Megaflo clunking noise, drawing hot water.

[iconboy2021]

Hello, Hope you guys can help, I have a conk/clunk noise coming out the cylinder, when I draw hot water from any tap in the house - I’ve checked the pipes and I’m very sure its not water hammer, I will attached couple of recordings to the this post and what my setup looks like.

The cylinder is a Megaflo which is a warranty replacement from Baxi as the old one was make the same noise every minute or so whenever the boiler was heating the water, that noise was coming from within the cylinder too, some sort of expansion issue.
Baxi have been called out, and I’ve requested that they send out an senior engineer to troubleshoot this, as they have installed this unit. The noise doesn’t happen all the time and its not a loud crashing noise, its more of a metallic clunk noise however it seems more prevalent at night or when the cylinder has not been in use for a while.
I’ve regenerated the cylinder, however its made no difference, the cold water is balanced as the mains water is fed directly to the PRV and from here its and tee’ed off to the cylinder and rest f the taps. Whilst I wait for Baxi, any insights into this would be most useful, it would be sods law, to think that this unit is also faulty [like the 1st].

Thanks in advance.

 

[Chuck]

To me, that sounds like the outlet pipe expanding (slip-stick noise) as it heats / cools. I'd look at how the outlet is clamped.

 

[Radian]

Could it be an internal coil? Our Gledhill cylinder sometime makes a similar noise that I put down to movement in the corrugated tube wired to a former. It happens whenever its zone valve opens and closes.

 

[iconboy2021]

Could be however I dont hear this noise when the zone valve opens or closes.

 

[iconboy2021]

many thanks for your responses

 

[iconboy2021]

many thanks for your responses

 

[iconboy2021]

@Chuck the hot water pipe (from cylinder) does go though a brick wall, could this be the issue - hot pipe rubbing against wall as it expands or cools down? I have stuffed a bit of felt around the cavity, perhaps I need to secure the pipe further to wall, just before it enters the cavity. I will also lag the pipe to prevent contracting - will this help?

 

[iconboy2021]

Also inspecting the hot water pipe coming out of the cylinder - Could the double ended compression be the culprit? - the compression was added by Baxi after swapping out the cylinder, they had to cut the pipe out, should they have re-soldered pipe back in?

 

[iconboy2021]

Could it be an internal coil? Our Gledhill cylinder sometime makes a similar noise that I put down to movement in the corrugated tube wired to a former. It happens whenever its zone valve opens and closes.

View attachment 66813

Had some spare time this afternoon, to better understand the issue I'm facing, so got up close to the cylinder had mrs draw hot water from the downstairs kitchen tap and clunk! - the noise came of the bottom of the cylinder where I'd imagine the coils are located. I say this as after the clunk you can faintly hear the coil vibrate.

Baxi, will need to sort this out, what are the odds of getting another defective unit?1?!

 

[Radian]

I very much doubt that the manufacturer would consider this to be a fault and I would expect all their cylinders to do the same. You can see the way the coils are 'strung' in the cut-away picture. The brazed-in solid wall copper coils of yesteryear won't wobble about like these which may be shaping your expectations. I sympathise with you however.

Edit: Here's another instance

 

[iconboy2021]

thanks for your response, this can't be right. is it contraction in the coils?

 

[ShaunCorbs]

Try shutting the blue lever valve eg 1/4 the way shut

 

[iconboy2021]

Try shutting the blue lever valve eg 1/4 the way shut

thanks will try that and monitor foor the next couple of days - would this not restrict the flow-rate?

 

[iconboy2021]

@ShaunCorbs - a quarter turn on the blue lever has dampened the noise, from my initial checking, I will monitor over the next few days and feed this back to Baxi, when they arrive next week. Could this be a faulty valve?

 

[ShaunCorbs]

Sounds like you have high flow with the mega flows the cold inlet tube is kicked down so it’s hitting the bottom hard and either that’s your noise or it’s travelling / flowing up and vibrating the coil