General information
Operating principles
The CG is a wall-mounted condensing boiler with stainless steel counter flow twin heat exchangers (the CG 60 has a
single heat exchanger), pre-mix gas burner and integral flue products fan (refer Figs 1 and 2). When operating in
condensing mode with a flow of 50°C and a return of 30°C, it will give efficiencies of up to 109.5% (ncv). Gas is supplied
through a zero governor valve (2). The air intake fan (4) and venturi (3) accurately control the volumes of gas and air and
mix them prior to ignition. A small flame is held on the entire surface of the burner combustion head (6). This ensures
that there is optimum combustion at any point in the modulation range of the boiler.
System return water is passed through a number of tubes in the secondary (condensing) heat exchanger, and then the
primary heat exchanger. An integral boiler circulation pump (11) ensures an even and constant flow through the heat
exchanger - refer page 8. System circulating pumps should be hydraulically separated from the boiler(s) by a low
velocity header.
Key to Figs 1 & 2
1 Gas supply
2 Gas valve
3 Gas and air mixing by venturi
4 Fan unit
5 Ignition and flame ionisation electrodes
6 Burner head
7 First heat exchanger
8 Baffle plate
9 Second (condensing) heat exchanger
10 Flue gas outlet
11 Boiler circulation pump
12 Sound insulation panels
13 Electrical connection strip
14 Control display
Fig 1 Diagram of operating principles Fig 2 Cut-away CG boiler
1
2
3
4
5
6
7
9
10
8
11
12
13
14
EDS769/4 page2
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