baxi duotec combi 24he boiler, loud high pitched humming, whining noise.

[jonbbb]

Hello
I have an 8yo old baxi duotec combi 24he boiler.
When the gas central heating is running, it makes a constant loud high pitched humming/whinning noise.
The noise only quietens for about 5 seconds, each time the boiler reignites to heat the radiator water. Before then returning to the same level.


I am in the room above the boiler, the noise is quite loud and its persistence gives me ringing ears.
[see the link to hear the noise, recorded upstairs. the recording does not capture how loud the note is, only its tone ].
https://drive.google.com/file/d/0B2It1xwGdQ1IX012T1FXYVJLb1E/view?usp=sharing


Further info,
If the central heating is off, but the hot water tap is turned on. The boiler makes the same sound but at a much quieter level.

the diverter valve?* was replaced last week, but the noise is still there.
*Im sure the engineer said he replaced the diverter valve, after I also said that when the hot water tap is turned on for over five minutes, the radiators would fill with warm water.


--
My questions:
1. What is the noise likely to be coming from in the boiler? [or where has similar noise come from in other related boilers]
2. And when I call out the baxi engineer again, to attempt to identify the noise source. What are the likely parts, where they should first start their fault finding?


Thanks
Jon

 

[jonbbb]

edit:
"The noise only quietens for about 5 seconds, each time the boiler reignites to heat the radiator water. Before then returning to the same level."

should be
"The tone lowers for about 5 seconds, each time the boiler reignites to heat the radiator water. Before then returning to the same level."

 

[Dotty]

And for which you need a gsr to look at it. Let him do his job. It's what you'll be paying him for.

Job 38.11