Unvented system - Very loud vibration when drawing hot water.

[GeddyMortgage]

Hi all,

Moved into a property earlier this year and noticed a really strong vibrating sound coming from the cylinder room on the top floor.

It happens for maybe 4-5 seconds in the morning when we're drawing hot water for the first time. Usually notice it when one of us has a shower in the morning but it can occur when we draw hot water for the first time in the day from any tap in the house too.

Literally as soon as the water starts feeling hot from the shower/taps that first time in the morning, you get this incredibly loud vibration in the cylinder room. It sort of dies down after that and won't do it really for the rest of the day. Never does it when drawing cold water either.... and probably worth mentioning in the past when we've been away for a few days and drawn hot water for the first time when back, it's an even an even stronger vibration then.

It's a tight space to try and show the setup of the boiler room. So i've done a couple videos too. Linked below separately.

Boiler Video 1

Boiler Video 2

Lastly i have had British gas out a couple times, I believe they replaced the white EV once or twice already...and said if the problem persisted they wouldn't know what else to do. Hence posting here, so really any guidance or things we can try would be massively appreciated as the noise is becoming a course for concern now.

thanks very much

G

 

[Mottie]

I had a similar noise on mine but it only continued for about 5 seconds after turning off the shower. It turned out to be coming from the combined pressure reducing/pressure relief valve thingy. It cured itself after about a week and has never come back.

 

[Madrab]

Cant see the video as it's not rated without logging in.

These types of droning from an unvented cylinder (UV) are usually either the PRV in the control group or it's an expansion vessel issue. Get the UV serviced

 

[Johntheo5]

Hi all,

Moved into a property earlier this year and noticed a really strong vibrating sound coming from the cylinder room on the top floor.

It happens for maybe 4-5 seconds in the morning when we're drawing hot water for the first time. Usually notice it when one of us has a shower in the morning but it can occur when we draw hot water for the first time in the day from any tap in the house too.

Literally as soon as the water starts feeling hot from the shower/taps that first time in the morning, you get this incredibly loud vibration in the cylinder room. It sort of dies down after that and won't do it really for the rest of the day. Never does it when drawing cold water either.... and probably worth mentioning in the past when we've been away for a few days and drawn hot water for the first time when back, it's an even an even stronger vibration then.

It's a tight space to try and show the setup of the boiler room. So i've done a couple videos too. Linked below separately.

Boiler Video 1

Boiler Video 2

Lastly i have had British gas out a couple times, I believe they replaced the white EV once or twice already...and said if the problem persisted they wouldn't know what else to do. Hence posting here, so really any guidance or things we can try would be massively appreciated as the noise is becoming a course for concern now.

thanks very much

G

Don't know what make your cylinder is but there are quite a few very unhappy Gledhill Lite users on various sites, complaining of the same problems, some unresolved, what are the volumes of the cylinder and EV?.

 

[GeddyMortgage]

Cant see the video as it's not rated without logging in.

These types of droning from an unvented cylinder (UV) are usually either the PRV in the control group or it's an expansion vessel issue. Get the UV serviced

Thanks - i didnt realise i had to rate the content in the videos. It's set to all audience now if that helps?
As far as I know the UV hasn't been serviced. We did just have the boiler serviced however.

 

[GeddyMortgage]

Don't know what make your cylinder is but there are quite a few very unhappy Gledhill Lite users on various sites, complaining of the same problems, some unresolved, what are the volumes of the cylinder and EV?.

Brand is Tempest? or Telford?

Images of the specs for the cylinder / ev attached below.

 

[Justin Passing]

Here's a thought - might be wrong but I've known it fix the motorboat in one of my own systems.

You've got a long vertical pipe there, going up to some amount (which depends on the precharge pressure) of water in the EV, with air on the upper side of a rubber diaphragm.
When you open a tap, the air expands like a spring and pushes some water out because the water pressure has dropped.
If there's some air on the underside of the rubber diaphragm, it's another "spring". Wherever you have two springs in opposition with a damping (time delay) you can get a resonance.
If you put your hand on the EV while someone opens a tap you might feel it more than elsewhere.

So you may have air trapped in that lower side. Solution, turn the EV over, and put an air vent on the high point. Can be auto or manual, I'd say auto, though you may find you leave it closed.

