Baxi Potterton 47-393-39 Appliance Operation, Central Heating Mode Fig, Frost Protection Mode

Central Heating Circuit

26

25

18 24 22

21

16

Fig. 2

1

27

		2
	3	4
		7
20	5	6
		8
		9
	23	11
		10
		17

15 14 13 12

3.0Appliance Operation

3.1Central 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).

3.2Domestic Hot Water Mode (Fig. 3)

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

Key

1	Primary Heat Exchanger	15 Domestic Hot Water Outlet
2	Burner
		16	Heating Flow
3	Ignition Electrodes
		17	Pressure Gauge
4	Flame Sensing Electrode
		18	Water Pressure Sensor
5	Gas Valve
		20	Fan
6	Pump
		21	Diverter Valve Assembly
7	Automatic Air Vent
		22	Diverter Valve Motor
8	Plate Heat Exchanger/Automatic By-pass
		23 Domestic Hot Water Flow Temperature Sensor
9	Flow Sensor with Filter & Regulator
		24	Safety Thermostat
10	Pressure Relief Valve
		25 Central Heating Temperature Sensor
11	Boiler Drain Point
		26	Expansion Vessel
12	Heating Return
		27 Heat Exchanger Air Vent
13	Cold Water Inlet On/Off Valve and Filter
14	Gas Inlet

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

Domestic Hot Water Circuit

27

		26	3	4
		20	5
		25
18		24
		22		9
	21		23

1

2

7

6

8

11

10

17

require resetting once the selector switch is set to either Position (i) or Position (ii).

3.3Frost 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.

3.4Pump 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.

16 15 14 13 12

Fig. 3

© Baxi Heating UK Ltd 2012 9