Vibration when first opening hot tap after u/v cylinder heating cycle

[nashant]

Hi all. As the title says, I have a problem with an unvented cylinder I had installed last year where the first time I turn a hot tap on after the cylinder has been heated I get what sounds like a vibration. It generally starts about 1s after I open the tap and lasts for about 1.5s. I've attached a recording, the start of the recording is when the tap is opened.

This problem has been ongoing from the start but seems to have gotten worse in the last 6 months. The company that did the install don't seem to have a clue and now are pretty much trying to wash their hands of the situation.

A bit about the system...

ATAG i32s boiler in the kitchen, primary flow and return go up to the cylinder in the loft, about 13m away before coming back down on another 8m run before they tee off for any rads (is this normal? Means that hot water has to travel over 20m, and up through the unheated loft before seeing a rad).

250l Joule Cyclone Plus in the loft, with Caleffi valve set to 3 bar, and 19l expansion vessel. One side of the valve has cold main on top and balanced cold on bottom, other side has EV on top with cylinder feed on bottom.

Flow rate to unrestricted tap straight off main is about 18l/min.

Pressure on main is about 4 bar, rises to 5 bar after a heating cycle on the cylinder.

Pressure on the hot is 3 bar normally, rises to 4 bar after a heating cycle.

Sure there's some information I've left out, if so please do tell me.


Any suggestions would be so gratefully received, got a whole house renovation to project plan before January, a new baby to take care of, and a day job to do. Could really have done with not having to think about this!

 

[SimonG]

G3 engineer to look at it, pretty basic stuff to be honest.

 

[nashant]

I had g3 engineers install the thing and keep coming back to look at it, all to no avail. That's why I'm hoping to get some advice here. I'm not trying to actually do the work myself, but just trying to get informed enough to a) not get the run about for 6 months yet again, and b) not get my pants pulled down on the price for a fix.

Hoping that someone out there has heard this sound before and has an idea what it probably is.

 

[SimonG]

Like I said, you need a g3 engineer. Easy fix for a competent and experienced person. Especially with the detail you gave in your original post.

 

[nashant]

Like I said, you need a g3 engineer. Easy fix for a competent and experienced person. Especially with the detail you gave in your original post.

I'm absolutely gonna get a g3 engineer to fix it, I'm just hoping avoid getting another engineer in and finding that they too can't fix the issue. If someone here says "oh I know that noise, it sounds just like x is happening to x" then I can ask a local engineer what they think and if it marries up then happy days, I can get them in and move on with my life. If, however, they say something that the general consensus here is that it's definitely not then I can talk to a different local engineer.

I've had 3 people from the company who originally installed the system come and look at it, all they've done is fit some pressure gauges on the main and hot, wedge some pipes in a few places, and fit a PRV to the main saying to try turning it down and up and see if it makes a difference. As you can imagine, I'm quite disillusioned and am trying to gather as much information as I can in order to be able to make an informed decision about who I pay more money to. It would seem that not all g3 engineers are equally competent, I'm trying to avoid more people just taking my money and then buggering off.

 

[Chuck]

There's one thing that it might be that can be tackled by a diyer. Megaflos have a trapped 'bubble' at the top of the cylinder that acts as an expansion chamber. When this runs out you get dripping at the tundish during heating and, sometimes, the sort of fog-horn noise you have when the HW tap is opened.

There are step-by-step instructions for replenishing this in the instruction book. My tip is to wear a gardening glove when holding the spring loaded valve open. It's got a fairly strong spring on it and nasty sharp knurling on the grip. Allow about 15 minutes to drain out enough water enough to completely replenish the air chamber.

If that doesn't fix it, try contacting Megaflo customer service. They will be able to send their own guys or refer you to someone who knows what they are doing.

 

[nashant]

It's actually a Joule horizontal Cyclone Plus I've got

 

[Chuck]

It's actually a Joule horizontal Cyclone Plus I've got

Sorry, please ignore my reply then. (I seem to have been reading two threads at the same time, curse this tabbed browsing!)

 

[fowlerboi]

I'm pretty confident it will be something to do with the expansion vessel and pressure reducing valve on the multi function.

I would be checking to ensure the pressure reducing is set to 3bar, the expansion vessel is 3 bar also and the expansion vessel is sized correctly for the system.

 

[nashant]

Another data point! The kitchen tap, which is old and has no follow limiter has about 1 second of flow until the noise starts. The bathroom tap which does have a flow limiter on it takes quite a bit longer before the noise starts. And the noise only starts at the end of the burst of extra pressure from the EV emptying.

