Discuss Hot Water Tank Expansion Vessel Question in the UK Plumbing Forum | Plumbing Advice area at PlumbersForums.net
OkIt's the total capacity of the E.vessel, if you disconne t the water end and pressurise the air end u tail no .ore water then the full capacity f the E.vessel is full of air and vice
Vers, pressurising,e the water end until o Ir
Pressure is the same capacity, the labeled capacity.
press
Cheers. I tend to go by the appliance data on the hot water tank for its EV settingsThe actual volume should be slightly less than the measured capacity of the E.vessel, the EV must then be able to accommodate the expanded volume which is - 1.7 litres in a 100 system volume.
The EV is normally pre pressurised to say 1 bar and you don't have to have the cold filling pressure greaterthan this but you should fill to 1.5 bR S it will then give water reserve of 2 litres cold to make up for any time you losses etc to avold equent top ups
Does it make any difference if the EV is on a hot water tank or a CH system as far as pressure is concerned?The actual volume should be slightly less than the measured capacity of the E.vessel, the EV must then be able to accommodate the expanded volume which is - 1.7 litres in a 100 system volume.
The EV is normally pre pressurised to say 1 bar and you don't have to have the cold filling pressure greaterthan this but you should fill to 1.5 bR S it will then give water reserve of 2 litres cold to make up for any time you losses etc to avold equent top ups
Just got your post, a unvented cylinder is generally intalled with a PRV which can beDoes it make any difference if the EV is on a hot water tank or a CH system as far as pressure is concerned?
I'm reading that it should be set to the same as the supply pressure when cold which is 1 bar in the UK.
Is that for both usage types HW and CH?
They both have the same water supply. The HW has a max temp of 70C and the CH a max temp of 85C.
The EV I have bought has the same spec as the existing one and comes pre-charged to 3 bar as does the original.
The hot water tank itself specifies EV pre-charge of 3 bar too.
So do I install it at 3 bar or 1.5 bar?
I have had a good hunt around the net and it's really not clear at all.
I'm inclined to pre-charge it to 1.5 bar and keep an eye on it. 1.5 bar makes sense.
What do you think?
Cheers
Wouldn't the cold cylinder pressure in the UK be 1 bar? The supply pressure?It is recommended that the pre charge pressure for a unvented HW CyliNDer EV is set 0.2 bar less than the cold cylinder pressure so a 220 litre HW cylinder with cold pressure of 2.5bar and a 18 liter EV will have 3.4 bar hot pressure.
Ignore previous question.It is recommended that the pre charge pressure for a unvented HW CyliNDer EV is set 0.2 bar less than the cold cylinder pressure so a 220 litre HW cylinder with cold pressure of 2.5bar and a 18 liter EV will have 3.4 bar hot pressure.
8Just got your post, a unvented cylinder is generally intalled with a PRV which can be
set to any pressure as long as its approx 0.5 to 1.0 bar lower than the mains pressure so the above still applies, set it to the cold HW Cylinderr pressure minus 0.2bar.
Th UK mains can be anything up to 5 bar but 1bar is only guaranteed AFAIK. if you look at the setting on the PRV then suggest setting the EV pressure slightly below this, IMO all unvented cylinders should have a pressure gauge installed but in any event even if the precharge pressure is set too low it won't cause a problem.Wouldn't the cold cylinder pressure in the UK be 1 bar? The supply pressure?
See previous post. The 1 bar Google search result is b0ll0x.8
Th UK mains can be anything up to 5 bar but 1bar is only guaranteed AFAIK. if you look at the setting on the PRV then suggest setting the EV pressure slightly below this, IMO all unvented cylinders should have a pressure gauge installed but in any event even if the precharge pressure is set too low it won't cause a problem.
As I said have a look at the PRV setting and set to this slightly less.Ignore previous question.
Just been on to United Utilities and they say their supply pressure is between 2.4 and 4 bar.
So I am going to install it at 3 bar in line with the cylinder and EV pre-charge.
I don't know what this Google query is all about.
Thanks again for your input.
View attachment 75092
The cylinder PRV is 6 bar and the EV PRV is 4.5 bar.As I said have a look at the PRV setting and set to this slightly less.
Ah. The one in the combination valve. Got it. There are 3 valves in total then.The PRV I am referring to is the pressure reducing valve, the cylinder PRV is the pressure relief valve (safety valve) the other PRV that you refer to is probably the expansion valve and as its set to 4.5bar it might lift if you set the EV prechargeto 3bar. Have you got a pressure reducing valve installed? and if so check its setting.
I'm not. But the guy who is supervising the job is.Are you g3 registered as your working on an unvented?
I'm not. But the guy who is supervising the job is.
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