Expansion Tank
In the mini-chiller unit, the expansion tank is located on the storage tank. However, this tank is
only available in the larger units, i.e. AC 75B, AC 100B, AC 125B.
For the smaller units, i.e. AC 40A, AC 50A and AC 58A, the expansion tank must be located
externally.
Generally, the expansion tank provides a space into which the water can expand or from which it
can contract as the water undergoes volumetric changes with respect to changes in temperature.
Therefore, it is recommended for such an expansion tank to be installed externally for the
smaller mini-chillers when running cooling only cycle, but it is compulsory to do so for the heat
pump units with both cooling and heating cycles. Failure to do so will cause serious damage to
the hydraulic components in the unit and also may cause cracking of the piping network. This is
due to the expansion of the hot water in the pipes.
To allow for this expansion or contraction, the tank provides an interface point between the water
and a compressible gas (e.g. air or nitrogen). There are 3 types of expansion tank available:
a. A closed tank which contains a captured volume of air and water
b. An open tank, i.e. with the water surface open to the atmosphere
c. A diaphragm tank, in which a flexible membrane is inserted between the air the water
The expansion tank which is used in the mini chiller units is of type (c). This type is
recommended as the diaphragm will prevent the air dissolving into the water.
Tank body
Air
Diaphragm
Water
Connecting pipe
The tank is usually installed vertically, either upwards or downwards. However, due to space
considerations, it is also possible to install it horizontally.
Downward installation
Horizontal
installation
Section 6 Page 90
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