Whistling/hissing boiler

[rugbyref]

I have a 7/8 year old Alpha CB24 combi boiler serving a self contained office attached to the house.

Last night the boiler started whistling. It is still doing so. The CH is switched off. Drawing HW does not change the noise which sounds like pressurised air escaping.

The pressure in the system was just within the green area of the dial at 0.75 and I have increased the pressure to just over 1.0 - no change to the noise. I switched off all power to the system as well but the noise continues, so it isn't a pump or fan. Overnight the noise seems to have changed from a whistle to a hiss. I can't really believe there is any pressure left to escape. The CH is still switched off.

I am loathe to call out an RGI engineer before having some handle on what the problem is. All other posts refer to whistling noises when the boiler is working.

Any thoughts gratefully received.

 

[Boilerman2]

Turn off the cold water inlet valve and see if that changes anything it sounds like a water leak TBH possibly in the domestic water cct (could be under a floor somewhere possibly which is why you can't see it!

 

[rugbyref]

Turn off the cold water inlet valve and see if that changes anything it sounds like a water leak TBH possibly in the domestic water cct (could be under a floor somewhere possibly which is why you can't see it!

Thank you Boilerman2.
Have now tried that but it has not made any difference. It doesn't sound like a water escape if that's what you mean. It still sounds like a leaking seal on a pressure cooker but there isn't a heat source to create the pressure.

 

[twgas]

try turning off the main stop cock.

 

[rugbyref]

I have turned off main stop cock and it has made no difference to the noise.

 

[jackecole]

is the aav cap loosened?

or is there a filter/cartridge on the inlet a bit clogged/split etc?

where does it sound like it's coming from - what area of the boiler/system?

 

[rugbyref]

After all that it was nothing to do with the boiler!!! It was a thermos flask sat on the worktop below. As soon as I picked it up to move it to allow access to the heating flow and return pipes, the noise stopped. I haven't worked out how it was making a noise, but it has now gone. So, happy days!!