Unvented Heating System - Noise Issue - Gledhill - 6 months on

[jklondon]

Hi, hoping the wisdom of the crowd can provide some steer on what is a highly frustrating noise issue in our system going on for 6 months. After giving up with Dynorod (have homecare) I now have a someone qualified looking at it but the issue persists after numerous works.

Essentially in the morning or late afternoon when we open hot tap (any one) there is a foghorn sound.

The list of what has been done by the new engineer is below*

I have uploaded video here (15 seconds in)

Based in NW London if there is anyone local who can come over and provide another opinion (will pay for your time of course).

Thanks in advance!

*
Visit 4

We attended the above property to install a pressure reducing valve where the cold mains comes into the property. We have also installed a non return valve on the hot water pipework under the kitchen sink. This should stop the mains cold water pressure building up and getting into the hot side causing the noise.

Visit 3

We spoke with the cylinder manufacture Gledhill to see what they now suggest as the noise has returned. They asked if we have carried out the following works all which we have done already (replacement of combination valve, install shock arrestor, check expansion vessel).

They recommend the next step to take is to install a pressure reducing valve by the internal stop cock or a non return valve under the kitchen sink on the hot pipe. By doing this would mean that all the taps are under the same pressure. They feel as the kitchen tap does not go through the combination valve in the loft this can be building up more pressure from the street when none of the taps are in use and back feeding down the hot pipe for the kitchen tap and then back up to the loft.

Visit 2

We attended the above property to replace the combination valve and to install a shock arrestor on the incoming mains. We have also re-positioned the pressure gauge for the system. This should hopefully stop any noises coming from the loft area when you open a tap. We checked the external expansion vessel and this seemed to have charged so this is all o.k.

Visit 1

We attended the above property to investigate an issue with a noise when the hot water tap was on. We managed to hear this sound whilst on site.
We drained away the water from the expansion vessel and checked its pre charge. This was at 2.45 bar and the vessel requires 3 bar.
We topped this up on our pump to 3 bar and left this for 35 minutes. Whilst we had this set we also installed a pressure gauge on the combination valve.
We then removed the pump from the expansion vessel as the pressure held. We then turned the water back on and noticed that the pressure gauge was reading the right pressure passing through the combination valve.

 

[Johntheo5]

Is this a Gledhill Lite?
The pressure gauge is on the incoming mains?, the noise coincides with the pressure drop, what are the these pressures as I can't read them off the gauge.
What is the HW cylinder volume?.
What is the EV volume?.

 

[picasso]

I think I would start by putting the expansion vessel vertical.

 

[jklondon]

Is this a Gledhill Lite?
The pressure gauge is on the incoming mains?, the noise coincides with the pressure drop, what are the these pressures as I can't read them off the gauge.
What is the HW cylinder volume?.
What is the EV volume?.

Hi,

Yes Stainless Lite
Pressure mains = 2.5
Pressure upstairs = 2.3
HW volume = 210 Litres
EV volume = 18 L

Pics attached for HW and EV and system.

Some more info: We had a new bathroom put in and main one redone, it started about a month or so after that - although - noise comes if we open hot water from upstairs bathroom which was untouched in the works.

 

[Johntheo5]

Post #3 video shows the pressure falling from 3.0bar to 1.0bar (noisy operation), this PG looks as if its on the mains supply, you also show a pressure gauge on the PRV outlet (photo 5) reading 3.0bar. When the mains PG is reading 1.0bar does the PRV outlet pressure also fall to 1.0bar which it should?.
If the whole 210L is reheated from cold then the cylinder pressure should then rise to a max of 3.9bar.

If, in fact the mains pressure is falling to 1.0bar with HW demand then the PRV should be set to 1.0bar and the EV pre pressure should be set slightly lower to 0.8bar, this will result in a cylinder pressure of 1.53 bar when its full volume is reheated.

Of course, it should be investigated as to why (IF) the mains pressure falls to 1.0bar, one might expect this to be ~ 5bar with no HW demand.
Is there a balanced cold taken off after the PRV?.

Where is the EV connected to the system?.

 

[SpecialK]

Have you cleaned the filter in the combination valve - Although you do mention its new? I wonder if the water mains cant keep up with the draw hence the pressure drop. Did your new pressure reduction valve on the main incoming come with a pressure gauge?

 

[roguetrader]

Has the vessel been changed?
Had them in the past where the bag inside rubs against the metal casing making similar noises.

 

[Madrab]

Need to be in the vicinity and identify what is actually making the noise, 3 possible areas, the pipework, the combi valve or the EV. Pipework is well clipped so shouldn't be that, combi valve changed so shouldn't be that and it does sound like it a typical EV issue that's causing it.

