9
221051B
9
SECTION
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
Water Systems (Sealed)
2
5812
Expansion Vessel
Sealed Water Systems
The installation must comply with the
appropriate requirements of the current
issue of BS5449 Part 1, BS6798, BS4814
and BS7074 Part 1 and 2.
See the diagrammatic layout.
Safety Valve
A safety valve must be fitted to a sealed
water system.
It shall be preset, non-adjustable with a
lift pressure of 3bar, incorporating seating
of a resilient material, a test device and a
connection for drain.
Where a safety valve is fitted the drain
from it must be routed clear of any
electrical fittings but positioned so that
any discharge can be seen.
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, 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 Section 7.2.
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 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 capacity of the boiler is given in the Data
Table.
