Boiler fan noise.

[Dave Plowman (News]

Recently fitted a new fan to my Viessmann 200w wb2b system boiler. Came from what I assume is the maker's spares place (Viessmann Direct).

Only noise the old made was the sound of air going through it. Only really noticeable if close to the boiler, and only then when it started up.

New one makes a whine. Which varies in pitch with its speed. At full speed near enough middle A in pitch.

When the boiler is firing, only just audible. But when firing up, the fan runs up to full speed before ignition, then ramps down. And the boiler does shut down totally once the call for heat is satisfied, so goes through this cycle frequently when not running flat out.

At speed, it's very audible in the rooms alongside where it is.

The new fan looked identical to the old, from the outside. Just wondering if I should complain or not?

[Fredxx]

Are the fan blades identical? Is it the motor or the fan making this whine?

Are the bearings of a ball race type? Some are. A faulty race can certainly make a whine, in which case I might expect imminent failure?

[Brian Gaff]

Could be out of balance or crap bearings. Is it a brushed motor? Brian

[Roger Mills]

Could something be bridging one of the rubber feet, and transmitting the motor noise to the casing?

[Brian]

Have you checked for ‘whistle effects’ - small holes that shouldn’t be there, ditto edges etc the air blows over, …. These can cause a whistle / whine as the air passes by.

A bit of silicone or epoxy does the trick.

[Max Demian]

I had a bathroom fan that became noisy after it was on for five minutes or so. Turned out the timer that cut it out a few minutes after turning the light out kept cutting it out when it shouldn't

[Chris Hogg]

My first shot at fixing anything like that is a drop of 3-in-1 on the bearings. Does the fan spin freely when not under power if you spin it by hand?

[Dave Plowman (News]

Don't think so. Given it a tap when running (it is on flexible mountings) and the noise doesn't alter.

[Dave Plowman (News]

It doesn't sound like dry bearings to me. The noise being entirely dependant on speed - and varying pretty uniformly. Dry bearings tend to screech and then go quiet - depending on speed.

It would require dismantling the unit to see if the fan spins freely. And I'd rather just get it exchanged for another. But the control side of the boiler seems to check it is at the right speed, and if not shows a fault.