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2
SySteM ReqUiReMentS - Central Heating
notes
a. The method of filling, refilling, topping up or flushing sealed
primary hot water circuits from the mains via a temporary hose
connection is only allowed if acceptable to the local water
authority.
b. Antifreeze fluid, corrosion and scale inhibitor fluids suitable for
use with boilers having aluminium heat exchangers may be used
in the central heating system.
General
1. The installation must comply with all relevant national and local
regulations.
2. The installation should be designed to work with flow
temperatures of up to 86
3. All components of the system must be suitable for a working
pressure of 3 bar and temperature of 110
be taken in making all connections so that the risk of leakage
is minimised.
The following components are incorporated within the
appliance:
a.
Circulating pump.
b. Safety valve, with a non-adjustable preset lift pressure of
3 bar.
c.
Pressure gauge, covering a range of 0 to 4 bar.
d. An 8-litre expansion vessel, with an initial charge pressure
of 0.75 bar.
4. 'Make-up' Water. Provision must be made for replacing water
loss from the system, either :
a.
From a manually filled 'make-up' vessel with a readily
visible water level. The vessel should be mounted at
least 150mm above the highest point of the system and
be connected through a non-return valve to the system,
fitted at least 150mm below the 'make-up' vessel on the
return side of the radiators.
b. Where access to a 'make-up' vessel would be difficult, by
pre-pressurisation of the system.
The maximum cold water capacity of the system should
not exceed 143 litres, if not pressurized. However, if
the system is to be pressurized, the efficiency of the
expansion vessel will be reduced and a larger vessel
(or smaller system volume) may be necessary. If the
capacity of the vessel is not considered sufficient for
this, or for any other reason, an additional vessel MUST
be installed on the return to the boiler.
Guidance on vessel sizing is given in Frame 2.
5. filling
The system may be filled by the following method:
Where the mains pressure is excessive a pressure reducing
valve must be used to facilitate filling.
a.
Thoroughly flush out the whole system with cold water.
b. Fill and vent the system until the pressure gauge
registers 1bar and examine for leaks.
c.
Check the operation of the safety valve by raising the
water pressure until the valve lifts. This should occur
within 0.3bar of the preset lift pressure.
d. Release water from the system until the
minimum system design pressure is reached;
1.0 bar if the system is to be pre-pressurised.
i-mini -
Installation and Servicing
C.
o
C. Extra care should
o
or
general
Safety valve setting
Vessel charge pressure
System pre-charge pressure bar
System volume
(litres)
100
125
150
175
190
200
250
300
For other system volumes
multiply by the factor across
Water Flow Rate and Pressure Loss
Max CH Output
Water flow rate
Temperature Differential
Head available for
system
CH Return
bar
bar
25
50
75
kW
24.2
(Btu/h)
(82,600)
l/min
17.3
(gal/min)
(3.8)
C
o
(
F)
(36)
o
m.w.g.
(ft.w.g.)
(11.1)
Hose unions
Temporary hose
(disconnect after filling)
3.0
0.5 to 0.75
None
1.0
Expansion vessel
volume (litres)
1.6
1.8
3.1
3.7
4.7
5.5
6.3
7.4
7.8
9.2
9.4
11.0
10.9
12.9
11.9
14.0
12.5
14.7
15.6
18.4
18.8
22.1
0.063
0.074
20
3.4
Mains
water supply
Additional
stop valve
Double check valve
assembly
(
)
note direction of flow
13
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