Technical data

17
The boiler operation is controlled by the selector switch on the facia panel. When set to ON, it will provide central heating.
6.1 CENTRAL HEATING
If there is a call for heat, the pump will start to circulate the central heating water. The fan will run at full speed; once the air
pressure switch is proved the burner will light. The burner output then automatically adjusts to suit the system demand; as the
temperature of the water in the boiler approaches that set by the adjustable central heating thermostat (see Fig. 15), the burner
output is reduced. When the set temperature is reached, the burner is turned off. The fan continues to run for 20 seconds and
the pump continues to run for three minutes to remove residual heat build up in the boiler before allowing the burner to relight. If
the CH sensor has not registered the pre-set temperature but the room thermostat is satisfied the burner is turned off. The fan
continues to run for 20 seconds and the pump continues to run for 30 seconds. In this instance there is no 3 minute delay
before the burner will relight.
Note: If the system pressure is very low, the primary pressure switch will prevent the boiler from operating.
6.2 FROST THERMOSTAT
The boiler incorporates a built in frost thermostat which automatically turns on the boiler and pump if the water in the boiler falls
below 8°C, providing the electrical supply is on and the selector switch set to . The boiler will operate until the water
temperature in the system reaches approximately 40°C.
6.3 PUMP
If the electrical supply is on and the boiler has not operated for 24 hours, the pump will operate automatically for five minutes
every 24 hours.
6.4 INDICATOR NEONS
When neon A (red) and neon B (yellow) are illuminated, the following conditions apply:-
Neon
B Flashing very slowly (every 5 seconds) - Electricity supply to the boiler is on.
B Illuminated continuously - Indicates the burner is alight.
B Flashing on and off - Temperature sensor fault.
A Flashing on and off - Overheat thermostat has operated. Rotate selector switch to the reset position (3) to reset.
A Illuminated continuously - Burner has failed to light. Rotate the selector switch to the reset position (3) and the
ignition sequence will restart after a delay of about 30 seconds.
A and B Flashing on and off at the same time - Blocked flue or fan fault.
A and B Flashing on and off alternatively - System pressure is very low and re-pressurisation is required.
A Illuminated continuously and B flashing - Pump fault or restricted flow.
Alpha SY9-24 - Boiler Operation
6 BOILER OPERATION