As mentioned I think the dynamic pressure drop, being so significant - dropping to 1 bar - would be one reason the EV is creating noises, in effect the EV's quick release of pressure, from > 3bar, when the cylinder is fully up to temp, is then causing the membrane to create a noise like that.

As suggested, investigation into the cause of the large swing in dynamic pressure would be advised and I must be honest the guys you've had in up till now don't seem to be very well versed in diagnostics for unvented systems. Throwing parts at it hoping one of them fixes the issue is an expensive way to correct faults.
If that is a true representation of the mains' dynamic pressure then again, as suggested, the PRV and EV would need to be adjusted to suit. The other point would be that if the dynamic pressure swing is so significant why did the installer recommended this system.

What happens to the pressure when multiple outlets are open - H&C?

Where is the EV connected to the system?.

Looks like it may be taken off the side of the combination valve?

 

[jklondon]

Thanks for comments so far. So did another test and taken this video. You can hear the initial noise followed by pause then a whine. It seemed to be coming from the EV, I could feel vibrations.

If we let the water run, one tap full pull of hot water the pressure guage upstairs in loft shows 1 bar. The one next to the cold mains shows 2 bars.

The system has been here for 10 years and fine. I do wonder if the works we did that i mentioned, adding new en-sute ,have caused something or something happened with the in-bound pressure based on works done on the street.

 

[Johntheo5]

Both the mains pressure & the PRV pressure are showing almost 2.0bar which is the (now) dynamic pressure, the mains static pressure (now) appears to be 3.0bar. If 2.0bar dynamic is supplying adequate flow(s) then the EV prepressure should be reset to 2.0bar, after a full reheat the cylinder pressure will then be 2.8bar so pressure only has to fall by 0.8bar when HW drawn down instead of a cylinder pressure of 3.9bar (with 3.0bar prepressure) with a 1.9bar drop when HW is drawn off.
Can you also point out where the EV is piped into the system.

Presume the general pipe layout is like below.

 

[Johntheo5]

This is probably why you have "only" 3.0bar static mains as it is after being reduced with this PRV?, except that this PRV just feeds the cold and you have unrestriced mains going to the combination set, but if so then it should be at a higher pressure than 3.0bar static.

Visit 4

We attended the above property to install a pressure reducing valve where the cold mains comes into the property. We have also installed a non return valve on the hot water pipework under the kitchen sink. This should stop the mains cold water pressure building up and getting into the hot side causing the noise.

 

[jklondon]

Both the mains pressure & the PRV pressure are showing almost 2.0bar which is the (now) dynamic pressure, the mains static pressure (now) appears to be 3.0bar. If 2.0bar dynamic is supplying adequate flow(s) then the EV prepressure should be reset to 2.0bar, after a full reheat the cylinder pressure will then be 2.8bar so pressure only has to fall by 0.8bar when HW drawn down instead of a cylinder pressure of 3.9bar (with 3.0bar prepressure) with a 1.9bar drop when HW is drawn off.
Can you also point out where the EV is piped into the system.

Presume the general pipe layout is like below.
View attachment 307730

Hi, Took a video to show the whole system

 

[SpecialK]

I'm not a plumber but should there be a lever ball valve between the PRV (including pressure vessel) and the unvented tank? The red handled one under the pressure vessel?

Which side is the pressure gauge on? Incoming water pressure or after the reduction valve? Im sure my combination valve is the other way around?

 

[Johntheo5]

Its certainly confusing.

This one shows the PG on the cold mains, then the flow through the combination set, PRV+NRV with the EV connection after the NRV which is correct, then the shock arrestor then a red lever valve (not normally) before the HW cylinder. There is also a balanced cold coming off the bottom of (after) the PRV with a blue isolating Lever valve.

This one is a different PRV but dont know what its feeding?. Is it the 3bar one on the incoming mains?.

 

[SpecialK]

Little more clear from the photo. I'm sure the red lever valve should not be there as you could shut off the expansion vessel and pressure release valve on the combination valve?. Also if the pressure gauge is dropping as per the video then the mains cant keep up.

The second PRV on the mains incoming should be set above the PRV pressure on the unvented? So maybe 4 bar.

Also it would be interesting to know what pressure the unvented PRV is set at because the pressure gauge is on the wrong side?

Its certainly confusing.

This one shows the PG on the cold mains, then the flow through the combination set, PRV+NRV with the EV connection after the NRV which is correct, then the shock arrestor then a red lever valve (not normally) before the HW cylinder. There is also a balanced cold coming off the bottom of (after) the PRV with a blue isolating Lever valve.




This one is a different PRV but dont know what its feeding?. Is it the 3bar one on the incoming mains?.