Megaflo installation improvements?

[iconboy2021]

Hello,

I've previously created a thread about my Megaflo issues in the past, Baxi have agreed to replace the cylinder as an appliance change under warranty. May I ask if you you guys can have a look at my install and recommend any optimisations, prior to Baxi installing the new cylinder.

I do feel a little cynical as this will be the 3rd time its being changed, due to same knocking noise as before.

As always thanks in advance.

 

[EvilDrPorkChop]

Knocking noise?

I'm surprised you've got Baxi to replace the first time around, never mind a second! They usually aren't interested with MegaFlo issues in my experience.

 

[iconboy2021]

Knocking noise?

I'm surprised you've got Baxi to replace the first time around, never mind a second! They usually aren't interested with MegaFlo issues in my experience.

Baxi seem to be under the impression, that they have never come across this issue ever according to their customer services team 🤫

 

[iconboy2021]

Just had Thames Water to measure Pressure and flow rate, from outside (granted we would loose a bit at the cylinder)

Standing pressure - 4.1 bar
Dynamic pressure - 3.9 bar
Flow rate >25 litres per min


Stumped on why, we have the knocking noise: Megaflo clunking noise, drawing hot water. - https://www.plumbersforums.net/threads/megaflo-clunking-noise-drawing-hot-water.124210/#post-1141187

 

[SJB060685]

Banging noise when you open the hot tap?

 

[iconboy2021]

Banging noise when you open the hot tap?

Yes it is like a popping/knocking noise, its not hammer in the pipes - as we have had it all checked out - sound likes the cylinder expanding/contracting - as the same noise is also heard a few mins after the hot water tap is no longer running.

 

[SJB060685]

I’ve experienced similar on unvented cylinders with an external expansion vessel on a flexible hose. When the hot tap opens there’s a sudden drop in pressure and the charged vessel diaphragm creates a knocking sort of shock wave. Haven’t come across that on a Megaflow though.

 

[iconboy2021]

I’ve experienced similar on unvented cylinders with an external expansion vessel on a flexible hose. When the hot tap opens there’s a sudden drop in pressure and the charged vessel diaphragm creates a knocking sort of shock wave. Haven’t come across that on a Megaflow though.

Baxi are somewhat confused too.

 

[ShaunCorbs]

It’s every time you open the tap ?

 

[EvilDrPorkChop]

Have they not suggested allowing for cold water expansion before your pressure reducing valve? Seeming you have high pressures, plus is there any draw off before the pressure reducing valve and balanced colds (E.g. Kitchen tap)

 

[Chuck]

Was the PRV replaced at the same time as the cylinder? I've known them to be a bit noisy.

 

[iconboy2021]

It’s every time you open the tap ?

not always.

 

[iconboy2021]

Have they not suggested allowing for cold water expansion before your pressure reducing valve? Seeming you have high pressures, plus is there any draw off before the pressure reducing valve and balanced colds (E.g. Kitchen tap)

cold inlet, feeds right up towards the cylinder before it's balanced out, so no draw off beforehand, Baxi have not suggested anything about allowing for expansion before the pressure reducing valve - This is something I need to look into

 

[iconboy2021]

Was the PRV replaced at the same time as the cylinder? I've known them to be a bit noisy.

Baxi replaced everything, once they did the new appliance change over.

 

[iconboy2021]

It’s every time you open the tap ?

the popping/knocking noise, also happens when the boiler is heating the hot water in the cylinder, every 2 to 3 mins.

 

[IND_Nick]

Regarding the installation, it looks pretty decent to be fair, especially in such a tight space. My only criticism would be all the pipework could do with insulating, especially dhw and heating.
The knocking does sound odd, I'm not convinced a new cylinder is the answer but sounds like you've tried everything else so fingers crossed for you.

 

[iconboy2021]

Regarding the installation, it looks pretty decent to be fair, especially in such a tight space. My only criticism would be all the pipework could do with insulating, especially dhw and heating.
The knocking does sound odd, I'm not convinced a new cylinder is the answer but sounds like you've tried everything else so fingers crossed for you.

We have looked at everything, we just cant determine what the root cause is, another poster has mentioned about allowing for expansion before the PRV.

Does anyone have any links, to any expansion type devices or are we talking about an external vessel? (I don't think I have even had room to fit one, in that space) - I will speak to Baxi's tech team.

Thanks in advance.