Clunk and scraping noise

[lotstolearndiy]

I have a Glowworm Swiftflow 100 combi boiler. It makes a loud clunk and scraping noise, on average about once or twice a day. I have uploaded it to YouTube. The sound I am talking about starts about 20s into the recording, but I have left the preceeding boiler noises in the recording to help with diagnosis. After the noise, the boiler fires up on full flame.
Can anyone tell me what the noise is?
Thank you

 

[easyflow]

Sounds like somthing stuck in the fan/impeller distorted.

 

[lotstolearndiy]

I'm sorry - I really don't understand your sentence. What do you mean?
Thanks

 

[onecog]

he said


"Sounds like somthing stuck in the fan/impeller distorted"




The birds are nesting early this year.

 

[lotstolearndiy]

Easyflow
I am going to respond further to you in the hope that you are more kind than onecog, who finds it difficult to tolerate my lack of intelligence.

When you wrote fan/impeller, it seemed to me like you were saying that they were the same thing. So I was reading it as "Sounds like something stuck in the fan distorted", which doesn't make any sense.
Is the impeller actually what is inside the pump? So, are you saying that it could either be as a result of something stuck in the fan OR as a result of the impeller being distorted?

 

[onecog]

The impeller is what spins inside of the fan and he said that it sounds like there is something stuck in the fan or that the impeller is distorted.
To me it sounded like someone had let the venetian blind up and down rapidly.

 

[easyflow]

Sorry what I mean is the fan that draws the boiler fumes sounds like it has somthing stuck between the impeller and the fan casing or the fan/impeller is distorted or fixings have come loose causing the fan to strike the cowling.

 

[doitall]

But it works fine for hot water.

 

[lotstolearndiy]

I could certainly imagine the fan being responsible for the noise...but I am surprised that it would run quietly all day and just make this noise only
once or twice a day.

 

[easyflow]

I could certainly imagine the fan being responsible for the noise...but I am surprised that it would run quietly all day and just make this noise only
once or twice a day.

The fan runs at different speeds so when it needs to expel more quickly it will run faster and run slower for less need to expel, my guess that from time to time the fan is striking the cowling or an obstruction between the fan and cowling.

 

[lotstolearndiy]

I thought I should post to complete the thread. The clunk and scraping noises were caused by kettling. The flow switch was faulty and caused the kettling. No fan replacement was required.

 

[45yearsagasman]

The flow switch was faulty and caused the kettling.

Never had that before, that a flow switch that can cause kettling.