9
3.0 Appliance Operation
© Baxi Heating UK Ltd 2011
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3
Key
1
Heat Exchanger
2
Burner
3
Ignition Electrode
4
Flame Sensing Electrode
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Gas Valve
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Pump
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Automatic Air Vent
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Pressure Relief Valve
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Boiler Drain Point
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Gas Inlet
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Boiler Flow
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Boiler Return
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Pressure Gauge
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Automatic By-Pass
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Water Pressure Sensor
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Safety Thermostat
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Temperature Sensor
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Expansion Vessel
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Return Temperature Sensor
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Fan
Boiler Primary Circuit
Fig. 2
20
3.1
Operating Mode (Fig. 2)
1. With a demand for heating or hot water, the pump
circulates water through the primary circuit. If the pressure is
at least 0.5 bar and the ignition sequence will start.
2. When the flow temperature exceeds the setting
temperature, a 3 minute delay occurs before the burner
relights automatically (anti-cycling). The pump continues to
run during this period.
3. When the demand is satisfied the burner is extinguished
and the pump continues to run for a period of 3 minutes
(Pump Overrun).
IMPORTANT: When the selector switch is in the ‘0’
(Off) position the electrical supply to the boiler is
isolated. The boiler will not operate.
3.2
Frost Protection Mode
1. The frost protection mode is integral to the appliance and
functions when the selector switch (see Section 2.1) is in the
ON position ( ). If the system temperature falls below
5° C then the boiler will fire on its minimum setting until a
flow temperature of 30° C is reached. Further protection
can be incorporated by using a system frost thermostat.
3.3
Pump Protection
1. With the selector switch (see Section 2.1) in the ON
position ( ) the pump will automatically operate for 1
minute in every 24 hours to prevent sticking.
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