steveoelliott

It reads 4 bar almost immediately after shutting tap off and stays there. Might be a bit more or less depending on time of day etc. it never really creeps up. It is a large 5 bed house with lots of outlets / 4 bathrooms so a big system to flow around.

Thanks. What’s the correct way to set the PRV though. With a tap open? And should I aim for static pressure at 2 bar? I think the issue is the static pressure at 4 bar despite it dropping to 2 bar static when tap open.

Yes the stop cock PRV is on the main and prior to the UVC PRV. It seems to be the rapid discharge from the EV that triggers this.

One at the main and one on UVC. It’s this that gives the balanced cold. They offered a UVC but I took the option of a boiler instead as I planned not to use a megaflo going forward to opt for another cylinder. The thing is I want to be certain it is the cylinder before swapping. Are you able to advise how I set the dynamic pressure on the PRV off the stop cock. Is it just open one outlet and set? The static is around 4 bar and between 1.8 and 2 bar when running. thanks again.

@Nickfromwales and @Mattg4321 - The PRV on the megaflow is fixed at 3 Bar (no adjustment on the BAXI one). However, the one on the incoming cold main is adjustable. Question is mine does not have a setting with pressures, rather you adjust it with water running and use the gauge. To find dynamic pressure, I figured this would be with one tap open but wondered what is the correct way to measure dynamic pressure. I read elsewhere that this noise is caused by the sudden rush of flow when you open a hot outlet propelled by the charge of the diaphragm in the vessel. In an ideal world we'd have a valve that allows water to fill the EV unencumbered but restricts it emptying. Not sure if such a valve exists.

This is a really good example of the problem but not my video.

Thanks @Mattg4321 my main concern was actually damaged or rupturing of pipe joints due to the vibration. in terms of what you did with your PRV, did you open a tap and then set the dynamic pressure to 2.5? In my case static is around 4 bar dropping to around 2 bar with a tap open. The more taps I open the lower dynamic goes naturally.

I’m also interested in the theory that the PRV should be set to the incoming mains pressure or marginally below but whether this means the static or dynamic pressure.

@Mattg4321 Thanks. Did you set the PRV for the cold main based on static or dynamic pressure? Also did you look at my post / watch the videos. Interested to see if what you saw was similar.

@Mattg4321 Did you ever get to the bottom of this issue? Was lowering the pressure to 1.5 bar your ultimate solution? I have an ongoing issue, not yet resolved here: The latest I've gathered is that EV pressure should be ~0.2 bar lower than dynamic pressure. But what is an accurate way to measure it. We are fortunate to have a gauge on the PRV at the stop cock. Is just opening up a tap enough to measure pressure? The thing is the pressure shown on the gauge will vary depending on the tap used / flow rate etc.

Hi, I have a decorator that has been working for me and I must say I am very impressed with his work and the way he works. He has spent a great deal of time on preparation that far surpasses anything I've seen before. The ceiling in my kitchen was finished yesterday and it previously had a long crack running the length of the ceiling between spotlights. There wouldn't be a joist here given that the spots are there so I don't think it's a case of a join in the plasterboard being responsible. Anyway, he raked this out deep and filled it. The whole ceiling was sanded / prepped and hoovered free of dust before painting in AR2. He left yesterday evening and said, he'd leave everything masked so he can snag it Monday and encouraged me to find anything wrong with it. That's a first for me! A trade asking me to snag! Anyway, I looked last night and I have to say it was flawless, I even got a flash light on it just trying to find something for a giggle and whilst with that I could find a couple of tiny things, there was really nothing at all. It was perfect. Anyway, this morning, that dam crack has come back. I just wonder what it might be and what the solution might be? Probably taping I guess. I will ask the guy Monday but I can't help feel bad given the amount of work he put in. Thanks...

Hi Folks, Our house has a bin store which was there from previous owners. It looks to me like it is some very fine MOT type stuff that has been leveled with the adjacent blocks and whacked. I would like to extend this further onto a muddy area behind it but am just wondering on the process / materials. Appreciate your help.

Whatever it is seems to change... sometimes it's not there at all, other times it's very quiet and other times it's loud like some of the videos on here.

Hi @Doug Tag So I will be swapping the cylinder at some point. However, we (my plumber did the work) did replace the EV and I set the pressure to 2.8 Bar before giving him the EV to install. The issue persisted. The dynamic pressure varies from 2-3 bar here. The EV we took off was at 1.95 bar when checked. The plumber also removed the NRV on the hot outlet from the top of the cylinder. The issue persisted so that I think rules out the EV. In addition, I am even able to replicate the noise with the inlet valve to the cylinder closed upon opening the taps. This now seems to happen every time a tap is opened but to a lesser degree following the first time after the heating cycle. I have heard elsewhere that the issue is likely to be internal to the cylinder, i.e. something come adrift or the old broken up baffle causing issues.

That sounds exactly like what my Megaflo is doing right now!

Baxi delivered the boiler to me personally on a pallet Friday. I was also shocked by this! A manufacturer supplying an end customer with a product that they have refused to fund to fit, it's a little unseemly to say the least but I have no intention of fitting it myself. It's not second hand, has all paperwork with it and my (or indeed any plumber) can activate the 10 year guarantee once installed. My own plumber does a lot of work for builders and reckons he can sell it on my behalf. Of course it will be less than book price but be mutually beneficial.

If you can recall where, please let me know.

They did but I don't want another Megaflo with a floating baffle that will only break down again in time. They offered a Combi, with Flue and Controls which I plan to sell to fund the cylinder swap.

Thanks. My plumber has suggested Gledhill. Not sure of the difference. Appreciate you sharing that!

Understood and this advice has been resounding which has changed my mind. I intend to stick with a UVC.

Baffle broken down and very loud noise deduced to be internal to vessel. Now not going for Combi but considered it for a while.

Current one is defective.

Baxi, current one baffle broken down and loud noises coming from cylinder. Yes on a DIY group but not exactly the same question, rather about whether a Combi would be a suitable replacement.

I currently have a Megaflo system with the built in air gap. I've been offered a replacement or the alternative of a 36KW combi, controls and flue. The later is worth a significant sum of money even if I opt to replace the cylinder off my own back and then sell the boiler etc. The question is, what cylinder should I purchase. I hear a lot of folks slating the Heatre Sadia megaflo and it's systemic issues with the air gap breaking down etc. I've been told that Gledhill are better. Any thoughts?

So not performed any calculations yet and our current system boiler (Vailant Ecotec 637) is running fine. It doesn't appear to cycle frequently and with a crude estimate (double yours), it isn't too far off the mark. Probably don't need bigger for the CH and you are likely correct that larger would be wasteful. There isn't a problem per se. Water pressure does fluctuate between 2-3 bar at different times of day. I have a PRV with gauge on the incoming main. If we run the bath tap on full then other water outlets are majorly impacted but the same also applies for cold but not completely unusable. The reason for the consideration of swap is owing to an issue with the UVC which Baxi have agreed to swap with either another UVC or Combi Boiler under warranty. I then thought having a combi would mean one less thing to maintain, service or have the potential of leaking. It is however clear that a combi boiler is going to be a downgrade in our performance. I have no issues currently but fear I could going with a combi. I appreciate all the helpful advice and guidance folks have given.