Adjustment And Safety Devices - Baxi Mainfour 24-24F Operating And Installation Instructions

22. ADJUSTMENT AND SAFETY DEVICES

This boiler has been designed in full compliance with European reference standards and, in particular, it is fitted with the following:
• Air pressure switch (model 24 F)
This device only allows the burner to ignite if the exhaust flue duct is in perfect working order.
In the event of one or more of the following faults:
• flue terminal obstructed
• venturi tubes obstructed
• fan blocked
• venturi tube connection - pressure switch tripped
the boiler remains on standby and error code E03 is displayed (see table in section 10).
• Fumes thermostat (model 24)
This device, the sensor of which is positioned to the left of the fumes hood, interrupts the flow of gas to the main burner if the flue is
obstructed and/or there is no draught.
In these conditions the boiler shuts down and displays error code E03 (section 10).
After eliminating the problem, it is possible to reignite by holding down the ( ), button for at least 2 seconds.
It is forbidden to disable this safety device
• Safety thermostat
Thanks to a sensor placed on the heating delivery line, the thermostat interrupts the flow of gas to the burner if the water in the pri-
mary circuit overheats. In these conditions, the boiler is blocked and only after the fault has been eliminated can it be ignited again by
pressing ( ), button for at least 2 seconds.
It is forbidden to disable this safety device
• Flame ionisation detector
The flame sensing electrode, located on the right-hand side of the burner, guarantees safety of operation in case of gas failure or
incomplete ignition of the burner.
In these conditions, the boiler is blocked after 3 ignition attempts.
Press the ( ), for at least 2 seconds to re-establish normal operating conditions.
• Hydraulic pressure switch
This device allows the main burner to be ignited only if system pressure is higher than 0.5 bars.
• Pump overrun for heating circuit
The electronically-controlled pump post-circulation function lasts 180 seconds and is enabled, in the heating mode, if the ambient
thermostat causes the burner to go out.
• Pump overrun for DHW circuit
The electronically-controlled pump post-circulation function lasts 30 seconds and is enabled, in the DHW mode, if the probe causes
the burner to go out.
• Frost protection device (heating)
The electronic boiler management system includes a "frost protection" function for the heating system which, when delivery tempe-
rature falls below 5°C, operates the burner until a delivery temperature of 30°C is reached. This function is enabled when the boiler
is switched on, the gas supply is open and the system is correctly pressurised.
• Water not circulating in primary circuit (pump probably blocked)
If there is insufficient or no water circulating in the primary circuit, the boiler blocks and the error code E25 is shown on the display
(section 10).
• Anti-block pump function
If no heat demand is received for 24 consecutive hours, in the heating mode, the pump will automatically start and operate for 10
seconds.
This function is operative when the boiler is powered.
• Hydraulic safety valve (heating circuit)
This device is set to 3 bar and is used for the heating circuit .
Connect the safety valve to a drain tap. Do not use it to drain the heating circuit.
NOTE:
domestic hot water is guaranteed even if the NTC sensor develops a fault. In this case, temperature is controlled by the delivery sensor.
INSTRUCTIONS FOR FITTERS
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71.07144.01 - EN