Boiler noise

[stuuk]

Hi Guys

I hope someone can help me with this boiler noise.

Everytime my boiler gets close to the cut off temp on the main boiler thermostat it starts making a noise like an airliner going past until it cuts off. When the boiler fires up again it runs for a couple of minutes without the noise then makes the noise again for a minute or more until it cuts off again.
The noise is like a medium pitched hum that sounds like it is slowly decreasing in frequency until the boiler turns off.

The noise definately seems to be coming from the boiler but it does resonate through the main boiler pipes.

Thanks

Stu

 

[Fluffster]

Sounds like you may have a limescaled heat exchanger.

Pete

 

[stuuk]

If this is the case whats the easiest way to fix it?

thanks

 

[tryitandsee]

.....or pump not circulating water through quick enough.

More information as to what boiler, combi or heat only etc. would help.

 

[stuuk]

The boiler is a Glowworm Fuel saver MkII
It's not a Combi boiler

I suspected the pump a year or so ago but replacing it didnt really help and the noise seems to stay the same on the high or medium speed setting

 

[namsag]

stick some sentinel x200 or fernox boiler silencer in it .
Feulsavers can also sound like this if they are over gassed

 

[stuuk]

Ok i'll try that but here's some more info

If I adjust the speed of the CH pump while the humming is occurring the humming changes pitch
Its a higher pitch with the higher pump speed.

If i turn the hot water tank thermostat up while the noise is there it disapears ie i divert the the pump through the HW tank rather than the radiators

In summary then

The noise only starts when the boiler is up to temperature
The noise is like a medium to high pitched hum that can be heard everywhere in the house.
When the boiler thermostat cuts out and the burners turn off the noise disappears
The noise starts quitely gradually getting louder and falling in pitch until the boiler burners cut off. When the burners turn on again after a minute or so the noise starts again.
The whole cycle repeats every few minutes.
Increasing the CH pump speed increases the pitch of the hum.
Diverting through the HW tank stops the noise all together

Thanks

Stu

 

[ambi]

Have you got an auto by-pass valve fitted?
If not it may be the answer.
Regards

 

[stuuk]

The only automated valve is the valve that diverts the boiler water to the radiators or the hotwater tank.
This is controlled by the strap on thermostat on the hotwater tank

 

[Agile]

Have you got TRVs on the rads? If so open one of them fully.

Have you tried turning down the boiler stat?

Can you measure the flow temperature from the boiler? You may have it set too high.

Is there a very big difference between the flow and the return at the boiler when on heating?

What is the colour of the water if you belld a little out of a rad air bleed screw?

Tony

 

[Ronald0]

"Diverting through the HW tank stops the noise all together "

Does the noise stop with HW on only; CH off?

If so, as boiler and pump are running with no noise, problem must be in CH circuit. Resonance and/or partial blockage in radiators or pipework.