Specifications
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Expansion vessels
The boiler must be directly connected to the expansion vessel in the system using a pipe
with a diameter no smaller than 18mm. The piping must not be obstructed in any way. The
expansion vessel must be at least 7% of volume of the total heating system. The
expansion vessel should be fitted on the suction side of the pump. The point at which it is
fitted is generally accepted as being the neutral point of the system. An expansion vessel
is divided into two compartments and separated by a flexible diaphragm. The sealed side
is charged with nitrogen gas. The open side is connected to the system.
Sizing of an expansion vessel:
Sizing of an expansion vessel is very important as the expansion vessel must be large
enough to accommodate all the expansion of the water.
D The volume of water contained within the system. Manufacturers supply data which
includes water capabilities of such things as boilers and heat emitters.
D Initial pressure of system, or pre-pressurisation, calculated from the static height
which is the vertical distance from the expansion vessel to the highest point.
D The boiler flow temperature. Should the volume fall between two sizes, the larger
size must be used. The volume of the expansion vessel in litres fitted to a sealed
system shall not be less than that given by the table below.
MS10-11C Issue 2 16
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1.5
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2
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Expansion Vessel Volume (litres)
Ϯϱ Ϯ͘ϭ ϯ͘ϱ ϲ͘ϱ ϭϯ͘ϳ Ϯ͘ϳ ϰ͘ϳ ϭϬ͘ϯ ϯ͘ϵ ϴ͘ϯ
ϱϬ ϰ͘Ϯ ϳ ϭϮ͘ϵ Ϯϳ͘ϱ ϱ͘ϰ ϵ͘ϱ ϮϬ͘ϲ ϳ͘ϴ ϭϲ͘ϱ
ϳϱ ϲ͘ϯ ϭϬ͘ϱ ϭϵ͘ϰ ϰϭ͘ϯ ϴ͘Ϯ ϭϰ͘Ϯ ϯϬ͘ϵ ϭϭ͘ϳ Ϯϰ͘ϴ
ϭϬϬ ϴ͘ϯ ϭϰ Ϯϱ͘ϵ ϱϱ͘ϭ ϭϬ͘ϵ ϭϵ ϰϭ͘Ϯ ϭϱ͘ϲ ϯϯ͘ϭ
ϭϮϱ
ϭϬ͘ϰ ϭϳ͘ϱ ϯϮ͘ϰ ϲϴ͘ϵ ϭϯ͘ϲ Ϯϯ͘ϳ ϱϭ͘ϱ ϭϵ͘ϱ ϰϭ͘ϯ
ϭϱϬ ϭϮ͘ϱ Ϯϭ ϯϴ͘ϴ ϴϮ͘ϲ ϭϲ͘ϯ Ϯϴ͘ϱ ϲϭ͘ϴ Ϯϯ͘ϰ ϰϵ͘ϲ
ϭϳϱ ϭϰ͘ϲ Ϯϰ͘ϱ ϰϱ͘ϯ ϵϲ͘ϰ ϭϵ͘ϭ ϯϯ͘Ϯ ϳϮ͘ϭ Ϯϳ͘ϯ ϱϳ͘ϵ
ϮϬϬ ϭϲ͘ϳ Ϯϴ ϱϭ͘ϴ ϭϭϬ͘Ϯ Ϯϭ͘ϴ ϯϴ ϴϮ͘ϭ ϯϭ͘Ϯ ϲϲ͘Ϯ
ϮϱϬ ϮϬ͘ϴ ϯϱ ϲϰ͘ϳ ϭϯϳ͘ϳ Ϯϳ͘Ϯ ϰϳ͘ϱ ϭϬϯ ϯϵ ϴϮ͘ϳ
ϯϬϬ Ϯϱ ϰϮ ϳϳ͘ϳ ϭϲϱ͘ϯ ϯϮ͘ϳ ϱϳ ϭϮϯ͘ϲ ϰϲ͘ϴ ϵϵ͘ϯ
ϯϱϬ Ϯϵ͘ϭ ϰϵ ϵϬ͘ϲ ϭϵϮ͘ϴ ϯϴ͘ϭ ϲϲ͘ϱ ϭϰϰ͘Ϯ ϱϰ͘ϲ ϭϭϱ͘ϴ
ϰϬϬ ϯϯ͘ϯ ϱϲ ϭϬϯ͘ϲ ϮϮϬ͘ϰ ϰϯ͘ϲ ϳϲ ϭϲϰ͘ϴ ϲϮ͘ϰ ϭϯϮ͘ϰ
ϰϱϬ ϯϳ͘ϱ ϲϯ ϭϭϲ͘ϱ Ϯϰϳ͘ϵ ϰϵ ϴϱ͘ϱ ϭϴϱ͘ϰ ϳϬ͘Ϯ ϭϰϴ͘ϵ
ϱϬϬ ϰϭ͘ϲ ϳϬ ϭϮϱ͘ϵ Ϯϳϱ͘ϱ ϱϰ͘ϱ ϵϱ ϮϬϲ ϳϴ ϭϲϱ͘ϱ