Loud noise from Worcester-Bosch Greenstar 24i combi boiler - only heating

[JoeH10]

Hi all,

My Worcester Bosch Greenstar 24i combi boiler has recently started to make a very loud buzzing / drone noise, usually within about 5 minutes to 1 hour after the heating has turned on.

The problem only seems to happen when calling for heating, it has never happened when using hot water (e.g. while taking a long shower). After the buzzing starts, turning the heating off from my Tado thermostat gets rid of the noise. But next time you switch it on the problem will eventually reoccur.

Boiler was last serviced in April 2023 and I have checked the pressure is ok (slightly above 1.5 bar when heating is on)

I have a video for reference so you can hear the sound: https://drive.google.com/file/d/1eaYMpi4KvBTgPrV24SmqtO8vr5RFDqJo/preview

Has anyone had a similar problem? Or any experts able to suggest which part might be at fault here?

Thanks in advance.

 

[MagicDoughnut]

Probably the pump, hot water runs off mains pressure and the pump only kicks in for CH.

 

[ianmcd]

It is ca

Hi all,

My Worcester Bosch Greenstar 24i combi boiler has recently started to make a very loud buzzing / drone noise, usually within about 5 minutes to 1 hour after the heating has turned on.

The problem only seems to happen when calling for heating, it has never happened when using hot water (e.g. while taking a long shower). After the buzzing starts, turning the heating off from my Tado thermostat gets rid of the noise. But next time you switch it on the problem will eventually reoccur.

Boiler was last serviced in April 2023 and I have checked the pressure is ok (slightly above 1.5 bar when heating is on)

I have a video for reference so you can hear the sound: https://drive.google.com/file/d/1eaYMpi4KvBTgPrV24SmqtO8vr5RFDqJo/preview

Has anyone had a similar problem? Or any experts able to suggest which part might be at fault here?

Thanks in advance.

your boiler is what is called resonating, it is a combustion problem because it hasnt been serviced properly or the gas valve settings have drifted, get Worceter out direct to service the boiler properly

 

[MagicDoughnut]

It is ca

your boiler is what is called resonating, it is a combustion problem because it hasnt been serviced properly or the gas valve settings have drifted, get Worceter out direct to service the boiler properly

If it's a combustion problem why is it only present during the CH cycle and not during the HW too? (genuine question)

 

[ianmcd]

If it's a combustion problem why is it only present during the CH cycle and not during the HW too? (genuine question)

You have a combi boiler, when running HW the energy from the boiler goes to what is called a plate heat exchanger and that energy is used up quickly, so the boiler seldom modulates (reduces the burning rate) but when on CH once the radiators get hot the boiler will modulate to low rate just to keep them warm, and that is why you are getting the problem you have, when at low rate the burner is resonating, or think it of flame lift off as the mixture is wrong and that is the noise you are hearing, and that is why it only occurs when the heating has been on for a bit and the radiators are getting up to temp

 

[MagicDoughnut]

You have a combi boiler, when running HW the energy from the boiler goes to what is called a plate heat exchanger and that energy is used up quickly, so the boiler seldom modulates (reduces the burning rate) but when on CH once the radiators get hot the boiler will modulate to low rate just to keep them warm, and that is why you are getting the problem you have, when at low rate the burner is resonating, or think it of flame lift off as the mixture is wrong and that is the noise you are hearing, and that is why it only occurs when the heating has been on for a bit and the radiators are getting up to temp

That makes sense, thanks, appreciate it.

 

[Madrab]

the pump only kicks in for CH.

'Fraid not - this boiler has a main and plate HEX and a diverter valve, when there's a call for HW the diverter opens to the plate and the pump runs the heated water from the main HEX through the plate HEX, heating the cold water.