Yes, dB is a log scale, so 3dB is equal to doubling the sound intensity. However, apparently a 10dB increase is required for it to be perceived as twice as loud though...
@vulcancontinental, sent you a PM. Thanks!
Thanks, I didn't think to look there! The Intergas HRE 18 SB is rated at 45dB, which is a fair bit lower than the 50dB for the Unica MAX S 20. Not sure how much different it would be in real world conditions though...
Apologies for hijacking Gizmo's thread but I'm in a similar situation and so thought it best to add a reply here rather than create an entirely new thread.
Here's my current system:
Baxi System 100 HE Plus 22kW boiler (just over 17 years old and on its last legs)
Megaflo 170l unvented hot...