9
3.0 Appliance Operation
© Baxi Heating UK Ltd 2012
3.1
Central Heating Mode (Fig. 2)
1. With a demand for heating, the pump circulates water
through the primary circuit.
2. Once main burner ignites the fan speed controls the gas
rate to maintain the heating temperature measured by the
temperature sensor.
3. 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.
4. When the demand is satisfied the burner is extinguished
and the pump continues to run for a period of 3 minutes
(Pump Overrun).
3.2
Domestic Hot Water Mode (Fig. 2)
1. Priority is given to the domestic hot water supply. A
demand at a tap or shower will override any central heating
requirement.
2. The flow of water will operate the Hall Effect Sensor
which requests the 3 way valve to change position. This will
allow the pump to circulate the primary water through the
DHW plate heat exchanger.
3. The burner will light automatically and the temperature of
the domestic hot water is controlled by the temperature
sensor.
4. When the domestic hot water demand ceases the burner
will extinguish and the diverter valve will remain in the
domestic hot water mode, unless there is a demand for
central heating.
IMPORTANT:
When the selector switch is in the ‘0’
(Off) position the electrical supply to the boiler is isolated.
The boiler will not operate and the integral timer will
require resetting once the selector switch is set to either
Position ( ) or Position ( ).
3.3
Frost Protection Mode
1. The frost protection mode is integral to the appliance and
functions only with the selector switch (see Section 2.1) in
the domestic hot water and central heating 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.
3.4
Pump Protection
1. With the selector switch (see Section 2.1) in either the
central heating or central heating and domestic hot water
position, the pump will automatically operate for 1 minute in
every 24 hours to prevent sticking.
1
2
4
5 6
7
8
9
10
11
12
13
14
15
16
17
18
21
22
26
3
1
Primary Heat Exchanger
2
Burner
3
Ignition Electrodes
4
Flame Sensing Electrode
5
Gas Valve
6
Pump
7
Automatic Air Vent
8
Plate Heat Exchanger
9
DHW Flow Sensor (‘Hall Effect’ Sensor)
10 Pressure Relief Valve
11 Boiler Drain Point
12 Heating Return
13 Cold Water Inlet On/Off Valve and Filter
14 Gas Inlet
15 Domestic Hot Water Outlet
16 Heating Flow
17 Pressure Gauge
18 Water Pressure Sensor
20 Fan
21 Diverter Valve Assembly
22 Diverter Valve Motor
23 Domestic Hot Water Flow Temperature Sensor
24 Safety Thermostat
25 Central Heating Temperature Sensor
26 Expansion Vessel
27 Heat Exchanger Air Vent
28 By-pass Valve
Key
Boiler Schematic
Fig. 2
23
20
27
25
24
28
