19
5.3 TEST FOR GAS SOUNDNESS AND PURGE THE SUPPLY
1. With the boiler gas service cock closed (slot at right angles to valve). Pressure test the gas supply and inlet pipework
connection to the boiler gas service cock for soundness in accordance with BS 6891.
2. Loosen the gas inlet pressure test point screw on the gas valve (see Fig. 23). Ensure the gas supply is on and open the
boiler service cock to purge in accordance with BS 6891.
3. Retighten the test point screw and test for gas soundness. Close the boiler gas service cock.
5.4 INITIAL LIGHTING - Refer to Fig. 22
1. Ensure that the gas and electrical supplies to the boiler are off and that the mains water inlet valve and the central heating
flow and return valves are open.
2. Turn on the gas and electrical supplies to the boiler.
3. Ensure all external controls are calling for heat.
If the optional Clock is fitted, refer to the User's instructions, set the time and ensure the Clock is in an 'on' mode.
4. Set the hot water and central heating thermostats to maximum.
5. Set the selector switch to
(DHW only). Open a hot water tap, the main burner will light and the boiler will provide hot
water. Close the tap and the burner will go out.
6. Set the selector switch to
(CH and DHW). The boiler will now run in the central heating mode. The pump will start,
the fan will start and the main gas valve solenoid will open allowing the main burner to light.
5.5 CHECK THE BURNER PRESSURES - Figs. 23, 24
Turn the boiler off. Remove the two pressure test point screws at the top of the boiler and connect a differential pressure gauge
to P1 and P2 as shown in Fig 24. Allow the boiler to run for 10 minutes and check the differential burner pressures.
Hot water mode
1. Set the selector switch to (DHW only) and fully open a hot water tap.
2. The burner will light at the ignition rate and the burner pressure will
increase to maximum.
3. Gradually close the hot tap and check that the burner pressure decreases
to its minimum. Fully open the tap and check that the burner pressure
increases. Close the tap and check that the burner goes off.
Note: The burner pressure settings have been factory set and do not
require adjusting. If incorrect, check that the inlet gas pressure is 20 mbar.
If the inlet gas pressure is not 20 mbar, either the pipework is too small or
the gas supply to the house is insufficient, in which case contact your gas
supplier.
Central heating mode
1. Set the selector switch to (DHW and CH).
2. The burner will light at the ignition rate and will increase to
the factory pre-set maximum output after 1 minute.
3. Turn off the boiler. Disconnect the pressure gauge and
tighten the test point screws.
Test for gas soundness using suitable leak detection fluid.
Note: Refer to Technical Data, Section 2.1 for the required
differential burner pressures.
Alpha CD24C/32C - Commissioning
Fig. 23
Fig. 24
Differential
Burner
pressure
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