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4.6
CENTRAL HEATING SYSTEM - Fig. 4.5
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. 4.5. 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 EN 13831 with a capacity of 8 litres and pre-charged with air 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
unless separate zone valves have been installed.
Note: A drain tap should be installed at the lowest point
of the heating circuit and beneath the appliance.
4.7
FILLING THE CENTRAL HEATING SYSTEM - Fig. 4.6
The system design pressure (cold) should be set to 1.0 bar. This pressure is equivalent to a static head (see Fig. 4.5) of 10.2
metres of water.
The E-Tec Plus models have an integrated filling loop provided with the boiler connection group.
Fill the system using the two small black control valves opening one first and using the second to control the flow into the
system.
When the system is filled and vented to the correct pressure close both control valve taps. The temporary connection can
then be undone and slid back to disconnect the loop.
Drain valves (to BS 2879) must be fitted in the heating system to allow the system to be fully drained.
16
Alpha E-Tec Plus 28, 33 and 38 - General Boiler Information
Automatic
Boiler
air vent
casing
Heating
flow
Note: If the mains is fitted
Heating return
with a water meter, check
System
valves or loose jumper
drain tap
stop cock, then a DHW
expansion device must be
fitted.
Fig. 4.5
Fig. 4.6
Static head of system
Additional expansion
vessel (if required)
Filling point
DHW outlet
Mains water inlet
Filling control valves
Sliding temporary connection
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