Sat, 30 May 2026 20:14:55 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274635#Comment_274635 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274635#Comment_274635 Fri, 19 Jul 2019 10:00:29 +0100 revor
Being at odds with my understanding of this I queried it and was assured that the instruction was correct and there is even a installation video confirming this. I have trawled through illustrations of systems on the WWW and all examples I can find the vessel is orientated with fluid side up gas side down. I recently bought the very excellent handbook The Solar Heating Design & Installation Guide from CIBSE and it quite clearly states that the orientation of the vessel is fluid side up gas side down.

Any views?

(As an aside with no liquid in the system the solar collector temperature got up to 155 deg C I knew it would get hot but not that hot)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274636#Comment_274636 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274636#Comment_274636 Fri, 19 Jul 2019 10:25:44 +0100 Peter_in_Hungary
I have 5 such pressure vessels, 3 with the fluid coming in at the bottom and 2 with the fluid coming in at the top. (FYI 1 vessel on a DHW system the other providing pressure for cold water from wells). Commercial pressure vessels here have the fluid entering at the bottom with an air valve at the top for topping up/adjusting the pressure probably for ease of access to the valve, however you can also get pressure vessels that are mounted horizontally where the fluid enters at one end and the air valve is at the other, both in the middle of the tank.

If you get a failure of the membrane with the fluid entering the bottom the gas will slowly be absorbed until there is none left and with the fluid at the top then gas will enter the system - and then get absorbed.

Bottom line -I don't think it matters, they work in any orientation (if they have a membrane)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274640#Comment_274640 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274640#Comment_274640 Fri, 19 Jul 2019 11:04:06 +0100 revor Your mention of them being mounted horizontally reminds me of having such a vessel on an irrigation pump fitted with on off pressure switch which I have for watering our vegetables on our smallholding.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274645#Comment_274645 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274645#Comment_274645 Fri, 19 Jul 2019 13:15:02 +0100 Peter_in_Hungary Posted By: revorThank you GR8.
GR8 ??]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274652#Comment_274652 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274652#Comment_274652 Fri, 19 Jul 2019 16:29:35 +0100 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274657#Comment_274657 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274657#Comment_274657 Fri, 19 Jul 2019 17:37:43 +0100 djh https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274664#Comment_274664 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274664#Comment_274664 Fri, 19 Jul 2019 18:28:23 +0100 CWatters
On sealed systems I believe it should enter from the top. Elsewhere it says this is to minimise heat loss from the uninsulated expansion vessel. eg having a hot pipe above a colder uninsulated expansion vessel minimises convection. For same reason it should be on the colder return to the solar panels not the hotter flow.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274665#Comment_274665 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274665#Comment_274665 Fri, 19 Jul 2019 18:34:06 +0100 CWatters Posted By: djhIn a solar system I believe it is sensible to have the expansion tank at the bottom of a descending spur with the connection at the top, so that very hot liquid doesn't get to the membrane in the event of stagnation.

Google found a comment to that effect..

"Continuous temperatures are in excess of rated values for some system components e.g. Circulation Pump and the membrane of the Expansion Vessel"

Not sure if this link will work..

http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&cad=rja&uact=8&ved=2ahUKEwjFi4etvcHjAhXHa8AKHX8iAm0QFjAFegQIAhAC&url=http%3A%2F%2Fwww.barillasolar.co.uk%2Fassets%2Fdownload%2Findex%2Fassets%2F28%2F&usg=AOvVaw1GP5lno-WSZA4WFmiOxdZl]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274671#Comment_274671 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274671#Comment_274671 Fri, 19 Jul 2019 22:31:28 +0100 philedge
Unfortunately having residual air in the system isnt good from a corrosion point of veiw, nor from a pump cavitation point of veiw, nor from a heat transfer point of veiw, so mount the accumulator with the inlet uppermost on the return leg from the tank to the collector to keep the temp low and allow the air to be vented.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274700#Comment_274700 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16180&Focus=274700#Comment_274700 Sun, 21 Jul 2019 12:41:15 +0100 revor