Baxi Potterton 30 HE Appliance Operation, Central Heating Mode Fig, Domestic Hot Water Mode Fig

						1
	Central Heating Circuit
							28
						2
					3	4	7
		26
					5	6
	25					8
	24
	23					9
	22			27			11
	21		17			10
	20	18
	16		15	14		13	12
		19
	Fig. 2
Key
1	Primary Heat Exchanger			15	Domestic Hot Water Outlet
2	Burner			16	Heating Flow
3	Ignition Electrode			17	Pressure Gauge
4	Flame Sensing Electrode			18	Hydraulic Differential Pressure Sensor Microswitch
5	Gas Valve			19	Automatic By-Pass
6	Pump			20	Hydraulic Differential Pressure Sensor
7	Automatic Air Vent			21	Diverter Valve Assembly
8	Plate Heat Exchanger			22	Domestic Hot Water Flow Priority Assembly
9	Flow Sensor with Filter			23	Domestic Hot Water Flow Priority Microswitch
10	Pressure Relief Valve			24	Safety Thermostat
11	Boiler Drain Point			25	Central Heating Temperature Sensor
12	Heating Return			26	Expansion Vessel
13 Cold Water Inlet On/Off Valve and Filter				27	Domestic Hot Water Temperature Sensor
14	Gas Inlet			28	Secondary Heat Exchanger
						1
	Domestic Hot Water Circuit
							28
						2
					3	4	7
		26
					5	6

25

	24				8
23				9
22					11
21		17	27
					10
	20
16	18	15	14	13	12
	19

Fig. 3

3.0 Appliance Operation

NOTE: All delay timers mentioned in 3.1 and 3.2 are

overridden by domestic hot water demand.

3.1Central 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 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 DHW flow switch which requests 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 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 (if fitted) will 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.

8© Baxi Heating UK Ltd 2007