andrews BUFFER-GL200-8 Installation And Service Manual page 13

Secondary Circulation
If a secondary circulation system is required it is recommended that it be connected to the
Andrews buffer similar to Figure 9. The secondary return pipe should be in 28mm pipe and
incorporate a check valve to prevent back flow, smaller pipe diameters can be used but may
have a reduced flow. A suitable WRAS approved circulation pump will be required. On large
systems, due to the increase in system water content, it may be necessary to fit additional
expansion volume to the secondary system by fitting an external expansion vessel to the
circuit. This should be done if the capacity of the secondary circuit exceeds 10 litres.
De-stratification kits
The correct size of de-stratification kit must be used with your buffer to ensure the volume
can be circulated in 1 hour. The pump instructions will need to be reviewed for information on
the cor- rect setting. Please follow the installation schematic (Figure 9) for guidance. When
the system circulates it needs to be specified by the installer to ensure water is not drawn off
during the de-stratification process. If a hot water demand is required during this period cold
water may be discharged from the hot outlet. It is recommended that a check valve be
installed before the pump to stop any risk of cold water draw off through the pump when it is
not in use. For guidance on installation please refer to Figure 9.
Unvented systems
If the cylinder is being used for storage of domestic hot water on an unvented system
additional Temperature and Pressure valve must be fitted to the cylinder hot outlet
connection with the use of a T-piece and ensuring the probe from the Temperature and
Pressure valve is fully immersed in water in the top of the cylinder.
Pipe capacities (copper)
22mm o/d = 0.38 litres per metre run (10 litres =
26m) 28mm o/d = 0.55 litres per metre run (10
litres = 18m) 35mm o/d = 0.83 litres per metre run
(10 litres = 12m) 42mm o/d = 1.23 litres per meter
run (10 litres = 8m)
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