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Central Heating Circuit
1
2
9
8
12
14
15 16
17
21
Fig. 4
Key
1
Heating Flow
2
Central Heating Pressure Relief Valve
3
Heating Return
4
Domestic Hot Water Outlet
5
Cold Water Inlet
6
Gas Inlet
7
By-Pass
8
Safety Limit Thermostat
9
Primary Flow Temperature Sensor
10 3-Way Diverter Valve
11 Hot Water Storage Temperature Sensor
12 Main Heat Exchanger
Domestic Hot Water Circuit
1
2
9
8
12
14
15 16
17
21
Fig. 5
6
3
4
5
7
10
M
11
18
19
22
23
13 Temperature/Pressure Relief Valve
14 Central Heating Expansion Vessel
15 Ignition Electrode
16 Burner
17 Differential Pressure Switch
18 Flame Sensing Electrode
19 Automatic Air Vent
20 Gas Valve
21 Pressure Gauge
22 Pump
23 Storage Cylinder Heating Coil
24 Storage Cylinder
3
4
5
7
10
M
11
18
19
22
23
3.0 Appliance Operation
6
3.1
1. The boiler operating mode is controlled by the
selector switch on the control panel. When set to
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
13
will automatically switch to hot water mode until the
demand is satisfied i.e. storage water has reached
the set temperature. Interruption to the central
heating only occurs when there is a demand for hot
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
20
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
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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
6
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
13
1. The frost protection feature will operate when the
selector switch is in the central heating and domestic
hot water mode.
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
20
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.
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3.3
1. With the selector switch in either operating position
the pump will automatically operate for 1 minute in
every 24 hours to prevent sticking.
Boiler Operation
it will operate in the Domestic Hot Water and
and there is a C.H. demand.
Frost Protection Mode
Pump Protection
.
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