'Bang' from Unvented HW tank Expansion Vessel
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Thanks to all for helpful suggestions, been trying to resolve the problem.
Before Christmas Manufacturer said to drop EV to same as incoming, ie 2.2bar per their gauge. Result: the pipe to the EV juddered violently whenever a hot tap was turned on.
I got Water board to visit and check incoming pressure: 2.8bar static, 16ltrs/min flow rate.
The Manfctr said change from gravity to mains in the rest of the house pipework could be the problem. So I allowed the water in the HW tank to cool, Thermostat was calling for heat but it was not applied. The pressure from the HW tank into the household pipework is still at the incoming 2.2 or 2.8bar, whichever gauge you believe. There is no judder in system at all. Thus I can’t see that it’s anything to do with the house pipework.
Before going back to Manufacturer I decided to check things out myself at various EV pressures :
a. 3.4 to 2.4bar - ev pipe judders when HW tap turned on after water heated. It then judders again when the tap is turned off. No judder at other times.
b. 2.2 to 1.8 bar - ev pipe judders whenever a HW tap is turned on.
c. 1.7 bar - there is no judder in normal use either before or after heating but when releasing pressure for maintenance etc, there is a very long flow of water before it stops which is accompanied by a very violent judder of the EV pipe. I don't know that the EV is doing anything at this low pressure and don't think that it would be correct to drop it to this.
Any thoughts?
I am just the ‘man on the Clapham Omnibus’ and therefore do not understand all this but rightly or wrongly I am convincing myself that the problem is the EV itself. It is made by Varem, Italian I think, are there ‘good and poor’ makes of EV?
Before Christmas Manufacturer said to drop EV to same as incoming, ie 2.2bar per their gauge. Result: the pipe to the EV juddered violently whenever a hot tap was turned on.
I got Water board to visit and check incoming pressure: 2.8bar static, 16ltrs/min flow rate.
The Manfctr said change from gravity to mains in the rest of the house pipework could be the problem. So I allowed the water in the HW tank to cool, Thermostat was calling for heat but it was not applied. The pressure from the HW tank into the household pipework is still at the incoming 2.2 or 2.8bar, whichever gauge you believe. There is no judder in system at all. Thus I can’t see that it’s anything to do with the house pipework.
Before going back to Manufacturer I decided to check things out myself at various EV pressures :
a. 3.4 to 2.4bar - ev pipe judders when HW tap turned on after water heated. It then judders again when the tap is turned off. No judder at other times.
b. 2.2 to 1.8 bar - ev pipe judders whenever a HW tap is turned on.
c. 1.7 bar - there is no judder in normal use either before or after heating but when releasing pressure for maintenance etc, there is a very long flow of water before it stops which is accompanied by a very violent judder of the EV pipe. I don't know that the EV is doing anything at this low pressure and don't think that it would be correct to drop it to this.
Any thoughts?
I am just the ‘man on the Clapham Omnibus’ and therefore do not understand all this but rightly or wrongly I am convincing myself that the problem is the EV itself. It is made by Varem, Italian I think, are there ‘good and poor’ makes of EV?
This is the first time I have read this thread!
The EV should be pressurised to same air pressure as the normal working pressure of the cylinder but with the cylinder depressurised!
The EV is just that and it does not need a low resistance pipe into it.
I would be inclined to increase the resistance and see what effect that has on the problem ( holefully to tune it out ).
Tony
The EV should be pressurised to same air pressure as the normal working pressure of the cylinder but with the cylinder depressurised!
The EV is just that and it does not need a low resistance pipe into it.
I would be inclined to increase the resistance and see what effect that has on the problem ( holefully to tune it out ).
Tony
As Mickyg suggested check mains inlet pressure against EV pressure.
Do this at the PRV next to the Tribune - not where the mains enters the house.
Have you got a water softener - you could lose 1 bar through a softener.
This could mean your inlet pressure to the Tribune PRV is around 2bar, or even less if it's fitted in your attic !
In this scenario setting the EV at about 1.7 would be about right.
Do this at the PRV next to the Tribune - not where the mains enters the house.
Have you got a water softener - you could lose 1 bar through a softener.
This could mean your inlet pressure to the Tribune PRV is around 2bar, or even less if it's fitted in your attic !
In this scenario setting the EV at about 1.7 would be about right.
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Agile, Please excuse my layman understanding of this but what do you mean by "does not need a low resistance pipe into it"?
and does "be inclined to increase the resistance " mean increase the pressure in the EV or as 'Wetshoes' suggests decrease it?
and does "be inclined to increase the resistance " mean increase the pressure in the EV or as 'Wetshoes' suggests decrease it?
I explained how to set the air pressure in the first part of my posting.
The second was really mostly intended for the professionals.
Unvented cylinders are covered by special regulations and only those with the qualification should work on them.
So I cannot give you detailed advice as that, if misinterpreted by someone without the relevant background knowledge, could result in a dangerous situation or even cause a large explosion.
Tony
The second was really mostly intended for the professionals.
Unvented cylinders are covered by special regulations and only those with the qualification should work on them.
So I cannot give you detailed advice as that, if misinterpreted by someone without the relevant background knowledge, could result in a dangerous situation or even cause a large explosion.
