Boiler Operation; Central Heating Mode; Domestic Hot Water Mode; Frost Protection - Baxi LUNA HT 1.450 Installation And Servicing Instructions

The boiler operating mode is controlled by the selector switch on the facia panel. When set to
in the Domestic Hot Water mode. When set to
Note:
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 i.e. storage water
is to the required temperature. This interruption in the central heating is only when the demand for hot water is present
and should not be noticed by the User.
If there is a call for heat, the pump will start to circulate the central heating water, operating the flow switch. The fan will
run; once the fan speed is reached 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 setpoint, 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. 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 minute delay before the burner will relight. If there is a demand for DHW during
the 3 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.
When a demand for hot water is made by an external tank, the pump starts and the burner lights at its mid output, then
increases to its maximum output. The burner output is varied to maintain the temperature of the hot water as that set
by the adjustable temperature selector. When the hot water is no longer required the burner is turned off and the boiler
immediately returns to the central heating mode.
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, providing the display is switched on. The boiler will operate until the water temperature in the system
reaches approximately 30 °C. Frost protection is for the boiler only and not for complete Central Heating.
If the display is switched on and the boiler has not operated for 24 hours for heating or hot water, the pump will operate
automatically for five minutes every 24 hours.
This device protects the primary exchanger from damage by not allowing the boiler to run in a LOW water pressure. The
LOW water condition occurs when the water pressure drops below approximately 7.25 psi (0.5 bar).
INSTALLATION AND SERVICING INSTRUCTIONS

13. BOILER OPERATION

( )
, it will operate in the Domestic Hot Water and Central Heating mode.

13.1 CENTRAL HEATING MODE

13.2 DOMESTIC HOT WATER MODE

13.3 FROST PROTECTION

13.4 PUMP

13.5 LWCO - LOW WATER CUT OFF

47
( )
, the boiler will only operate
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