Mains pressure HW cylinder

PoP · 2004-02-13T18:34:23+00:00

I came across something in my travels yesterday which surprised me abit, and I wondered if others might be able to satisfy my curiosity?I opened the airing cupboard door, inside was a larger than average HWtank which came up to about my chest (maybe 5ft tall). On the HW tankwas a big notice with words to the effect that the HW was supplied atmains pressure.As it happened I had to shut off the HW supply to work on something inthe bathroom, and sure enough this required the rising main to be shutoff in the kitchen in order to kill the HW supply.My experience is obviously limited in this domain, but I've alwaysbeen used to HW cylinders being fed by gravity from the cold headertank in the loft so it was a bit of a surprise to find one that'sbeing fed directly from the rising main. Usually the rising main goesstraight up to the loft to fill the header tank and pretty mucheverything else (apart from a tap in the kitchen perhaps) is droppedfrom that tank.The usual CH/HW piping with divertor valve was in place to the HWcylinder to indirectly heat the HW thru a coil, so I'm pretty surethis HW cylinder isn't being fed directly from a CH boiler.Is this a usual arrangement which I've managed to miss all theseyears, or did I trip over a house that has had something special doneto it? :)Just very curious about the piping arrangement in this instancebecause it seemed odd - I'm not trying to fix a problem with the HWsupply.PoPSending email to my published email address isn'tguaranteed to reach me.

Feb 13, 2004 22 Replies

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Andy Hall 22 years ago

Practically speaking yes, it can be.

Bureaucratically, probably not. It may invalidate the warranty of the system and installation is a controlled activity of the Building Regulations )I'm not certain about maintenance.

.andy

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Ed Sirett 22 years ago

Essentially the top outlet is a 'dip tube' going down through the top 30% of the cylinder. When the cylinder fills the air remaining in the top pocket becomes the expansion volume, the air is typically squeezed to about 1/4 of its original size (3 bar on guage is 4 bar absolute). I'm not sure but one or more of the makes may include some sort of floating baffle.

In non-Megaflow (and clones) the top outlet is just like on a vented cylinder, a hole in the top.

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IMM 22 years ago

Heat banks are better. water stored at low pressure and high pressure mains hot water. Heat banks also last longer if the inhibitor is changed every 4 years.

Explanation:

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