Alpha InTec2 25XE Installation And Servicing Instruction page 13

3.7 CENTRAL HEATING SYSTEM - Fig. 3.5
The boiler is designed for use in a sealed central heating system in accordance with the requirements of BS EN 12828 and BS 6798.
The system should be designed to operate with flow temperatures of up to 90°C. When designing the system, the pump
head, expansion vessel size, mean radiator temperature, etc. must all be taken into account. Refer to the pump performance
table for guidelines.
System volume - The expansion vessel incorporated into the boiler is suitable for a sealed heating system with a maximum
water content of 80 litres (18 gal). Above 80 litres, consideration should be given to fitting an additional expansion vessel
fitted in the position shown in Fig. 32.5. To check correct operation of the expansion vessel(s) the system pressure should not
be more than 2.5 bar when the system is at maximum operating temperature (for further guidance refer to BS 7074:1).
The boiler is supplied with the following components built in:-
Pressure gauge - To indicate the system pressure to be maintained.
Expansion vessel - Conforming to BS 4814 with a capacity of 8 litres and pre-charged to a pressure of 1.0 bar.
By-pass - The boiler incorporates an automatic by-pass, therefore an automatic by-pass is not required for the system.
Note: A drain tap should be installed at the lowest point
of the heating circuit and beneath the appliance.
3.8 FILLING THE CENTRAL HEATING SYSTEM - Fig. 3.6
The system design pressure (cold) should be set to 1.0 bar. This pressure is equivalent to a static head (see Fig. 3.5) of 10.2
metres of water.
Provision must be made for filling the system. This is done by the use of a filling loop. See Fig. 3.6. A filling loop is not
supplied with this boiler.
Filling of the system must be carried out in a manner approved by the local Water Undertaking. Where allowed, the system
may be filled via a temporary connection as shown in Fig. 3.6. After filling, always disconnect the flexible hose of the filling
loop.
All fittings used in the system must be able to withstand pressures up to 3 bar.
Drain taps (to BS 2879) must be used to allow the system to be completely drained.
Heating
flow
Heating return
System
drain tap
Fig. 3.5
Hose
unions
Heating circuit
return
Stop
valve
Filling loop
temporarily connected
Fig. 3.6
Alpha InTec² 25XE and 28XE - General Boiler Information
Automatic
Boiler
air vent
casing
Note: If the mains is fitted with water
meter, check valves or loose jumper
stop cock, then a DHW expansion
device must be fitted.
Double check
valve assembly
Mains
water
Stop supply
valve
Test cock
Static head of system
Additional expansion
vessel (if required)
Filling point
DHW outlet
Mains water inlet
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