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priate to one of these methods. The system pressure must
not be less than the static head of the system.
A
safety valve
set at 3 bar must be fitted to the flow pipe exi-
ting the appliance. It should be as close to the appliance as
practical and there shall be no restrictions between it and the
appliance. It should be connected above or to the side of the
pipe centre line in a position that is accessible for testing. The
outlet from the valve should be routed so that any discharge,
water or steam, does not cause a hazardous condition.
A
pressure gauge
must be fitted to allow the person filling
the system to see it to control the fill pressure. A gauge with
a range of 0 to 5 bar, or similar, is suitable.
A suitable
expansion vessel
must be fitted to the system. It
should be connected close to the inlet side of the circulating
pump. Its size must be calculated in accordance with BS
5449: pt1: 1997.
The
hot water cylinder
must be an indirect type and be sui-
table to operate at pressure of 0.35 bar over the pressure at
that of the safety valve, (3.35 bar minimum).
A single feed cylinder must not be used. A low level filling point
must be provided which incorporates a stopcock.
Provision should be made to replace system water losses by
either pre-pressurising the system or fitting a make up vessel
at the highest point of the system. BS 5376: pt2: 1976.
2.8.5 Fully pumped
The heating system design should be based on the following
information:
The appliance pressure drop details are given in Table 4.
A minimum flow rate corresponding to a heating differential
of 11°C must be obtained at all times.
A heating by-pass should be fitted to ensure the previous con-
dition is satisfied.
If thermostatic radiator valves are to be installed, at least one
radiator should be installed without a thermostatic valve
[usually the bathroom radiator].
The combined flow pipe (heating & hot water) should be con-
nected to the 22 mm flow pipe, which exits the appliance at
the rear, top right of the case (top manifold).
The combined return pipe (heating & hot water) should be
connected to the 22 mm return pipe, which enters the
appliance at the rear, top right of the case (bottom manifold).
6
ALTERNATIVE METHODS OF FILLING A SEALED SYSTEM
TABLE 6
Fig. 4
Vessel charge and initial system
pressure
Total water content of system if
using an 8 l (1.76 gal) expansion
vessel is used
To size the expansion vessel for
other system capacities multiply
the system volume by:
bar
psi
l
gal
0.5
7.3
87
19.1
.0833
1.5
21.8
44
9.7
.156
1.0
14.5
64
14.0
.109
SEALED WATER SYSTEM
Fig. 5