Where people find it stops by itself, it could well be that the air got dissolved in the water and circulated, leaving no bubble.. But yours can't get out because it's a long way down. If there's a small but frequent supply of air for any reason, it would accumulate. Suggesting an auto vent.

It also depends what precharge pressure your EV has ( ie when disconnected). Some people use 1 bar, some use 3 (which it says) or more than that. They often come with a very high pressure). Then it depends on the mains and regulator pressure, pipe runs etc , how far the pressure drops when you open a tap, so how much water comes out of the EV. I'll leave you to ponder that, because technically anyone who works on these has to have a G3 qualification.


Also - that pinkish circulator pump should be dead horizontal, because they don't have endthrust bearings. Doesn't appear to be.
Think about insulation too, for both heatloss and frost.

 

[Johntheo5]

Brand is Tempest? or Telford?

Images of the specs for the cylinder / ev attached below.

View attachment 275969View attachment 275970

If 250L of water is heated from 15C to 65C and with a 18L EV (and assuming charging pressure of 3bar) then the final pressure will be 4.36bar and the pressure will fall to 3.0bar once 4.58L of HW is drawn off. Its highly unlikely that you will be reheating this vol of water each night or day so assuming 150L then final pressure will be 3.72bar and pressure will fall to 3.0bar once 2.75L of HW is drawn off. However assuming the 250L ("worst" case) then I would suggest, in the morning, after cylinder reheat, just crack (slightly) open a HW tap to give just a trickle of HW, let this flow into a 5L container/bucket and once 5L in this container, open the hot tap fully or shower or whatever causes the most vibration and see if it re occurs. You can try this during the day as well.

It's also recommended that the (pre) charging pressure is set 0.2/0.5bar lower than the PRV pressure of 3bar as it is suggested that this helps to prevent water hammer or the above?. If set 0.5bar lower It will still only result in a final pressure of 4.64bar in a full 250L reheat.

 

[Madrab]

Get someone to open the hot tap in the morning whilst you hold the control set (see pic below) and see if you can feel it vibrate.

Look for something similar to this on the cold water inlet to the cylinder

 

[Mottie]

Get someone to open the hot tap in the morning whilst you hold the control set (see pic below) and see if you can feel it vibrate.

Look for something similar to this on the cold water inlet to the cylinder

That’s what was vibrating on mine but only after I had switched the hot tap off.

 

[Johntheo5]

I'd like to see what the EV charge pressure is since it stopped as I would certainly get the G3 to set mine to 2.5bar if had a unvented cylinder as the EV diaphragm cannot bottom out each time the expansion volume is then run off.⁹

 

[GeddyMortgage]

That’s what was vibrating on mine but only after I had switched the hot tap off.

I'll have to wait till tomorrow to see if that thing in the image is vibrating. It only did a little vibration this morning as we were using the hot water late last night.

See the attached video anyway of the small vibration, I can't say if this is the only place its vibrating but it does feel like the EV is vibrating atleast.

Boiler Small Vibration

 

[GeddyMortgage]

Get someone to open the hot tap in the morning whilst you hold the control set (see pic below) and see if you can feel it vibrate.

Look for something similar to this on the cold water inlet to the cylinder

I've found one of them yes. I mentioned on a reply above that we're already had the vibration today so won't be able to see if that bit particularly is vibrating. But I've took a photo of its location on the off-chance that'll shed some light on the setup/problem.

See the images below, It looks like it's connected in 4 different ways, the 3 that run back towards the boiler/cylinder i've colour coded on both sides and annotated accordingly, does that generally look correct? or could something wrong in the setup be causing the issue here? As from memory I think BG may have replaced that part already once.

Also apologies in the lack of know how in my replies, i'm not technical but hoping the help on here may narrow things down a bit if I need to get a G3 person out to resolve this if It ends up being something likely beyond my skill level (low, ha)

 

[Johntheo5]

OK, have a look at my (your) edited photo and make a few comments.

 

[GeddyMortgage]

OK, have a look at my (your) edited photo and make a few comments.

Thanks for that, In that order.

Purple :- Does not run to EV, is connected to both T/P and Return on Cylinder.
Green :- Does not run to EV, is connected to both T/P and Return on Cylinder.
Blue :- Does run to EV, EV tees off this before it hits the COLD on Cylinder.

One thing I noticed then when tracking the pipes - Should the Return pipe be hot where it connects to the cylinder? Not the Hot Return, just Return.