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

 

[iconboy2021]

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

thanks will show this thread to Baxi, when they come next week to have a look at it.

 

[Chuck]

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

Perhaps, but Megaflos claim to have an inlet diffuser to prevent this.

 

[ShaunCorbs]

Never seen one on the cut away models I’ve seen ?

 

[iconboy2021]

Perhaps, but Megaflos claim to have an inlet diffuser to prevent this.

Would a water damper valve help on the cold inlet, going in to the cylinder?

 

[Chuck]

Would a water damper valve help on the cold inlet, going in to the cylinder?

I doubt it, but I'm also not convinced that the cylinder is the root cause.

Plumbing carries sounds and I don't think you can assume that the noise originates inside the cylinder just because the emitted sound is loud near it.

 

[iconboy2021]

I doubt it, but I'm also not convinced that the cylinder is the root cause.

Plumbing carries sounds and I don't think you can assume that the noise originates inside the cylinder just because the emitted sound is loud near it.

thanks for your response.

The noise sounds as if its emitting from the bottom of the cylinder (where the coils are located) if its a hammer issue, then looking at this logically, the sound maybe emitting from the cold inlet, or the flow/return from - however the flow/returns are short runs - securely bolted in place - if the cold water is the culprit - then this securely fixed to the wall.

MDPE 25mm incoming downstairs directly under the eaves cupboard (1st floor) - mdpe stop valve then 22mm copper all the way to eaves - bull bore stop valve, then to megaflo blue stop valve + PRV frpm here its tee'd off the cylinder and rest of the house.

 

[iconboy2021]

This seems to be getting from bad to worse, the popping noise issue - which was limited to the hot water demand from the taps, is now happening towards the end of the DHW heating cycle. A few minutes before the boiler turns off and the cylinder has achieved it's preset temperature 60° then the popping noise begins, with intervals of 1 minute apart, this carries on until the 2 port valves kicks in, along with the bypass valve. the popping noise continues for a few minutes after until the boiler stops.

Baxi popped down during the week, and sods law, I could not demonstrate the popping noise. I've sent the engineer the recordings, I will chase up with Baxi in a few days time.

I've added an edited a recording of the popping nouse, from when the boiler is heating up the water, to when the 2 port valve kicks in.

 

[iconboy2021]

Hi all,

its been a while, anyways Baxi have agreed to replace & reinstall a new cylinder due to clunking + popping noise, which has got worse - the noise seem to happen randomly, even when I've not drawn any hot water or if the cylinder is not calling for hot water.

I would also like to take this opportunity to have have pipes sorted out too - can anyone recommend any optimisations?

I see that my install has a manual air bleed valve on the primary floor to cylinder cylinder, would I benefit from installing an automatic bottle type air valve and do I have too many 90° bends, would it make sense to have some of these removed.

I've also been advised to add an external expansion vessel too - perhaps this will reduce any future knocking noises too.

I welcome your thoughts.

 

[Davetoff]

Did this issue get resolved when Baxi replaced your cylinder?

 

[iconboy2021]

Did this issue get resolved when Baxi replaced your cylinder?

I have the replacement sitting downstairs (there was delay in sourcing a new cylinder) going have some amendments made to the pipework.
I have a manual air vent on the primary flow within the cylinder, going to replace this with a Honeywell auto air vent and I'm considering a Spirovent too, also going to have an external expansion vessel installed.Once thats done, I will call out Baxi to swap out the cylinder.

 

[Lou]

(Just bumping a few older threads, they will drop off what is new soon)

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