Glow-worm hxi and Gas Valve - Manual (Page 19)

19 0020008153-05
TEMPORARY
CONNECTION
HOSE
UNION
HOSE
UNION
SUPPLY
PIPE
CONTROL
VALVE
CONTROL
VALVE
DOUBLE
CHECK
VALVE
HEATING
CIRCUIT
DRAIN
POINT
SUPPLY
PIPE
AIR GAP
TUNDISH
CONTROL
VALVE
CONTROL
VALVE
TYPE CA BACKFLOW
PREVENTION DEVICE
BOILER
RETURN FLOW
BOILER
RETURN FLOW
HEATING
CIRCUIT
DRAIN
POINT
Method 1
Method 2
4 Water System
4.11 Sealed water Systems
The installation must comply with the appropriate requirements
of the current issue of BS4814, BS5449, BS6759, BS6798 and
BS7074 Part 1 and 2.
See diagram 4.3 for a suggested layout.
4.12 Safety Valve
A safety valve must be fitted to a sealed system.
It shall be preset, non-adjustable with a lift pressure of 3 bar,
incorporating seating of a resilient material, a test device and a
connection for drain.
The drain from the safety valve must be routed outside the
building, must not discharge above an entrance or window or
any type of public access area, be clear of any electrical fittings
and positioned so that any discharge can be seen.
4.13 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 4.3 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 size is given in the
current issue of BS5449 and BS7074 Part 1.
Example: For an initial design pressure of 0.7 bar, the minimum
total vessel volume required is 0.063 x Total 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, for IE refer to the current edition of
I.S.813 "Domestic Gas Installations".
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.
4.14 Pressure Gauge
A pressure gauge with a set pointer and covering at least 0 to
4 bar (0 to 60 lb/in
2 ) shall be fitted permanently to the system in
a position where it can be seen when filling the system.
4.15 Domestic Hot Water Cylinder
SINGLE FEED INDIRECT CYLINDERS ARE NOT SUITABLE
The domestic hot water cylinder must be of the double feed fully
indirect coil type. It must be suitable for working at a gauge
pressure of 0.35 bar above the safety valve setting.
4.16 Water Makeup
Provision should be made for replacing water loss from the
system using a make up bottle mounted in a position higher than
the top point of the system, connected through a non-return
valve to the return side of either the heating circuit or the hot
water cylinder.
Alternatively, provision for make up can be made using a filling
loop.
Diagram 4.4
11680
4.17 Filling a Sealed Water System
Provision for filling the system at low level must be made, see
diagram 4.4. There must be no permanent connection to the
mains water supply, even through a non-return valve.
We do not recommend filling using artificially softened water.