C+M boiler - no pressure

[jimmy6flats]

Hi

I have a Chaffoteaux and Maury Britony Combi 80 that came with the house I've just bought. Everything seems to be working well with both the DHW and CH, but the boiler makes a dreadful groaning noise when I turn on a hot tap.
On closer inspection the pressure gauge is down at 0 at all times, until I turn the hot tap on when it spikes to 1 and stabilises at around 0.5. This is when the groaning noises begin, and on shutting off the tap the boiler shakes and the pressure drops to 0.

I have looked on the net for the manual, but have found nothing that tells me how to adjust the pressure. Is there an easy way to fix this, or do I have to get a pro to look at it?

Thanks,

Jamie

 

[Rob]

see the FAQs

 

[jimmy6flats]

I have checked the FAQs, and understand that I have to top up the pressure in the expansion vessel, but am having trouble locating it. Is there anyone out there with experience of this particular boiler type that can help?