Clunking metal rattle noise ONLY first fire up

[Hkphooey]

Hi guys,

I have a Potterton FSB 30 HE.

I just had a major service. The boiler was completely taken apart, cleaned out, and all new seals and a new burner were installed.

Everything runs great. All the radiators are hot, and the boiler runs smoothly, except for what seems like the very first time it fires up the water or heating. It clangs and bangs like metal against metal for about 20 seconds.

The thing is, it doesn't do it all the time.

It didn't at the time of me writing this.

There is no noise once it's up and running.

I don't get any lockouts, but I'm worried that it's going to break somehow.

I've read about possible limescale buildup, but it doesn't do it all the time.

I have some Fernox F2 to put into the system via the radiator. I understand this helps with water tension and could help.

Is it possible to just treat the heat exchanger rather than do a power flush? I've heard a lot of people saying theirs is still banging after a power flush, and it was the limescale on the exchanger.

All thermostats and thermistors have been checked; the wiring seems fine, and the electrodes seem fine as they're new (6 months ago). The flue has also been checked.

 

[dilalio]

Is it pipework banging?

 

[Hkphooey]

Is it pipework banging?

No it's defo not pipework bud as far as I know....
I'm sure it's coming from the boiler.
Like I say it's not doing it all the time, imagine a fan is loose within a housing metal type noise.. banging type.
Really hard to pin point

 

[dilalio]

Have you spoken to whoever serviced it? Can't they come back and have a look/listen? I would be going back if it were a job I'd done... Even if it proves something unrelated!

 

[Hkphooey]

Have you spoken to whoever serviced it? Can't they come back and have a look/listen? I would be going back if it were a job I'd done... Even if it proves something unrelated!

They have been back but it's annoying ...
Another thing is it seems to NOT do it when temperatures outside are above 12 degrees like today.

Just want someone who's had similar as keep throwing money at it as seems gas engineers just want to keep replacing parts starting with cheapest until it solves it
BG said just change the boiler 4k

 

[dilalio]

They have been back but it's annoying ...
Another thing is it seems to NOT do it when temperatures outside are above 12 degrees like today.

Just want someone who's had similar as keep throwing money at it

Doubt you'll find someone with same issue as noises can be attributed to a number of things!
Now it's been cleaned, might be expansion but that's a guess at distance.

Can you video it and upload to YouTube then put a link here? Might get you somewhere?

 

[Hkphooey]

Doubt you'll find someone with same issue as noises can be attributed to a number of things!
Now it's been cleaned, might be expansion but that's a guess at distance.

Can you video it and upload to YouTube then put a link here? Might get you somewhere?

Cheers yes that's the plan I will upload it..
But it's pretty specific the issues hence the questions

 

[dilalio]

Cheers yes that's the plan I will upload it..
But it's pretty specific the issues hence the questions

Maybe the fan has something in it or catching on housing and when it warms up it stops binding?

 

[Hkphooey]

Maybe the fan has something in it or catching on housing and when it warms up it stops binding?

Yes was looked into but as mentioned no pcb error or lock out and all seems to be working fine.

The temperature outside thing surely would point to something in particular?

 

[martygturner]

Do you have a magnetic cleaner installed ?

Crud in the heat exchange can make quite a noise on startup sounds like a kettle banging when its limescale/ magnetite up. It could be the pump, taking a bit to get going if there is surprise surprise crud in the system.

As you have had a major service, crud would be my first port of call. If you are confident about draining the system and refilling, add some system cleaner...run, then drain down the system, refill with inhibitor.

You could check the plume, does lots of white smoke ( its condensation but...) get spat out in the first 5 minutes, that points to a restriction in the condensate drain, again as you have had a major service and the burner chamber was washed out did some rust or carbon foul the condensate pump on the boiler. As the boiler fires the excess moisture can make a racket for a while as its converted to steam and expelled.

But first off you paid for a service, which should have left the boiler in a better state than before, personally I wouldn't touch it and be onto the service engineer....

 

[Hkphooey]

Do you have a magnetic cleaner installed ?

Crud in the heat exchange can make quite a noise on startup sounds like a kettle banging when its limescale/ magnetite up. It could be the pump, taking a bit to get going if there is surprise surprise crud in the system.

As you have had a major service, crud would be my first port of call. If you are confident about draining the system and refilling, add some system cleaner...run, then drain down the system, refill with inhibitor.

You could check the plume, does lots of white smoke ( its condensation but...) get spat out in the first 5 minutes, that points to a restriction in the condensate drain, again as you have had a major service and the burner chamber was washed out did some rust or carbon foul the condensate pump on the boiler. As the boiler fires the excess moisture can make a racket for a while as its converted to steam and expelled.

But first off you paid for a service, which should have left the boiler in a better state than before, personally I wouldn't touch it and be onto the service engineer....

Many thanks for the insight no won't be doing anything just some ammunition to get back to the engineer with.

Seems they don't try anything unless its suggested

 

[Hkphooey]

Do you have a magnetic cleaner installed ?

Crud in the heat exchange can make quite a noise on startup sounds like a kettle banging when its limescale/ magnetite up. It could be the pump, taking a bit to get going if there is surprise surprise crud in the system.

As you have had a major service, crud would be my first port of call. If you are confident about draining the system and refilling, add some system cleaner...run, then drain down the system, refill with inhibitor.

You could check the plume, does lots of white smoke ( its condensation but...) get spat out in the first 5 minutes, that points to a restriction in the condensate drain, again as you have had a major service and the burner chamber was washed out did some rust or carbon foul the condensate pump on the boiler. As the boiler fires the excess moisture can make a racket for a while as its converted to steam and expelled.

But first off you paid for a service, which should have left the boiler in a better state than before, personally I wouldn't touch it and be onto the service engineer....

Another thing is all rads heat quick not cold spots...so crud in system wasn't something we we're considering

 

[dilalio]

The temperature outside thing surely would point to something in particular?

Only that the boiler starts from a colder temp or colder air is drawn in.

Boiler fires because it's told to, whatever the outside temp.

 

[martygturner]

Only that the boiler starts from a colder temp or colder air is drawn in.

Boiler fires because it's told to, whatever the outside temp.

Yep...and at a colder temp and crud will have re settled and any failure to for the boiler drain properly will be exacerbated by condensation..

 

[Hkphooey]

Yep...and at a colder temp and crud will have re settled and any failure to for the boiler drain properly will be exacerbated by condensation..

Cheers guys gonna flush heat exchanger it's sounding like lime scale build up using fernox ds40