Advice - Gledhill Stainless Lite

[townfanjon]

Yes its correct, personally I like them in the correct port on the ICS , but teed in there is fine .
Excessive cylinder temps wont help , is the cylinder stat set at 55/60 degrees?
What is the ex vessel pressure, did the engineer actually check it ?
Have you any idea on the incoming mains pressure is ?

 

[IDC]

Yes its correct, personally I like them in the correct port on the ICS , but teed in there is fine .
Excessive cylinder temps wont help , is the cylinder stat set at 55/60 degrees?
What is the ex vessel pressure, did the engineer actually check it ?
Have you any idea on the incoming mains pressure is ?

Cylinder temp is set around 50 . Had previously tried dropping the temp right down over the course of a few days to see if it made a difference, but it did not.

Not too sure on the incoming pressure as no pressure gauge anywhere in the system.

I don't believe the engineer checked the pressure in the expansion vessel, but, it was a new vessel less than 2 months ago. I guess I can just get a schrader-based pressure guage and attached it to the port to verify?

 

[Brambles]

Possibly worth having having a pressure gauge fitted on your incoming mains and also on the tank inlet after the combination valve.

It may seem to be a bit of overkill, but it makes it so much easier to work out what is going on.

I assume that (in the absence of a balance cold) you have checked all/any mixer taps / valves for high pressure cold back feeding the system?

 

[IDC]

Possibly worth having having a pressure gauge fitted on your incoming mains and also on the tank inlet after the combination valve.

It may seem to be a bit of overkill, but it makes it so much easier to work out what is going on.

I assume that (in the absence of a balance cold) you have checked all/any mixer taps / valves for high pressure cold back feeding the system?

Ok sure, I'll look into getting that done. Hopefully space isnt at too much of a premium after the combination valve (as you can see from the above, it's pretty tight!)

What would be the best way to check for the cold feeding back? I assume turn off each tap/mixer over the course of a few days to try and see if turning one off stops the issue? If identified as the problem, is the fix to have a non-return valves fitted?

 

[Brambles]

IDC,

Ideally work logically through the system to eliminate all the potential causes. The starting point is the incoming mains static pressure. If that is around 4 bar there is unlikely to be an issue for back feeding, but if it is above 6 bar - it could be an issue. Look at all the potential feed in points ( the kitchen mixer is often suspect No 1). Easiest way to test is isolating the mixer on the cold feed and see how the system performs or look for passing through the valves - but that can be difficult to spot sometimes. If that tap is an occasional source of water hammer that too can be an indicator it is passing. If a mixer is suspect I would replace it with a quality brand and not mess around with nrv’s. In my experience shower valves are the least likely suspect (but not always). Better still, if possible, convert to a balanced cold supply

A good G3 engineer who logically works through the system really should be able to solve this for you in a couple of hours. The problem is that some just jump to conclusions, then embark on the systematic replacement of all the the parts until it works or you run out of money!

I probably should not say this, but the G3 course / qualification is just one day ( training and exam). It focuses on the safe installation and operation of pressurised systems. Whilst the basic principles of the system are covered, very little, if any, training is given on fault finding or optimising the operation of the system.

Final points, never assume that the problem is just one issue and don’t tinker with the installation after the combination valve.

Hope this helps

 

[IDC]

IDC,

Ideally work logically through the system to eliminate all the potential causes. The starting point is the incoming mains static pressure. If that is around 4 bar there is unlikely to be an issue for back feeding, but if it is above 6 bar - it could be an issue. Look at all the potential feed in points ( the kitchen mixer is often suspect No 1). Easiest way to test is isolating the mixer on the cold feed and see how the system performs or look for passing through the valves - but that can be difficult to spot sometimes. If that tap is an occasional source of water hammer that too can be an indicator it is passing. If a mixer is suspect I would replace it with a quality brand and not mess around with nrv’s. In my experience shower valves are the least likely suspect (but not always). Better still, if possible, convert to a balanced cold supply

A good G3 engineer who logically works through the system really should be able to solve this for you in a couple of hours. The problem is that some just jump to conclusions, then embark on the systematic replacement of all the the parts until it works or you run out of money!

I probably should not say this, but the G3 course / qualification is just one day ( training and exam). It focuses on the safe installation and operation of pressurised systems. Whilst the basic principles of the system are covered, very little, if any, training is given on fault finding or optimising the operation of the system.

Final points, never assume that the problem is just one issue and don’t tinker with the installation after the combination valve.

Hope this helps

Thanks for the advice. It has been very frustrating so far as, like you've alluded to, I've had expansion vessel and combination valve replace so far, and now suggestion of larger expansion vessel (all from different people), but no checks on if the expansion vessel is correctly pressured, or, as you say, if there is feedback from one of the outlets.

I don't suppose there is anyone here who covers Surrey area on this forum who might be able to offer a thorough troubleshooting/solution?

 

[Chuck]

I don't believe the engineer checked the pressure in the expansion vessel, but, it was a new vessel less than 2 months ago. I guess I can just get a schrader-based pressure guage and attached it to the port to verify?

Someone else may have made the point already (sorry, haven't time to read the whole thread in detail right now) but I think it is worth emphasising.

To work correctly the expansion vessel has to contain the correct total amount (moles) of gas, usually air. One explanation for the symptoms the OP described is a pressure vessel that is undercharged. The manufacturer's instructions are a choreographed routine for getting the right amount of air in and need to be followed carefully. Just pumping/bleeding air in/out to achieve a target pressure without knowing the state of the system isn't enough because it doesn't tell you the total volume of air that ends up in the EV.

 

[IDC]

Someone else may have made the point already (sorry, haven't time to read the whole thread in detail right now) but I think it is worth emphasising.

To work correctly the expansion vessel has to contain the correct total amount (moles) of gas, usually air. One explanation for the symptoms the OP described is a pressure vessel that is undercharged. The manufacturer's instructions are a choreographed routine for getting the right amount of air in and need to be followed carefully. Just pumping/bleeing air in/out to achieve a target pressure without knowing the state of the system isn't enough because it doesn't tell you the total volume of air that ends up in the EV.

Ok thanks, sounds like starting with the EV pressure is the best bet. What should I expect an engineer to do to ascertain what the pressure in the vessel should be?

 

[Chuck]

What should I expect an engineer to do to ascertain what the pressure in the vessel should be?

They should consult (or know by heart) the instructions provided by the manufacturer. The procedure is typically to close the CW inlet, reduce the pressure in the DHW to 0bar (gauge), pre-charge the EV to whatever pressure is to be used for the DHW, say 3bar. Open the CW inlet and the DHW will come up to 3bar. This loads the maximum amount of gas into the EV, which will minimise the pressure rise when the water in the system expands due to heating. I say 'gas' rather than 'air' as nitrogen is sometimes used instead.

A competent plumber with a G3 ticket won't need any supervision to get this right and will happily explain what they are doing and why if you show a polite interest.