Boiler Operation; Central Heating Mode; Frost Thermostat; Pump - Baxi Luna 3 Comfort Series Installation And Servicing Instructions

6. boiler operation

to set the boiler operation, see the user's instructions manual.
Domestic hot water supply always takes priority over central heating. If a demand for hot water is required during a central
heating period, the boiler will automatically switch to the hot water mode until the demand is satisfied. This interruption in
the central heating is only when the demand for hot water is present and should not be noticed by the User.

6.1 - central heating mode

If there is a central heating demand, the pump will start to circulate the central heating water, operating the flow switch.
The fan will run; once the air pressure switch is proved the burner will light. The burner output then automatically adjusts
to suit the system demand; as the temperature of the water in the boiler approaches that set by the adjustable temperature
button +/-
(see the user's instruction manual), the burner output is reduced. When the set temperature is reached,
the burner is turned off and the fan stops. The pump continues to run for three minutes to remove residual heat build up
in the boiler. The burner will not relight for 3 minutes (it depends on the F18 parameter setting - see section 19). If the CH
sensor has not registered the pre-set temperature but the room thermostat is satisfied the burner is turned off, the fan
stops and the pump continues to run for three minutes. In this instance there is no 3 minutes delay before the burner will
relight. If there is a demand for DHW during the 1 minute burner delay, the boiler will operate to provide DHW until the tap
is closed; the boiler will then immediately revert to provide CH if there is a demand.
6.2 - domestic hot water mode
When a demand for hot water (by opening a hot tap, etc.) is sensed by the flow switch, the pump starts and the burner lights
at its middle output, increasing to its maximum output. Water in the boiler is then diverted from the central heating system
to the domestic hot water heat exchanger, heating the incoming mains water. The burner output is varied to maintain the
temperature of the hot water as that set by the adjustable temperature button +/- (see the user's instruction manual).
When the flow switch senses that the hot water is no longer required the burner is turned off and the boiler immediately
returns to the central heating mode.
In both modes the fan operates at full speed before the burner lights, remaining at that speed until the demand is sati-
sfied.

6.3 - frost thermostat

The boiler incorporates a built in frost thermostat which automatically turns on the boiler and pump if the water in the boiler
falls below 5°C. The boiler will operate until the water temperature in the system reaches approximately 30°C.

6.4 - pump

If the boiler has not operated for 24 hours for heating or hot water, the pump will operate automatically for five minutes
every 24 hours.
6.5 - lwc low water cut off
This device protects the primary exchanger from damage by not allowing the boiler to run in a LOW water condition.
InstructIons pertaInInG to tHe Installer 95.188.3 - GB
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