Appliance Operation - Baxi Combi 130 HE Installation & Servicing Instructions Manual

3.0 Appliance Operation

NOTE: All delay timers mentioned in 3.1 and 3.2
are overridden by domestic hot water demand.
3.1 Central Heating Mode
1. With a demand for heating, the pump circulates
water through the primary circuit. At a flow rate of
approximately 4.5 l/hr the central heating flow
switch operates, initiating the ignition sequence.
2. The burner ignites at low rate, then the gas
control system modulates the heat input to maintain
the heating temperature measured by the
thermistor sensor.
3. When the boiler reaches temperature, a 1 minute
pump overrun occurs followed by 3 minutes
anticycle. If the flow temperature is low enough the
burner will then relight automatically otherwise
pump overrun and anticycle will occur again.
3.2 Domestic Hot Water Mode
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 and the 3-way valve will 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 return thermistor.
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.
3.3 Boiler Frost Protection
1. The boiler incorporates an automatic integral
frost protection feature (see section 10.4). It will
operate in both summer and winter modes. If the
boiler temperature falls below 8°C (± 5°) then the
boiler will fire until a temperature of 15°C (± 5°) is
reached.
3.4 System Frost Protection Mode
1. The boiler incorporates an integral system frost
protection feature. This can be activated (see
section 10.4) if required. To monitor system
temperature the boiler will switch on the pump
every four hours in both summer and winter modes.
If water returned to the boiler is below 8°C (± 5°)
the boiler frost protection mode is automatically
activated. Due consideration should be taken to the
siting of the appliance when using this option. It
may be preferable to fit an external frost thermostat
to the system. In this instance the integral system
frost protection feature need not be activated.
3.5 Pump Protection
1. The control system continually monitors the time
since the pump last operated. This will result in the
pump being run for 1 minute if it has not run in the
last 24 hours to prevent seizure.
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