Expansion vessel

[b21playa]

Hi

Is there a particular one to use on the cold water side or are they all the same. Also does the size matter

Reason is the 35litre one I have (for 300 litre tank) is damaged and need to either buy another or a neighbour has a new 24litre that I can have if it is suitable.

Thanks

 

[b21playa]

Ignore above, just read it should be at least 10% of capacity rounded up so 35L it is

 

[Johntheo5]

A 300L cylinder + a 35L EV heated to 65C with pre fill pressure of 2.8bar (assuming 3.0bar PRV) will give a final pressure of 3.79 bar.
A 300L cylinder + a 24L EV heated to 65C with pre fill pressure of 2.8bar (assuming 3.0bar PRV) will give a final pressure of 4.27 bar.

Depending on the cylinder design, if the expansion valve installed is 6bar with a cylinder TPRV of 7bar/95C. then a 24L EV can be quite adequate

 

[kidgreen61]

Yes, potable water EVs are different to CH system EVs in that the water doesn't come into contact with the walls of the vessel, if you use a CH vessel you'll end up with brown bath water.

 

[Johntheo5]

I have seen this mentioned before, my only experience is with the "red" ones for CH systems, the largest was 24L but all of them had a bladder installed originally through the neck at the water end with a flange then bolted on, so this water was also never in contact with the walls of the vessel, the air was in contact with the vessel walls at the other end. I have often seen pictures of larger (white??) EVs where the diaphragm is clamped in the middle of the EVs so presumably the water is in contact with the vessel walls but maybe these are corrosion treated for potable water.