Sequence Of Operation; Central Heating Mode - Ariston Benchmark System A 24 RFF Installation And Servicing Instructions

16. Sequence of operation

Central Heating Mode

Activation of the time clock and/or room thermostat starts the boiler. The display panel indicates the flow temperature s in central
With the boiler in rest, the diverter valve is in the domestic hot water position, activation of the central heating changes the
position of the motorised valve head, moving the diverter valve into the central heating position.
The start of the pump is delayed for 7 seconds to allow the movement of the diverter valve. The PCB checks the pressure of the
primary circuit, if the pressure measured is 0.8 bar or lower, the boiler will lockout after 40 seconds. The error code E02 will
appear on the LCD and the pump will stop.
If the pressure measured is above 0.8 bar, the boiler ignition sequence will begin.
At first, the fan starts and the speed increases to the required ignition speed (3460 rpm), once this speed has been achieved, the
safety coil of the gas valve is supplied with 230V DC, after 8 seconds the boiler checks that the burner has lit, if the boiler does
not sense that the burner has lit, the error code E04 will appear on the display, should this error occur, the boiler will attempt to
relight two more times (20 seconds between each attempt). After this, should the boiler still not sense a flame, error code A03 will
appear on the LCD. Should the boiler detect that the burner has lit, the boiler continues to regulate as follows.
The NTC fitted on the outlet of the primary circuit exchanger is the only NTC to adjust the heat output of the boiler according to
the adjustable setting point. This point is adjustable from 25°C to 85°C by the user. This NTC relays information to the PCB,
which in turn modulates the burner by adjusting the speed of the fan.
When the NTC senses that the set temperature has been achieved (+ 4°C to the temperature set by the user), the burner will go
out. To avoid excessive burner lighting, an anti-cycle timer can be set between 0 to 7 minutes in menu 4 line 48 (see Section 17
Adjustments and Settings).
The speed of the pump can be set at two levels. The PCB controls the speed of the circulation pump depending on the speed set
in menu 4 line 41. Setting 410 will cause the pump to operate continually at high speed, and setting 411 will cause the pump to
modulate between high and low speed depending on the ∆T between the inlet and the outlet. If the ∆T is greater than 20°C the
pump will run on high speed and if the ∆T is less than 20°C the pump will run on low speed.
N : T
OTE HE DEFAULT SETTING FOR THE PUMP IS HIGH SPEED
heating as illustrated below:
.
Central heating
mode ON
Room thermostat
contact ON
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