Noise from unvented hot water system

[George Isles]

OK, that's a bit of important information .... you are using a pumped accumulator running @ ~ 2bar. Is it an ST?

As a first, the engineer should be looking to align the pre-charge closer to the input pressure to minimise the differential once the cylinder is fully heated. It sounds like there is a 'sweet spot' with the EV where the pressure release through the EV's baffle is causing a resonance, creating the 'fog horn' noises. You did say that a new PRV/Control group was installed? That would generally rule out the PRV. It may also be an idea to calibrated the PRV closer to the Accumulator's output.

I'm afraid to say though, you could really do with an engineer that is experienced with working with these types of systems, especially when yours is a bit of a hybrid, using an accumulator. This is really UV/EV 1'o'1 and he should be running through all of this stuff. That being said, Gledhill should also be asking the right questions and you shouldn't really have to rely on a forum to get to the bottom of it all for you, not that giving you advice is any issue it's just a long drawn out process for you and it shouldn't need to be.

You really need someone that can work through all of this at one visit, rather than having to come back here once something is tried but doesn't work.

Unfortunaely Gledhill dont seem to have an answer, the engineer I am using came on recomendation from Gledhill and has apparetly installed hundreds of similar systems....

The cold water water has a precharge of 4bar but the incoming main has an adjustable monoblock pressure reducing value with up and downstream gauges on.

It's a Stuart Turner Mainsboost system and we have tinkered about with the pressure (from 2.0-3.0bar) but that hasnt really made much difference.

Engineer is coming back in a couple of weeks and is talking about putting a secondary expansion vessell in (not sure where though)

Bit that is most confusing for me is if we drain the system de-pressurise the EV then re-set it all the noise goes away for a few weeks then slowly returns and continues to get worse!

Really appreciate all the comments and help though so at lease I can challenge/make suggestions to the engineer

 

[Johntheo5]

IF the PRV & EV are both presently set to 3.0 bar you might consider (until the engineer returns) setting your pump to say 4 bar, this will ensure that both the PRV & the EV are in step, also, since the noise is apparent while you are running off the expanded volume after heat up, you might/can monitor for any noises between heating cycles while drawing off HW.
You might suggest to your engineer/G3 that he installs a EV isolating/drain valve as it makes life a lot easier and doesn't contravene any safety regulations as the EV can never be considered as part of the overall safety protection as they can and do fail regularly.
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[Madrab]

Unfortunaely Gledhill dont seem to have an answer, the engineer I am using came on recomendation from Gledhill and has apparetly installed hundreds of similar systems.

I must admit that sounds like a bit of a misnomer, I would question as to whether he has installed hundreds of systems specifically on pumped accumulators. Not that it makes much difference anyway, he just needs to keep working through the problem.

The cold water water has a precharge of 4bar but the incoming main has an adjustable monoblock pressure reducing value with up and downstream gauges on.

Sorry, a little confused by that statement, what on the cold has a pre-charge of 4bar ... or was that meant to be 1.4bar?

Engineer is coming back in a couple of weeks and is talking about putting a secondary expansion vessell in (not sure where though)

If that removes the issue then that will prove, IMO, is that there is a problem with the main EV, if he fits hundreds of these systems then no reason he can't get another EV and replace the one you have, if it doesn't sort it he'll have a spare EV for his stock. Wouldn't be the first time a new EV isn't right, out of the box.

Bit that is most confusing for me is if we drain the system de-pressurise the EV then re-set it all the noise goes away for a few weeks then slowly returns and continues to get worse!

Not the first time I've come across that ... and that again points to the EV as it really is the only thing I would think that would change it's behaivour like that.

Has it been established exactly where the noise is coming from? If you place a large screwdriver against certain spots and place the other at your ear you can hear specifically where its loudest. That will prove difinitively what is generating it.

 

[George Isles]

So.....7 months on and 3 weeks ago I finally got the plumber back and he changed the EV, set the precharge to 2.5bar and all was good.....until this morning when the dreaded noise came back!!

Back to the drawing board, any further suggestions as no one, not the plumber, Gledhill or google seem to have any ideas!

Thanks all

George

 

[Madrab]

So the only thing now that hasn't changed it seems is - the pipework.

Without having to read back through everything, I can't remember where on the pipework the EV take off is located? If everything else has been ruled out, I'd now be tempted to look at that.

Very rarely recommend flexi's but thinking it through and scraping the bottom of the barrel, I'd also be tempted to try a high quality S/S flexi to connect to the EV, the flexibility in the pipe may reduce vibration/resonance.

 

[Johntheo5]

So.....7 months on and 3 weeks ago I finally got the plumber back and he changed the EV, set the precharge to 2.5bar and all was good.....until this morning when the dreaded noise came back!!

Back to the drawing board, any further suggestions as no one, not the plumber, Gledhill or google seem to have any ideas!

Thanks all

George

Can you see exactly where the EV outlet pipe is teed into the system, this is very important. (may have asked before).
If its installed in the cold water supply before the combination valve set which has a non return valve incorporated betwwen the PRV & the expansion relief valve then effectively no EV and every time the cylinder reheats then the expansion valve will eject a litre or two of water at 6bar pressure and may cause problems when opening a hot water tap first thing in the morning or after every reheat.

 

[Johntheo5]

Post 12 I think shows it connected in correctly, after the PRC&NRV.

 

[dilalio]

Small EV on the cold inlet?
Megaflo advise this when cold mains is run through a "heated space".
Just a thought.

 

[Johntheo5]

It may, who knows?. the balanced cold mains take off from the PRV isn't utilized either, the cold isn't from the mains but is pumped via a accumulator tank with pump set to various settings with a 0.2bar differential. The vibration only seems to happen "normally"when the hot water is drawn off in the morning for ~ 8 secs or so which would coincide with dropping the pressure due to removing the expanded volume, ~ 4.5L & 1.1bar if whole cylinder reheated and ~ 2.3L & 0.5bar if 1/2 cylinder volume required reheat.

Some people had to get rid of their Gledhill stainless Lite as they never found a solution to their problems.

 

[Agile]

I have often used a long flexible.

Primarily to produce a series resistance in the flow in/out of the EV. Most of them have a quite small internal diameter.

 

[Johntheo5]

To confirm the mainly "morning" problem maybe before night or early morning reheat, just crack open a HW tap to give a trickle, only ~ 3/5 litres has to be drawn off over the reheat period, this will prevent the cylinder rising above the cold pressure overnight then see if problem still there when hot tap/shower fully opened as per normal routine.

 

[dilalio]

Incoming cold main pressure usually also drops during peak periods. This could be coinciding with rising pressure during hot regeneration. Maybe also try changing the reheat schedule to not coincide with peak demand.

 

[powischr]

Hello, I appreciate this forum is a years old but did OP find a solution? We've found ourselves in a similar situation and recently had the EV changed but noise has returned. Please let me know if you found a solution, thanks

 

[George Isles]

Unfortunately no one, including Gledhill, ever solved it….it just stopped and…..touching a lot of wood right now, hasn’t returned but I live in constant worry it will come back as it never got solved

 

[powischr]

Unfortunately no one, including Gledhill, ever solved it….it just stopped and…..touching a lot of wood right now, hasn’t returned but I live in constant worry it will come back as it never got solved

Thank you for your reply! Glad to hear noise has stopped! Fingers crossed it doesn't come back and our noise stops I'll keep this forum updated if we find a solution. Thanks