Hi all,
since about a month ago our CH combi boiler is humming (or should I say "singing"?) in a very noisy fashion, so that we better not leave it on overnight because it may wake us up. It's not continuous, just every now and then for half an hour at a time. When I open the hot water tap it the sound stops for a few seconds to continue shortly afterwards... The sound is definitely coming from the boiler and not from the pipes as I first thought, and it does not depend if the boiler is firing.
Any idea what that could be? I have a plumber coming in end of this week anyway -- don't want to touch anything with gas inside myself -- but before he wants to sell me a new boiler as a fix ;-) I wanted to ask for some opinions here.
Additionally: is it normal that if the boiler was switched off for a few hours (overnight) that a lot of air has collected somewhere inside? Every time I switch it on, I hear some ugly stuttering or flushing sound while the air is removed. We already had the expansion vessel and the pressure valve replaced recently, and the system pressure is very stable since.
Thanks in advance for any ideas! Peter.