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1.14 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 84
3. All components of the system must be suitable for a working
pressure of 3 bar and a maximum design temperature of 110
C. Extra care should be taken in making all connections so
o
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
or
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 Table opposite.
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. Refer to Section
2.15 for filling detail.
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.
14
SECTION 1 - GENERAL
C.
o
Safety valve setting
Vessel charge pressure
System pre-charge pressure bar
System volume
(litres)
25
50
75
100
125
150
175
190
200
250
300
For other system volumes
multiply by the factor access
Water Flow Rate and Pressure Loss
Max CH Output
Water flow rate
Temperature Differential
Head available for
system
DOMESTIC HOT WATER
1. The domestic hot water service must be in accordance with
BS 5546 and BS 6700.
2. Refer to Table 1 for minimum and maximum working
pressures. In areas of low mains water pressures the
domestic hot water regulator may be removed from
the DHW flow turbine cartridge. Refer to Section 3.25.
The boiler will require the flow rate to be set to obtain a
temperature rise of 35
C at the tap furthest from the boiler.
o
3. The boiler is suitable for connection to most types of
washing machine and dishwasher appliances.
4. When connecting to suitable showers, ensure that:
a.
The cold inlet to the boiler is fitted with an approved
anti-vacuum or syphon non-return valve.
b. Hot and cold water supplies to the shower are of equal
pressure.
5. Hard Water Areas
Where the water hardness exceeds 200mg/litre, it is
recommended that a proprietary scale reducing device is
fitted into the boiler cold supply within the requirements of
the local water company.
IMPORTANT
Provision MUST be made to accommodate the expansion of
DHW contained within the appliance, if a non-return valve is fitted
to the DHW inlet, or a water meter with a non-return valve is
installed.
Cold water rising main and pipework in exposed areas need to
be suitably lagged to prevent freezing.
bar
3.0
bar
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
kW
24.2
l/min
17.3
(gal/min)
(3.8)
C
20
o
m.w.g.
3.4
(ft.w.g.)
(11.1)
Installation and Servicing
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