other times, although sometimes there are no noises at all when it is firing.

The water has only been in the system for about a year and inhibitor was added when it was installed.

Any ideas much appreciated?
Thanks

 

[kevplumb]

has it been serviced

 

[Andagain1001]

Not serviced since installation, about a year ago.
Thanks

 

[greemyamochop]

whats the pressure gauge say?

 

[Andagain1001]

Hi
The system is open vented so no pressure gauge, unless there is one that I don't know about?
Thanks