Baxi low frequency hum

[pejoli]

Continuing my run of issues with a new combi installation four weeks ago, here's problem number 2:

I get an occasional loud (here-it-downstairs-in-the-front-room-loud!) low frequency hum (not quite subsonic, but pretty low) from the boiler (Baxi duotec 40) when the boiler is firing.

The easiest way to trigger it is to have the CH on, and run the hot tap for 4-5 secs - this switches the heat off (HW set at a lower temp of 45) and then it comes back on again and the temp climbs back up to the HW temp (set at 60), with the accompanying noise. as it reached 60, the note rises in frequency before cutting off with the boiler. It was also less frequently happens on its own as the CH is running.

Installer looked at it - only problem he could find was gas rate was over what is should be (22 rather than 20), and told us to call out Baxi. They are coming round on Friday.

Questions:

1 - Should I expect or insist the installer also attends when Baxi are here - what if Baxi says it's an installation problem? Will I be left in the middle relaying information?

2 - Anyone encountered this in the past, and have their own thoughts on what might be causing it?

 

[pejoli]

Well, the man from Baxi came round on Friday, and more bad news.

The noise is due to the gas pressure being too low. The standing pressure of gas is 22mbar but drops down to 13 when boiler running and 12 if using gas hobs – it should run at about 20 and the min. is 17mbar. He said he would have to switch the boiler off if it were much worse.
There is not enough gas reaching the boiler – the installer should have verified the working pressure – i.e there is an undersized gas supply.
We need to upgrade pipes from entry into house to boiler to 28mm, and then reset the CO2 ratios. He also said resetting the ratios is the installer's job.

Still, on the plus side, if we're getting the gas pipes replaced, I suppose we can also get the cold water pipes done at the same time (see my other posts).

Now to go back to the installer - any thoughts on what is reasonable to expect him to do?

 

[twgas]

Not saying the Baxi bloke is wrong, but did he check the working pressure at the meter, if it drops there, the gas supplier needs to be informed to sort it.

 

[pejoli]

Yes - he checked at both the boiler and the meter, so I assume he considered that.

 

[Agile]

I really dont think your installer can be gas registered!

We have to go throught a lot of training about gas pressures. Yours has not bothered to do anything about the gas supply pressure, was unable to measure it and thought the pressure in the boiler was too high but did not know what to do about it anyway.

Did you do any checks on his registration? You should be able to get him to return much of the money you have paid him so that you can get a registered person to upgrade the gas pipes and commission the boiler properly.

You can make a complaint to Gas Safe and they will make a free inspection to assess the situation, call them on 0800 408 5500.

Tony