51
5. SEQUENCE OF OPERATION
Activation of the time clock and/or room thermostat starts the boiler.
The letter
C
is shown in the display followed by the flow
temperature.
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 star t of the pump is delayed for 7 seconds to allow the
movement of the diverter valve (when the pump starts it at speed 2).
There then follows a temperature and flow rate check on the flow
NTC (NTC1) and the return NTC (NTC2). The electronics check
NTC’s 1 and 2 for the correct
D
T (difference in temperature). The
D
T must be less than 5
o
C. If this is not correct after 40 seconds,
error code
E95
is shown but the pump continues to run. When the
check is correct the boiler automatically starts the sequence.
Following the satisfaction of the temperature/NTC check the fan
starts and an ignition attempt is then made for 3 seconds after the
fan starts. The gas valve is energised and gas is delivered to the
burner fixed in relation the the fan. The ignition gas pressure (soft
light) is adjusted at Step 1 in the parameter adjustment mode (see
Section 3.6.1). This value is factory set. (1= minimum fan speed and
00 = maximum fan speed). Soft light takes 4 seconds, the
electronics check for flame ionisation during this time. Failure on
ignition results in the error code
A01
.
For 12 seconds following the gas valve being energised, the ignition
is checked and the temperature and flow through the boiler is
monitored by the electronics. The
D
T must increase by more than
50
o
C. To check the correct temperature and flow the boiler remains
at a fixed output for 5 seconds, this value is 50 and can be viewed at
Step 6 (Section 3.6.1.) Incorrect readings will result in the error code
A02
being displayed and the pump stopping.
Following all checks the boiler is free to modulate the central heating
output. The maximum heat output is set at Step 2 (see Section
3.6.1) and is adjustable between 1 and 00 (minimum and maximum
output). The burner can activate up to a maximum of the set point at
+4
o
C. reignition of the burner occurs once it has thermostatically
turned off can be time delayed between 0 and 7 minutes, adjustable
in Step 3 (Section 3.6.1), the factory setting is 2 minutes.
After correct operation is proven the pump speed changes to speed
3 (if the system is cold), if the system is warm the pump remains at
speed 2.
In the event of overheating the display will show
A03
.
5.1
C
ENTRAL
H
EATING MODE
5.2
D
OMESTIC
H
OT
W
ATER
M
ODE
When a hot water tap is turned on the domestic hot water flow
switch is operated (if the diverter valve is in the central heating
position it will motor into the domestic hot water position and the
boiler starts. The letter
dd
is shown in the display followed by the
temperature of the domestic hot water leaving the appliance.
The appliance will then follow the same operating logic as described
in Central Heating Mode.
In domestic hot water mode NTC1 limits the maximum temperature
to 78
o
C, reignition will occur at 74
o
C. The domestic hot water
temperature is limited to 61
o
C, reignition will occur at 60
o
C.
Summary of Contents for ACO 27 MFFI
Page 49: ...49 WIRING DIAGRAM FOR CONNECTION TO AN ARISTON UNVENTED CYLINDER DIAGRAM A ...
Page 50: ...50 WIRING DIAGRAM FOR CONNECTION TO AN OPEN VENTED CYLINDER DIAGRAM B ...
Page 57: ...57 FIG 7 19 FIG 7 20 FIG 7 21 FIG 7 22 FIG 7 23 FIG 7 24 O P FIG 7 18 ...
Page 69: ...69 Model 27 32 RFFI SYSTEM ...
Page 70: ...70 ...
Page 71: ...71 ...
Page 77: ...77 ...
Page 78: ...78 11 BENCHMARK COMMISSIONING CHECKLIST ...
Page 79: ...79 12 SERVICE INTERVAL RECORD ...
