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221834B
Diagram 2.3
Diagram 2.4
FEED AND
EXPANSION
CISTERN
CYLINDER
FLOW
RET.
FLOW
150 mm
MAX
BOILER
RET.
PUMP
450mm
MIN.
HEIGHT
1150mm
MIN.
22mm (MIN) VENT
15mm (MINIMUM)
COLD FEED
Open (vented) system.
Recommended
relationship between
pump, cold feed and
vent.
15mm (MINIMUM)
BY-PASS WITH
LOCKSHIELD VALVE
HEATING
4357A
2 Water System
2.10 Safety Valve
A safety valve must be fitted to a sealed system.
It shall be preset, nonadjustable with a lift pressure of 3bar,
incorporating seating of a resilient material, a test device and a
connection for drain.
The drain from the safety valve must be routed clear of any
electrical fittings and positioned so that any discharge can be
seen.
2.11 Expansion Vessel
A diaphragm type expansion vessel, conforming to the current
issue of BS4814 (see also BS7074 Part 1 and 2) must be
connected at a point close to the inlet side of the circulating
pump, see the diagrammatic layout, diagram 2.4 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 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.
Note: A higher initial design pressure requires a larger volume
expansion vessel.
Guidance on vessel sizing is also given in the current issue of
BS5449 and BS7074 Part 1.
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 content of the boiler is given in the Data Table 1.
5609
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
40/50-15mm (min)
60-15mm (min)
BY-PASS WITH
LOCKSHIELD
VALVE
RETURN
15mm (min)