9
221460C
3 Water Systems
3.6 Expansion Vessel
A diaphragm type expansion vessel, conforming to the current
issue of BS4814 (see also the current issue of BS7074 Part 1
and 2) must be connected at a point close to the inlet side of the
circulating pump, see diagram 3.3, unless laid down differently
by the manufacturer.
The expansion vessel volume depends on the total water
system volume and the initial system design pressure. For any
system an accurate calculation of vessel volume size is given
in the current issue of BS7074 Part 1.
Example: For an initial system design pressure of 0.7bar the
minimum total vessel volume required is 0.063xTotal System
volume.
Guidance is also given in the current issue of BS5449.
The charge pressure must not be less than the static head of the
system, that is, the height of the highest point of the system
above the expansion vessel.
The water capacity of the boiler is given in Section 1.
3.7 Pressure Gauge
A pressure gauge with a set pointer and covering at least the
range of 0 to 4 bar (0 to 60lb/in
2
) shall be permanently fitted to
the system in a position where it can be seen when filling the
system.
3 LITRES (0.66 gals)
MAKE-UP BOTTLE
(if required)
NON-RETURN
VALVE
AUTO
AIR
VENT
FLOW
DRAIN
COCK
BOILER
SAFETY
VALVE
(Make-up
alternatives)
EXPANSION
VESSEL
PRESSURE
GAUGE
CIRCULATING
PUMP
FILLING POINT
AIR
RELEASE
POINT
HEATING
CIRCUIT
15mm (min)
BY-PASS WITH
LOCKSHIELD
VALVE
RETURN
SEALED WATER SYSTEM DIAGRAMMATIC LAYOUT
EXPANSION VESSEL SYSTEM
EXPANSION VESSEL
PRESSURE (BAR)
A = SYSTEM VOLUME
Diagram 3.4
INTIAL SYSTEM
PRESSURE (BAR)
EXPANSION VESSEL
VOLUME (LITRES)
INTIAL SYSTEM
PRESSURE (BAR)
EXPANSION VESSEL
VOLUME (LITRES)
EXPANSION VESSEL
PRESSURE (BAR)
0.5
1.0
A X 0.075
A X 0.126
A X 0.098
A X 0.171
0.5
1.0
1.0
1.5
Diagram 3.3
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