Droning noise in central heating boiler

[purplefleece]

I have a Vaillant combination boiler about ten years old. Since having an expansion vessel fitted recently, the boiler makes a noise like a plane going over when the hot water is running.

The noise starts soon after the hot water is running and goes down in tone lasting up to thirty seconds, then there is a silent pause for a few seconds an it starts up again becomign louder and the cycle repeats until the tap is turned off and often the pipes make a one off bang at that point. I am not certain but I think the droning has also happened sometimes when the heating is on but rarely. It does not occur when running cold water or when running the hot tap when the boiler is turned off.

The plumber who fitted the expanson vessel suggested it was the fan and applied some WD40 but this has not worked.

I would appreciate any other ideas on the possible cause and solution to this problem. Thanks.

 

[purplefleece]

still hoping for ideas please..... sounds too scary to take showers here! thanks.

 

[joe-90]

The fan bearings are worn and it's starting to flutter. WD40 can't cure worn bearings, you need a replacement.

 

[purplefleece]

Thanks for reply. So this would happen just with hot water and not with central heating?

 

[joe-90]

The boiler works harder during hot water and the fan turns faster - hence the problem.

 

[45yearsagasman]

purplefleece, Mr 90 knows as much about boilers and heating systems as I know about brain surgery and astro physics.

 

[joe-90]

Would you like to help the OP Gasman?

 

[joe-90]

For the information of the OP:

A boiler is rated by its hot water output. In other words, when heating water it is flat out.

For heating purposes, this level of heat output isn't required, so it *modulates* according to an algorithm for economy.

If we were talking about your car at full speed on the M1 - then you may get wheel wobble due to a badly balanced tyre.

At lower speeds in a 40mph zone - then that effect may not happen.

The boiler fan is subject to the same rules of physics.

That's why you only notice the effect when the boiler is at full output.

 

[jj4091]

I'm not a heating engineer, but when we had what sounds like exactly the same problem on our Ideal boiler the secondary heat exchanger had to be replaced. Ours did not have a problem in heating mode as the secondary heat exchanger only feeds the hot water as far as I know.

 

[bengasman]

The boiler works harder during hot water and the fan turns faster - hence the problem.

Still don't have a clue, do you Joe.

This is probably the old Ecomax and the symptoms can have 4 different causes on that model; none of them diy territory.

 

[joe-90]

Not in this case. Let's hear your solution.

 

[bengasman]

Let's hear your solution.

Which part of:


none of them diy territory




don't you understand?

To work on an Ecomax, you need a fga plus certification to use it.

 

[joe-90]

Let's hear your solution.

Which part of:


none of them diy territory




don't you understand?

To work on an Ecomax, you need a fga plus certification to use it.

The OP isn't about to do any DIY work - hence they got an RGI in. Which bit of THAT don't you understand?

 

[bengasman]

The OP isn't about to do any DIY work - hence they got an RGI in. Which bit of THAT don't you understand?

1. The "plumber" spraying wd40 on the fan was almost certainly not a rgi.

2. If the OP was looking for a better heating engineer, he would ask where to find one instead of looking to find the solution himself, wouldn't he?

 

[joe-90]

Most people refer to RGIs as 'plumbers'.

The fact that he was in front of the boiler with the cover off listening - he could well have been a monkey and heard where the sound was coming from.

It was the FAN. Get over it and move on.