Size of Elbi pressure vessel required?

[kristy22]

The Elbi pressure vessel installed shows large variations in pressure when it is on and when it is off. Approx .8 bar variation from hot to cold and cold to hot. Is this normal or is the pressure vessel too small for the number of rads? How does one ascertain the size of vessel required? This one is 24 litres.

 

[peteh20]

if the prv isn't blowing off then the vessel is big enough and its normal to have different presures showing on the guage between a system being cold to a system being hot. Its more important to compare the system after a few days and when when the system is cold hope this helps

 

[kristy22]

Hi Pete

Thank you for this reply. Seems then that the vessel is large enough. Would you suggest then that we switch the heating off for a few days? Builder thinks that there is a leak as vessel loses pressure but no visible signs of water. Any suggestions please?? You obviously have experience of these vessels. We appreciate any comments you may make.

 

[peteh20]

if you turn the heating off and it holds presure it would just mean that the leak happens when the system is hot and could be evapourating then you would have no signs of a leak. Best way is to expose all pipework if you have old pipework in concrete floors this is always a favourite for pin holed pipework happy hunting

 

[kristy22]

Thank you Pete. Leak happens when it is cold too. Estimated today that it is at least 1 litre per day!! No sign of water anywhere BUT there is a lot of new plumbing under new tiled floor! What a thought and how to find the leak because cannot just dig up the floor. Know that there are non invasive leak detecting methods. Wonder if there is anything one can buy to do it oneself???

 

[LIFES A GAS]

Let me get this right, you have pressure rise when system hot and you are also losing system pressure when system is hot or cold? Have you checked the expansion vessel air pressure? Is there a leak in the cylinder coil? the 2 problems are probably not connected.
Martin.

 

[kristy22]

Thank you for your reply. Yes, the system is losing pressure when hot and cold. It is estimated that approx 3 pints of water is being lost per day. The pressure vessel air pressure has not been checked. How does one do this please? No sign of where the water is going unless it is under the kitchen floor which has just been tiled and this is new plumbing. Appreciate your comments. Could the air pressure be causing the prob? The water is not coming out of the top of the pressure vessel, that has been checked. This morn pressure was down to 0 bar, vessel was primed with water. As soon as heating was switched on, soon increased by 0.4 bar, is this normal please.

 

[peteh20]

is there any way of isolating the pipes under the new floor and was the pipework tested under the floor

 

[kristy22]

Hi Pete

Thank you for your reply. I very much doubt whether the pipework was tested. Have seen some of the plumbing left in the loft and have confidence in the work. Was just told that they never had leaks, ha ha!! Shall try and find out if there is anyway of isolating the pipework but think it is doubtful. We reckon the system is losing 3 pints per day. Where could it go??? Could soak into the foundations. Sometimes wonder if there could be faulty plumbing and water is running off somewhere. Is that possible?? There is complex plumbing under this new floor and we have pics of it taken during installation. Believe that there are expensive non-invasive methods of detecting leaks.

As soon as the Valiant wall boiler is switched on there is the sound of water running down a waste pipe but we are told this is normal, just the condensation?

Wonder how one would go about isolating the pipework? Why the pipework was put under this tiled floor, one does not know. With the old system it went upwards, not downwards!! Grateful for your thoughts and expertise. Thank you.

 

[peteh20]

has he put the blow off into the waste pipe

 

[kristy22]

Hi Pete

I do not know but shall find out. Would that be a mistake? Could it cause the loss of water? I shall try and find out tomorrow and let you know. There is some awful looking plumbing in the loft. Overflow from vessel runs into cold water tank, that is nice, isn't it!!

I know that they had to drain down the system again as anti-corrosive agent has not yet been added. I am logging off now as have to go out but shall log on tomorrow. Thank you. Kristy22

 

[peteh20]

thinking that if they've done pipework under the floor without testing what othert short-cuts have they done maybe putting the blow off into the waste would explain the noise your hearing if the presure guage drops while you hear this noise. Then it would be a case of the blow off(prv) discharging and dropping the presure let us know

 

[LIFES A GAS]

The air pressure in the expansion vessel is very inportant, thats what make it do it's job (or not), with your system (water) pressure at zero and the PRV open* attach a tyre foot pump to the schroder valveon the expansion vessel and pressurise it to around 1 bar. * Some pressure releif valves (PRV) can be set in the open position by rotating the red top a little, others have to be held open to release the system pressure so you might need some help.
After pumping to vessel to 1 bar, close the PRV and re-pressirise the system to around 1 - 1.2 bars, if every thing is ok there should be very little movement of the pressure as the system goes from cold to hot certainly nothing like the rise you have mentioned in your earlier post, that is why the expansion vessel is fitted.
Re your leak, you didn't say if you have a hot water cylinder fitted or is it a combi type boiler? If you hava a cylinder it can be difficult to tell if the indirect coil which is pressurised is leaking into the DHW which is at a lower pressure s it is fed by the tank in the roof space, you could: mark the water level in the cold water tank in the loft ( do this with a peice of wire hooked over the edge of the tank and cut off so it just touches the water surface, you now mustleave it for 24 hours or so making sure you dont use any hot tap or any other low pressure colds taps that are fed by that tank. Best to do this with the boiler turned off, when you see your system pressure has dropped to zero then check the water level in the tank, if the level has risen (the end of the wire is under water) and you are sure the ball valve is not letting by, I would then say the coil has failed, there are other ways of proving but the the method above works for me. Hope this helps (I know it might be a bit difficult to understand)
Martin

 

[peteh20]

martin do you think they've put the expansion vessel in the loft and put the blow off over the cold storage????????????????????

 

[LIFES A GAS]

It's possible I guess, but thats not how it's supposed to be done,The outlet pipe from the PRV should be taken outside and either doubled back to face the wall or extended down to ground level, which ever way it must be positioned so that any discharge of water or steam from it cannot create a hazard to persons in or around the premises, or cause damage to any electrical components or external wiring, and the point of discharge should be clearly visible.
Martin.

 

[peteh20]

i know its just how she s explained the pipework in the loft and if they've not tested pipework under tiled floors wonder what other short cuts they have done. Replacing the f&e with a sealed system is the loft is the easiest place for this to happen, would guess they've not brought the excisting cylinder upto regs making the coil suspect and hey presto a leak you cant find.

 

[LIFES A GAS]

i know its just how she s explained the pipework in the loft and if they've not tested pipework under tiled floors wonder what other short cuts they have done. Replacing the f&e with a sealed system is the loft is the easiest place for this to happen, would guess they've not brought the excisting cylinder upto regs making the coil suspect and hey presto a leak you cant find.

Thats my thinking as well, sounds like a real cowboy job.
Martin

 

[peteh20]

yehaw, kirsty can you post some pics it would help a lot

 

[kristy22]

Hi there Pete

Thank you very much. What would you like the pics of please and we shall have a go. By the way what does f&e stand for? Boiler is a Valiant echo plus 438, new RM cylinder, 162 litres. Two cold water tanks side by side in the loft. Another prob!! No hot water in basin in loft and yet Monsoon pump etc etc was meant to give us paradise! Noise from pump a nightmare too because it should have been installed on a paving slab and it is right by the airing cupboard door on the first floor.

Look forward to hearing from you. Thank you so much.

Kisty

 

[peteh20]

wow so many problems. pics of boiler, cylinder and airing cupboard, and basin in loft have you had a loft conversion???????????

 

[LIFES A GAS]

If you are sure that the leak is under the floor, why not inject a leak sealer into the system, it's worth a try and much cheaper than lifting the floor.
Martin.