Hi all,

I hope once again you can help me...

I got a Baxi DuoTec 28 Combi boiler.
Recently it started to make some strange noise sounds like humming or vibrating, but quite loud. you can hear it in the whole house (maybe because the noise alse travel trough the pipes?!).

Today I opened the front cover to have a closer look at the source at the noise but I'm not sure... From the outside it would sound like the pump, but after opening it sounds more like the noise is coming from the upper part which has another cover in front of it (which i don't want to open...).

Also I noticed that the pump is burning hot, is this normal?

I'm also fairly sure it has to do with the heating part of the boiler because as soon as you open a hot water tap the noise stops and return when you close the tap.

Also the noise is not there all the time sometimes it stops for a few minutes and the comes back, but i can still hear the water in the heating flowing, so i think the pump is still on.

I checked that both automatic air vents are open and also tried to bleed the pump with the big screw, but it doesn't make a big difference.

Last point is that I seem to get some air into the system from somewhere... I need to bleed the bathroom radiator every few days.


Sorry for this long story, but i wanted to provide as much information as possible...

Any ideas what could be the problem?

Thanks!
diyoptimist

Have a look on page 12 fig 7 are both fittings installed

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Hi Scruff,

about which page 12 are you talking?
The Installation instruction on page 12 have no figures...
Figure 7 on page 14 is a schematic and doesn't show 2 fittings.
The User Manual has also nothing on page 12.


Please let me know where to look and i will happily answer

Thanks
diyoptimist

A check valve and shock absorber.

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There is a check valve in the filling loop.
Definately nothing else in the pipe work of the CH system.
THere might be something build into the boiler thought...

Fig 7 clearly shows a check valve and expansion vessel on the mains, not saying that will cure the problem, which could be a design, installation fault.

You need to sort the leak out sooner than later as well.

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Scruff

Which fig7 are you refering too?
I can't find this fig7. Also which leak??

On the incoming mains, where it tees off to the boiler.

You have a problem with air in the towel rail, therefore you have a leak, assuming the system has been in for more than a few weeks.

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I have checked all the visible pipes and can't see a leak anywhere.

That might be a stupid questions, but why would i get air in the bathromo rad if i have a leak on the incoming mains?

Two separate issues.

You have two problems, the first is vibration, the seconds in air in the towel rail.

How old is the boiler, and can you get the installer back.

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The boiler is brand new, maybe 6month old.

But getting the installer back is not an option... he was very unreliable and i don't want him back in the house...

when you are refering to the different fig and pages, at what document are you looking at?

The installation manual, it maybe page 14 and not 12 as I said, but fig 7 should be the same.

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ok, i checked the maual and looked again at the figure.

The check valve is integral part of the filling loop.
There is no expansion vessel or pressure reducing valve outside the boiler.
But as far as i know there is a expansion vessel build into the boiler.

Also the diagram refers as far as i can see to the hot water part...

But i only have the problem with the heating part.
As soon as the hot water is used the noise stoppes (if there is any noise...)

Today i can't hear anything... i'm really not sure what is causing it.
It sounds a bit liek an old CPU fan in a computer, just louder.

http://www.baxi.co.uk/baxiduoteccombi

Download the installation guide, it takes a while.

6.0 System details on page 14.

Fig 7 shows a check valve and expansion vessel on the mains cold to the boiler.

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thats what i just looked at

please forgive my ignorance, but how would the absence of the check valve and expansion vessel create this noise?

As far as i can see the check valve is only there to prevent pollution of the cold water, isn't it? The old boiler didn't have this and the new boiler is now just on an extension of the cold water pipe from the old boiler location.

Also because this cold water pipe run is quite long (goes all the way to the loft across the house and back down) i thought there should be enough opportunity for the water to expand back if needed, right?