Appliance Operation - Baxi Maxflow Combi WM Installation And Servicing Instructions

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19 22
18
Fig. 4
17 16
Key
1 Main Heat Exchanger
2 Automatic Air Vent
3 Burner
4 Ignition Electrode
5 Flame Sensing Electrode
6 Differential Pressure Switch
7 Gas Valve
8 Primary Flow Temperature Sensor
9 3-Way Diverter Valve
10 Pump
11 By-Pass
12 Pressure Gauge
13 Gas Inlet
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19 22
18
Fig. 5
17 16
6
21
Central Heating Circuit
1
23
24
3
25
5 4
6
7
8
9
M
11
26
12
15 14 13
14 Heating Flow
15 Heating Return
16 Cold Water Inlet
17 Domestic Hot Water Outlet
18 Flow Restrictor
19 Hot Water Storage Temperature Sensor
20 Temperature/Pressure Relief Valve
21 Storage Cylinder
22 Secondary Heat Exchanger
23 Central Heating Expansion Vessel
24 Safety Limit Thermostat
25 Central Heating Pressure Relief Valve
26 Removable Filter in Return Manifold
21
Domestic Hot Water Circuit
1
23
24
3
25
5 4
6
7
8
M
9
11
26
12
15 14 13

3.0 Appliance Operation

3.1 Boiler Operation
1. The boiler operating mode is controlled by the
selector switch on the control panel. When set to
it will operate in the Domestic Hot Water and
Central Heating modes. For Domestic Hot Water only
the selector switch should be set to
2. Domestic hot water supply always takes priority
over central heating. If a demand for hot water is
required during a central heating period, the boiler
will automatically switch to hot water mode until the
demand is satisfied i.e. storage water has reached
2
the set temperature. Interruption to the central
heating only occurs when there is a demand for hot
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water and should not be apparent to the User.
3. Central Heating Mode (Fig. 4)
If there is a call for central heating the diverter valve
operates and the pump circulates the primary heating
water, operating the differential pressure switch. The
fan will run at full speed; once the air pressure switch
has been proved the burner will light. The burner
output then automatically adjusts to suit the system
demand; as the temperature of the heating water in
the boiler approaches that set by the adjustable
central heating control knob the burner output is
reduced. When this set temperature is reached, the
burner extinguishes and the fan stops. The pump
continues to run for 3 minutes to prevent residual
heat build up in the boiler. The burner will not relight
for 3 minutes unless there is a demand for domestic
hot water during this period.
4. Domestic Hot Water Mode (Fig. 5)
When there is a demand for hot water (temperature
of stored hot water is below that set by the
thermostat), the pump will start to circulate the
primary heating water, operating the differential
pressure switch. The fan will run at full speed; once
the air pressure switch has been proved the burner
will light. The burner output then automatically
adjusts to suit the demand required to raise the
temperature of the domestic hot water within the
store to the temperature set by the adjustable
domestic hot water control knob. When this
temperature is reached the burner extinguishes and
the fan stops. The pump continues to run for 3
minutes to prevent residual heat build up in the boiler.
When the hot water demand has been satisfied, the
3-way diverter valve operates to divert the primary
heating water to the central heating, if the selector is
set to
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 (if fitted) will require resetting once the selector
switch is turned to either the DHW or CH position
3.2 Frost Protection Mode
1. The frost protection feature will operate when the
2
selector switch is in the central heating and domestic
hot water mode.
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The gas and electrical supplies to the boiler must be
on and the system pressure between 0.5 and 2.5 bar.
2. If the system temperature falls below 5° C, then
the boiler will fire until the water temperature has
been raised.
3. Further frost protection can be incorporated by
using a frost thermostat to protect the whole system.
3.3 Pump Protection
1. With the selector switch in either operating position
the pump will automatically operate for 1 minute in
every 24 hours to prevent sticking.
.
and there is a C.H. demand.