I have a baxi bahama, approx. 5yrs old, in the last couple of months it has started to make a whistling noise, with HW and CH. It has been serviced, the noise only comes on when CH is cold, some times while running a bath, if you turn down temprature of either noise dissappears. I have checked gas pressure thinking it could be to high, ok. Noise starts when water in boiler gets hot and starts to modulate gas pressure, when water in boiler is hot and gas pressure fairly low noise never there and while running flat out and water in boiler fairly cold noise never there.
