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Central Heating Circuit
26
25
24
23
22
21
20
18
16
19
Fig. 2
Key
1
Primary Heat Exchanger
2
Burner
3
Ignition Electrode
4
Flame Sensing Electrode
5
Gas Valve
6
Pump
7
Automatic Air Vent
8
Plate Heat Exchanger
9
Flow Sensor with Filter
10 Pressure Relief Valve
11 Boiler Drain Point
12 Heating Return
13 Cold Water Inlet On/Off Valve and Filter
Domestic Hot Water Circuit
26
25
24
23
22
21
20
18
16
19
Fig. 3
6
1
2
3
4
5
6
9
27
17
10
15
14
13
14 Gas Inlet
15 Domestic Hot Water Outlet
16 Heating Flow
17 Pressure Gauge
18 Hydraulic Differential Pressure Sensor Microswitch
19 Automatic By-Pass
20 Hydraulic Differential Pressure Sensor
21 Diverter Valve Assembly
22 Domestic Hot Water Flow Priority Assembly
23 Domestic Hot Water Flow Priority Microswitch
24 Overheat Thermostat
25 Central Heating NTC Sensor
26 Expansion Vessel
27 Domestic Hot Water NTC Sensor
1
2
3
4
5
6
9
27
17
10
15
14
13
NOTE: All delay timers mentioned in 3.1 and
3.2 are overridden by domestic hot water
demand.
3.1
1. With a demand for heating, the pump circulates
7
water through the primary circuit. At a flow rate of
approximately 125 l/hr the central heating flow
switch operates, initiating the ignition sequence.
2. The main burner ignites at low rate, then the
gas valve controls the gas rate to maintain the
heating temperature measured by the thermostat
8
sensor.
3. When the flow temperature exceeds the setting
temperature, a 3 minute delay occurs before the
burner relights automatically (anti-cycling). The
11
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).
12
3.2
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 DHW flow
switch which causes 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 thermostat 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 (if fitted) will require
resetting once the selector switch is set to
7
either the DHW position or CH position.
3.3
1. The frost protection mode is integral to the
appliance and functions only with the selector
8
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
11
incorporated by using a system frost thermostat.
3.4
12
1. With the selector switch (see Section 2.1) in
either the central heating or central heating and
hot water position the pump will automatically
operate for 1 minute in every 24 hours to prevent
sticking
3.0 Appliance Operation
Central Heating Mode (Fig. 2)
Domestic Hot Water Mode (Fig. 3)
Frost Protection Mode
Pump Protection
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