Tony
Agile, appreciate your comments and reasons but could you please at least answer me this: if the incoming pressure at the PRV is around 2.2bar do you consider that dropping the EV to circa 1.7bar which seems to be the low point at which the juddering disappears, could be ‘dangerous’?
The air pressure ( with cylinder at zero ) should equal the working pressure of the cylinder.
Until you are able to measure this I cannot advise you to make any changes to the air pressure because you dont have the information needed to base a decision on.
All Wetshoes was doing is saying that the cylinder pressure in use could be considerably lower than the set or assumed pressure.
I dont encourage any gas or unvented DIY work by anyone who is not only qualified but also sompetent. Those things dont always go together.
Tony
Until you are able to measure this I cannot advise you to make any changes to the air pressure because you dont have the information needed to base a decision on.
All Wetshoes was doing is saying that the cylinder pressure in use could be considerably lower than the set or assumed pressure.
I dont encourage any gas or unvented DIY work by anyone who is not only qualified but also sompetent. Those things dont always go together.
Tony
Agile, I apologise for persisting with this but I have been trying without success to get this problem sorted by Range and the installer for the last 12 months. I am trying to contact them again, but I need to understand the problem myself first so that I do not get bamboozled by them when I do speak to them so:
There is a pressure gauge fitted to the inlet control set of the HW tank.
The static pressure per that gauge is 2.2bar. ie the incoming supply static pressure.
When water flows from a HW tap the gauge drops, depending on how fully a HW tap is turned on, to a low when the tap is on full of 1.0bar.
Is the working pressure of the Tank therefore 2.2bar or anything down to the 1.0bar?
There is a pressure gauge fitted to the inlet control set of the HW tank.
The static pressure per that gauge is 2.2bar. ie the incoming supply static pressure.
When water flows from a HW tap the gauge drops, depending on how fully a HW tap is turned on, to a low when the tap is on full of 1.0bar.
Is the working pressure of the Tank therefore 2.2bar or anything down to the 1.0bar?
You seem to be saying that the pressure gauge measures your incoming water supply pressure.
The working pressure will always be lower.
You have a higher resistance supply pipe so with your open tap the pressure has already fallen to less than half. But thats at the INLET so its anybodies guess what it falls to at the outlet.
In my view your incoming supply is totally inadequate for proper unvented performanance.
I suppose your installer never measured the supply dynamic flow rate? Little surprise its not working properly.
I realise you would love me to give you detailed instructions. I cannot do that because I dont have all the technical information and I must not be seen to be encouraging unregistered work on unventeds.
Your situation should be seen as further evidence that a competent installer should be chosen who really understands exactly what he is doing.
Tony
The working pressure will always be lower.
You have a higher resistance supply pipe so with your open tap the pressure has already fallen to less than half. But thats at the INLET so its anybodies guess what it falls to at the outlet.
In my view your incoming supply is totally inadequate for proper unvented performanance.
I suppose your installer never measured the supply dynamic flow rate? Little surprise its not working properly.
I realise you would love me to give you detailed instructions. I cannot do that because I dont have all the technical information and I must not be seen to be encouraging unregistered work on unventeds.
Your situation should be seen as further evidence that a competent installer should be chosen who really understands exactly what he is doing.
Tony
Agile, Thanks for your comments, I respect your position and appreciate that you cannot make recommendations re pressurised systems.
Prior to deciding what to install I did ask the Installer whether the supply pressure was adequate. He said that he thought it was and despite the apparent ‘low’ working pressure we do not have any problems with supply at the taps, shower, bath, wash machine etc, albeit not all are on at same time.
It seems to me that the problem results from everyone so far assuming that the working pressure and the supply pressure were about the same at 3 bar.
Because it looks as though the working pressure is below 2bar I have dropped the EV to 1.9bar and so far it seems to have settled down.
I will speak with the manufacturer when the current weather eases and try to arrange for his Engineer to call to check the system over for a final time.
One final question: Precisely how does the EV Bladder and surrounding pressure in the EV tank work? I realise that the EV takes up the expansion from the HW tank, but after the bladder receives the water, is this water ‘pushed’ back from the bladder into the tank when a tap is turned on and the HW tank pressure reduces?
Once again thanks to everyone for the helpful comments (and apologies for long posts).
Prior to deciding what to install I did ask the Installer whether the supply pressure was adequate. He said that he thought it was and despite the apparent ‘low’ working pressure we do not have any problems with supply at the taps, shower, bath, wash machine etc, albeit not all are on at same time.
It seems to me that the problem results from everyone so far assuming that the working pressure and the supply pressure were about the same at 3 bar.
Because it looks as though the working pressure is below 2bar I have dropped the EV to 1.9bar and so far it seems to have settled down.
I will speak with the manufacturer when the current weather eases and try to arrange for his Engineer to call to check the system over for a final time.
One final question: Precisely how does the EV Bladder and surrounding pressure in the EV tank work? I realise that the EV takes up the expansion from the HW tank, but after the bladder receives the water, is this water ‘pushed’ back from the bladder into the tank when a tap is turned on and the HW tank pressure reduces?
Once again thanks to everyone for the helpful comments (and apologies for long posts).
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