Alpha CD25C Installation And Servicing Instructions page 20

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
water. Close the tap and the burner will go out.
6. Set the selector switch to
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
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
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.
5.6 FINAL COMMISSIONING
1. Allow the heating system to heat up, then balance the system to achieve the necessary temperature difference across the
heating flow and return pipes at the boiler and check the system volume and pressure. (Refer to Technical Data, Sections
2.2 and 2.8).
2. Turn off the boiler.
3. Thoroughly flush out the water pipework (refer to Section 3.9) and with no pressure in the boiler heating circuit, empty the cyclone
(if applicable) at it's drain point (see Fig. 13) of any debris. Clean the mains water inlet filter (see Fig. 13).
4. Re-pressurise the system as described in Section 5.1.
Alpha CD25C/28C/35C - Commissioning
20
(DHW only). Open a hot water tap, the main burner will light and the boiler will provide hot
(CH and DHW). The boiler will now run in the central heating mode. The pump will start,
(DHW only) and fully open a hot water tap.
(DHW and CH).
Do not
connect
here
Inlet gas
pressure
test point
Flue sample
point (marked 'F')
-
+
P2
-
Fig. 24
Do not connect here
Fig. 23
P1
+