Potterton Performa 28i, Installation And Servicing Instructions, Page: 7 / 48

3.0 Appliance Operation
7
NOTE: All delay timers mentioned in 3.1 and 3.2
are overridden by domestic hot water demand.
3.1 Central Heating Mode (Fig. 2)
1. With a demand for heating, the pump circulates
water through the primary circuit. At a pre-
determined flow rate 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
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 30 seconds (Pump Overrun).
5. If there is no other demand the pre-heat
function will operate if switched on (see Section
3.2).
3.2 Domestic Hot Water - Preheat Mode
(Fig. 3)
1. With the pre-heat function switched on (pre-
heat control fully clockwise), priority is given to the
replenishment of the pre-heat store. The DHW
mode neon ( ) will flash during this function.
2. The diverter valve remains in the DHW priority
position. This allows the pump to circulate hot
water to the store and back to the primary heat
exchanger via the bypass pipe.
3. The automatic ignition sequence commences
after approximately 25 seconds and the burner
will light.
4. When the store reaches the desired
temperature the burner is extinguished. The pump
continues to run for a period of 30 seconds.
5. Following a demand for domestic hot water or
the end of a central heating ON period, the pre-
heat function restarts.
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19
16 15 14 13 12
10
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11
8
17
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20 22
19
28
26
5 6
7
2
3 4
1
25
24
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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
14 Gas Inlet
15 Domestic Hot Water Outlet
16 Heating Flow
17 Pressure Gauge
18 Hydraulic Pressure Sensor Microswitch
19 Automatic By-Pass
20 Hydraulic Pressure Sensor
21 Diverter Valve Assembly
22 Domestic Hot Water Flow Priority Assembly
23 Domestic Hot Water Flow Priority Microswitch
24 Safety Thermostat
25 Central Heating Temperature Sensor
26 Expansion Vessel & Pre-Heat Store
27 Domestic Hot Water Temperature Sensor
Key
Central Heating Mode
Fig. 2
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19
16 15 14 13 12
10
9
11
8
17
21
23
20 22
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28
26
5 6
7
2
3 4
1
25
24
18
Domestic Hot Water - Preheat Mode
Fig. 3