Can flue slope cause whining /whislting sounds?

Hi all, sorry, I never got notified of any replies, was surprised to see so many.

To paraphrase a famous someone in Bush's cabinet, "I know what I know, and I know what I don't know."

I know I know nothing about checking the innards of a boiler, and also that it IS required by French law to have your boiler checked every year by a "chauffigiste," which is something we've done for the 6 years since we've had this one, and which has always performed stellarly till now.
I was hoping to be able to wait till all this dusty, plastery work was done before calling them back, but I'm not sure it can wait.

To answer some questions anyway: It's Viessmann 200 Vitodens, which AFAIK is a fairly new model. Yes, it's a condensing boiler, the flue is concentric, and it's horizontal.

I've checked and checked again the seals of the flue, and they're really quite snug. It really does sound to me like an acoustic issue, but...
I'm now suspecting that the flue was full of construction dust and debris, and when I moved it all that junk slid into the system, and fouled things up? Could heaps of dust screw it up that badly?

At first I thought it was making that sound EVERY ignition, but I see now it's only during high load/heavy demand. Most of the time it's running silently, then when we do the dishes WHILE the heat is on, it goes into overdrive and "WHOOOSHHHHHHH wheee"!
Well, off to call in the big guns now, hope it won't set us back too much.
Thanks again for all your comments and concerns.
:thumbs up:

It sounds like the flue is not air tight , probably where it joins the boiler, when its running & making the noise try to put your hands round the joints if the sound changes that's your problem, or you have had the combustion chamber panel off & not re sealed it correctly, both dangerous situations,if you cant sort it get a pro in.

algas said:

It sounds like the flue is not air tight , probably where it joins the boiler, when its running & making the noise try to put your hands round the joints if the sound changes that's your problem, or you have had the combustion chamber panel off & not re sealed it correctly, both dangerous situations,if you cant sort it get a pro in.

Click to expand...

Yeah, I already tried that hand on the joints test, although not on the joint right at the boiler
As for the combustion chamber, I never opened it myself and don't plan on it! I did turn all the maximum temps down on the control panel last night, and that seemed to quite things down a bit, but def calling in a pro the next couple days, this stuff is way beyond my comfort zone.
I've also been leaving the window in the pantry (that's where the boiler is) open a crack 24/7, just in case!