1. CHECKING APPLIANCE OPERATION
When carrying out any repairs or servicing to the appliance, the relevant commissioning procedure must be undertaken to ensure the continued safe operation of the appliance. Particular attention should be made to ensure gas tightness, water tightness, and the electrical integrity of the appliance.
2.APPLIANCE MODES OF OPERATION NOTICE
There must be sufficient system water pressure min 7 psi (0.5 bar) to ensure the water pressure switch is activated. If there is insufficient system pressure the pump and fan will be prevented from operating and the low-pressure fault code will be displayed.
The 2-digit display can show several different modes of operation.
3.SELECTOR SWITCH IN THE OFF/STAND BY POSITION When the selector switch is in the Off/reset position, the following functions are active.
Active functions:
-Freeze protection system
-Pump anti-seize
4. ON-BOARD FUNCTIONS
-THERMOREGULATION: When an outdoor air sensor is connected to the appliance, the electronic circuitry will automatically adjust the flow outlet temperature to suit local weather conditions in order to maintain comfort and efficiency. A specific operating curve that is most suited to the system type and geographical area can also be selected (Fig. 65).
-CO FUNCTION: the CO function when activated, will allow the appliance to run at maximum and minimum output while a combustion analysis check is being carried out. While the CO function is active, all other functions are disabled (minimum power operating period, anti-cycle, set-point, etc). Once enabled, the CO function will remain active for a 15-minute period, or until the function is manually deactivated (refit and rotate in any direction the main selector switch).
-FREEZE PROTECTION: This function is only active when there are no requests for heating or DHW. If the temperature drops below 43°F (6°C), the boiler will operate on minimum power until the temperature of the primary thermistor reaches 95°F (35°C).Thereafter the pump & fan will post-purge for 30-seconds.
-ANTI-CYCLE FUNCTION: The anti-cycle function ensures the burner remains switched off for at least 3-minutes after the set-point hysteresis (set-point + 9°F (5°C)).
-PUMP ANTI-SEIZE FUNCTION: When there has been no heating or DHW request for 24-hours, the anti-seize cycle is activated.The pump will be activated for a period of 30-seconds.
-ACTUATOR ANTI-SEIZE FUNCTION: When there has been no heating or DHW request for 24-hours, the anti-seize cycle is activated. The divertor valve actuator (3-way valve) will cycle briefly to the heating position, and then back to the DHW position.
5. HEATING MODE
With the selector switch in the ON position (
- 
- 
F ) and any additional controls (time clock, programmer, room thermostat, etc,) calling for heat, the appliance will operate in the heating mode. The pump and fan will be activated via the flow temperature sensor. When the fan is sensed to be operating correctly (blower signal), the ignition sequence commences. Ignition is sensed by the electronic circuitry to ensure flame stability at the burner. Once successful ignition has been achieved, the electronic circuitry increases the gas rate to 75% of the MAX Heating (set by the corresponding HTG trimmer) for a period of 15 minutes. The speed of the fan and therefore the output of the boiler is determined by the temperature of the water sensed by the flow temperature sensor, consequently a high temperature at the flow sensor results in a lower fan speed. As the water temperature increases, the temperature sensors – located on the flow pipe of the boiler – reduce the fan speed via the electronic circuitry. Depending on the load, either the water temperature will continue to rise until the set point is achieved or the water temperature will fall whereby fan speed will increase relative to the output required. When the boiler has reached the set point (+ hysteresis), the burner will switch off. The built-in anti-cycle device prevents the burner from re-lighting for approximately 3-minutes. When the temperature of the flow sensor falls below the set point (- hysteresis), the burner will re-light.
NOTICE: If the spark/sensing electrode does not sense ignition the appliance will re-attempt ignition a further 4-times then go to lockout. When the set-point has been reached (the position of the heating temperature selector) as measured at the primary thermistor, the appliance will begin the modulation phase whereby the fan and gas valve will continuously modulate to maintain the set-point.
If the temperature continues to rise and exceeds the set- point by 9°F (5°C) (hysteresis), the burner will shut down. A new ignition sequence will be enabled when the 3- minute anti-cycle has been performed and the temperature at the primary thermistor has dropped 9°F (5°C) (hysteresis) below the set-point.
NOTICE: When the request for heating and/or hot water has been satisfied, the appliance pump and fan may continue to circulate to dissipate any residual heat within the appliance.
6. DHW MODE
With the selector switch in either the hot water only or heating & hot water position, the appliance will operate in the hot water mode whenever a tank sensor/thermostat is in request. If there is a request the pump and fan will be activated via the flow tempe- rature sensor. When the fan is sensed to be operating correctly (blower signal), the ignition sequence commences. Ignition is sensed by the electronic circuitry to ensure flame stability at the burner. Once successful ignition has been achieved, the electronic circuit allows the gas rate to achieve the modulation value.