I've bought a 35l Zilmet Hydro-Pro and am getting an engineer recommended by a friend to fit it.

Is there a chance it could be the spring in the check valve on the combi returning to position? If the EV replacement doesn't do it then I'll get them to replace the combi. Can one not have a combi and instead have the separate components? Is there a benefit to that?

 

[ShaunCorbs]

Why are you getting a second expansion vessel fitted

 

[nashant]

Why are you getting a second expansion vessel fitted

Not second, replacement

 

[ShaunCorbs]

No issue with the expansion vessel also 35l you have a 400l unvented ?

 

[nashant]

What makes you say no issue with the EV? There has to be something making that noise, and one of the theories so far has been EV diaphragm reverberation. I'm pulling my hair out and have been abandoned by the company I paid £13k for a complete repipe of heating and hot water. I'm at a point where I'm willing to spend a few hundred quid just trying stuff, it's driving me mad

 

[ShaunCorbs]

Are the pressures equal in regards to ex and cold water - .2 bar

 

[nashant]

Are the pressures equal in regards to ex and cold water - .2 bar

The main varies between 4 and 5 bar over summer, it's dropped to 3 to 4 currently. Assuming Thames Water's winter pressure level. The pressure on the combi is set to 3, this is confirmed (I think) by the pressure on the hot being 3 bar at all times apart from immediately after a heating cycle. After a heating cycle the pressure on the hot rises to 4 bar. The EV is pre-charged to 2.8.

 

[ShaunCorbs]

On a flexi ?

 

[nashant]

On a flexi ?

Nope, piped. I thought I would test the reducing valve by running the cold on a different tap that comes off the main before the combi, then opening a hot this morning. Still get the noise, didn't make a difference. So it's not the pressure on the main that's causing the problem.

 

[ShaunCorbs]

Any pictures of the unvented and pipework ?

 

[nashant]

Is it fine to have separate components instead of a combo valve? If yes, can I confirm with you the order the engineer should be installing them? I know, I shouldn't need to, I should just let them deal with it. But my experience so far has been less than stellar, so would like to be able to verify what they've done.

So should be main -> pressure reducing valve/filter -> tee off for balanced cold -> check valve -> pressure relief valve -> tee off for EV -> into cylinder. That right?

Pics attached

 

[nashant]

And another piece of data. This morning I turned the main completely off before opening the hot tap. The noise started the same, but was more protracted towards the end and sounded kind of like if you were to twang a big spring.

 

[Trynaplumb]

Issue with the expansion. Pretty certain. Have your engineer, check and recharge or replace

 

[nashant]

Charge is fine, was 3 bar (incorrectly left by installing engineers), has now been set to 2.8 in accordance with manufacturer's instructions. What makes you say EV? Some people saying EV, some people saying definitely not EV. Would love to know what the reasoning behind each answer is. Would whatever issue you suspect the EV has cause a couple of seconds of what sounds like a spring twanging?

Having a read about check valve chatter it seems that turbulence can be a cause, and elbows close to the valve can cause that. Looking at combo valve design and the 4th picture I posted, is it possible that the increased pressure/flow from the EV emptying is causing turbulence in the combo where the check valve is located and causing that to chatter?

 

[nashant]

@ShaunCorbs I've found another thread (noisy non return valve. - https://www.plumbersforums.net/threads/noisy-non-return-valve.87559/) talking about a noisy spring check valve and suggesting a swing valve. Would that be suitable in this situation?

 

[nashant]

I should also add that the pressure gauges fitted to the main swing wildly when the noise is happening

 

[SimonG]

I don't like the ev connected to the combi valve. Prefer to t it in closer to the cold cylinder inlet.

 

[nashant]

I don't like the ev connected to the combi valve. Prefer to t it in closer to the cold cylinder inlet.

That sounds like it might solve the issue if it's chatter caused by turbulence in the valve from increased pressure from the EV emptying. Assume that asking the engineer to cap off the EV outlet on the combi valve, swap the elbow to the cylinder for a tee and take that to the EV would be suitable?

I would like to reiterate that I am not planning on doing this work myself, I want to be able to claim on my house insurance should anything go pop. And for the sake of a few quid that's not a risk I'm willing to take.

 

[nashant]

And it's fixed! Had someone move the EV from the combi to the cylinder cold feed and the problem is instantly fixed.