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Page 16
1.0 DESIGN
1.3 SYSTEM DETAILS
Expanson vessel requirements
The ElectraMate 2000 Model EM270 is supplied
with a 40 litre expansion vessel and the model
EM170 is supplied with a 25 litre expansion
vessel. Both are supplied pre-charged to 1.0
bar to accommodate the expansion of total
water content of the system including thermal
store. The size of the expansion vessel provided
with each model is considered adequate
for a typical installation. However it is the
designers/installers responsibility to check this
and provide an additional expansion vessel
if necessary.
The values presented in the table opposite
are based on a maximum store charge
temperature of 85°C. The expansion vessel
must be suitable to accommodate the change
in volume of the water in the primary system
from 10°C to 110°C as specified in BS 5449 :
1990 clause 16.2.
In nor
mal circumstances an initial system
charge pressure of 1.0 bar is suitable for most
domestic installations.
The minimum system pressure (when cold)
should not be less than the static head plus
0.5 bar i.e. the height of the highest point in
the system above the expansion vessel plus a
safety margin of 0.5 bar. If a different system
pressure is required than 1.0 bar the initial
vessel charge pressure must be adjusted to
the same value.
If an additional expansion vessel is required,
this must comply with BS 4814 and must be
suitable for heating circuit temperatures up
to 110°C.
The expansion vessel’s must be sized to
accommodate the expansion of the total
water content of the system i.e. heating circuit
plus ElectraMate 2000 unit. Total expansion
vessel volume required for different operating
pressures and radiator circuit volumes is shown
in the table opposite. The sizing procedure is
outlined in BS 5449 : 1990.
Note : There must be no isolating valve
between the expansion vessel(s) and the
appliance or any other such device.
Expansion vessel volume required for different operating conditions
Safety valve setting (bar)
Vessel charge pressure (bar)
Initial system pressure (bar)
3.0
0.5 1.0
0.5 1.0 1.0
Radiator circuit
v
olumes (litres)
Total system
volume (litres)
Expansion vessel volume (litres)
15 285/185 23.7 39.9 31.1
20 290/190 24.2 40.6 31.6
25 295/195 24.6 41.3 32.2
30 300/200 25.0 42.0 32.7
35 305/205 25.4 42.7 33.2
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