Boiler suddenly humming

pieroabcd

Hi,
a few minutes ago I heard that the boiler suddenly started to hum, as in the audio file attached.
I turned it off manually, let it cool off for a few minutes and turned on again, but as soon as the thermostat turned it on it hummed again (when I recorded this audio file).
Now it's more or less working as usual, but every now and then I can hear a short humming sound (1 second).

What can be the cause? Do I need to call an engineer?
This is the recording https://drive.google.com/file/d/15kqVqoB8A225mRMNeKBlfN3Yi4Yc7KCp/view?usp=sharing

Thanks.

ThisIsWeird

Combi boiler or Heat-Only/ System type? Make and model?

No idea, but it sounds like a motor bearing, so that would point at the main combustion fan, or the circulating pump.

If it's a combi, what noise does it do when you turn on a hot tap?

pieroabcd

It's combi.
No special noise, the usual continuous noise that of a boiler that turns on

TELLIT01

It's probably the pump.  Ours does the same.

ThisIsWeird

If it's a combi, then the combustion fan would fire up to max speed when delivering DHW, so I'd expect the hum to change very obviously too, if that was the culprit.
That pretty much leaves the circ pump as the only other constant noise generator, so likely as Telling says.
If it works, then fine. If the noise dramatically changes, then...

pieroabcd

Ok. I'll give an ear.
I wonder how much it costs to have the pump replaced iif it comes to that.

Thanks

ThisIsWeird

Make and model? Labour should be cheap, so the main cost will be the pump itself.
I'd sit on it until it becomes noticeably worse. 

pieroabcd

A very popular Vailant ecotec plus 837

ThisIsWeird

pieroabcd said:

A very popular Vailant ecotec plus 837

Looks like ballpark of £65 for a reconditioned item (and these are usually to 'as new') or more like £120 upwards for brand new.

Provided access is good, it looks like a doddle to replace.

pieroabcd

Considering the price difference, probably it's not the case to be cheap.

FreeBear

ThisIsWeird said:

pieroabcd said:

A very popular Vailant ecotec plus 837

Looks like ballpark of £65 for a reconditioned item (and these are usually to 'as new') or more like £120 upwards for brand new.

Provided access is good, it looks like a doddle to replace.

A combi boiler, so the pump will be inside the main casing. To remove the casing, you need to be Gas Safe registered (yes, it sucks, but....). So unfortunately, this means paying standard GS engineers rates.

How old is the boiler, and is it still under warranty ?

If it is under warranty, you need a qualified GS engineer to do the replacement, and you may well get it done under guarantee - Check with Vaillant before doing anything yourself.