Ariston EURO COMBI A/27 MFFI User guide

A/23 MFFI - A/27 MFFI
G.C.N. 47-116-10 / 47-116-12
Servicing Instructions
Type C Boilers
LEAVE THESE INSTRUCTIONS
ADJACENT TO THE GAS METER

2
B029
Page No.
1. SERVICING INSTRUCTIONS
1.1 Replacement of Parts 3
1.2 To Gain General Access
- Removing the Front Panel 3
- Removing the Side Panels 4
- To Lower the Control Panel 4
1.3 Access to the Combustion Chamber
- Removing the Sealed Combustion Chamber 5
- Removing the Burner and Injectors 5
- Removing the Electrodes 6
- Removing the Main Heat Exchanger 7
- Removing the Air Pressure Switch 7
- Removing the Venturi Device 8
- Removing the Fan 8
1.4 Servicing and Removal of the Gas Valve
- Setting Gas Pressure 9
- Removing the Spark Ignitor 11
- Removing the Gas Valve 12
1.5 Access to the Hydraulic Circuit
- Removing the D.H.W. (Secondary) Exchanger 12
- Removing the Safety Valve 13
- Removing the Automatic Air Vent 13
- Removing the Main Flow Circuit Switch 13
- Removing the Pump 14
- Removing the Pressure Gauge 14
- Removing the Expansion Vessel 15
- Removing the Overheat Thermostat 15
- Removing the Heating Temperature Sensor (N.T.C.) 15
1.6 Access to the Control System
- Checking the Fuses 16
- Removing the Time Clock 16
- Removing the P.C.B.s 17
2. FAULT FINDING
2.1 Fault Finding Guide (Flow-chart) 18
2.2 Fault Finding Using the Total Check System 23
3. ELECTRICAL DIAGRAMS
3.1 Electrical Connection 24
3.2 Functional Flow Connection 25
4. SHORT SPARE PARTS LIST 26
TABLE OF CONTENTS

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B029
1. SERVICING
INSTRUCTIONS
The life of individual components vary and they will need servicing or
replacing as and when faults develop.
The fault finding sequence chart in chapter 2 will help to locate which
component is the cause of any malfunction, and instructions for removal,
inspection and replacement of the individual parts are given in the following
pages.
1.1 Replacement
of Parts
1.2 To Gain General
Access
All testing and maintenance operations on the boiler require the control panel
to be lowered.This will also require the removal of the casing.
To dismantle the front part of the casing, proceed as follows:
1. Remove screw “A” (see fig. 1.1) ;
2. Lift the front panel up and forward (see fig. 1.2) .
A
Fig. 1.2
Fig. 1.1
To ensure efficient safe operation, it is recommended that the boiler is
serviced annually by a competent person.
Before starting any servicing work, ensure both the gas and electrical
supplies to the boiler are isolated and the boiler is cool.
Before and after servicing, a combustion analysis should be made via the flue
sampling point (please refer to the Installation Manual for further details).
After servicing, preliminary electrical system checks must be carried out to
ensure electrical safety (i.e. polarity, earth continuity, resistance to earth and
short circuit).

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B029
Removing the side panels
1. Remove the screws “B”;
2. Pull the panel away from the boiler, then lift the panel
up and away from the boiler (see fig. 1.2).
To lower control panel
1. Remove the screws “B”
2. Push the two side panels outward slightly (fig. 1.5) ;
3. Rotate the control panel forward and down.
Fig. 1.4
B
Fig. 1.5
B
C
Fig. 1.7
Fig. 1.6
C
To access the areas where the adjustment and control devices are located,
simply remove the plugs by pressing from the inside, unscrew the screws “C”
and remove the bottom part of the instrument panel, rotating it upwards.
Fig. 1.3
B

1. Remove the side panels of sealed chamber (fig. 1.10) ;
2. Remove the screws “F” of the burner (see fig. 1.11) ;
3. Remove the burner (see fig. 1.12) ;
4. Remove the injectors using a No. 7 socket spanner;
5. Replace in reverse order.
Removing the burner and the
injectors
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B029
Removing the sealed chamber
frontal cover
1.3 Access to the
Combustion Chamber
Remove the screws “D”
Remove the screws “E”
Removing the combustion cover
EEE
EE
EE
Fig. 1.8 Fig. 1.9
DD
D
D
Fig. 1.10
Fig. 1.11
Fig. 1.12
F
push
push

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B029
Removing the electrodes 1. Remove rubber gasket “G” (see fig. 1.13) ;
2. Disconnect ignition leads by pulling downward (see fig. 1.14) ;
3. To remove the flame sensor, disconnect the cable at its only connection
point close to the P.C.B. (see fig. 1.15) ;
5. Remove screw “H” using a Philips No.2 star tip screwdriver (see fig. 1.16) ;
6. Slide the electrode gently downward (see fig. 1.17).
To replace, repeat the steps in reverse order, paying particular attention to the
following:
a -Centre the electrode in the positioning hole carefully, otherwise the
electrode may break;
b -Check that the cables have been connected correctly;
c -Check that the rubber gasket covers the cable/electrode connection
point completely.
Fig. 1.13
G
Fig. 1.14
Fig. 1.15
Fig. 1.16 Fig. 1.17
H

1. Disconnect the electrical connections “K” and silicone pipes “L” from their
connection points (see fig. 1.20) ;
2. Remove screws “J” on the top of the sealed chamber (see fig. 1.21) ;
Use a No. 2 star tip screwdriver to remove the switch from the plate.
Fig. 1.21
Fig. 1.20
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B029
1. Drain the boiler of water;
2. Release the two connection nuts “I” connecting the exchanger to the flow
and return pipes (see fig. 1.18) ;
3. Pull it straight out (see fig. 1.19).
Removing the main heat
exchanger
Removing the air pressure switch
Fig. 1.18
I
Fig. 1.19
L
L
K
JJ

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B029
1. Disconnect the silicone pipes “M” and remove the screw “N”
(see fig. 1.22) ;
2. Extract the venturi (see fig. 1.23) .
Removing the venturi device
1. Disconnect electrical connections and remove screws
“O” using a No. 2 star tipped screwdriver (see fig.1.24) ;
2. Pull fan to the right, forward and remove ( see fig.1.25) ;
3. Remove fan from mounting plate;
4. Remove screws “P” (see fig.1.26) .
Removing the fan
MN
Fig. 1.22 Fig. 1.23
Fig. 1.24
Fig. 1.25 Fig. 1.26
O
O
P
P

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B029
1.4 Servicing and Removal
of the Gas Valve
1
2
3
4
A
B
C
E
F
D
SIT
TANDEM
SIT
SIGMA 1
2
3
4
A
B
C
E
F
D

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B029
Setting the minimum and the maximum power of the boiler
1. Check that the supply pressure to the gas valve is a minimum of 20 mbar
for natural gas.
2. To do this, remove the screw “A”.
Fit the pipe of the pressure gauge to the pressure connection of the gas
valve “B”.
When you have completed this operation, replace the screw “A” securely
into its housing to seal off the gas.
3. To check the pressure supplied by the gas valve to the burner, remove the
screw “C”. Fit the pipe of the pressure gauge to the pressure outlet of the
gas valve “D”.
Disconnect the compensation pipe either from the gas valve or from the
sealed chamber.
4. Set the On/Off button to position < I > and the "summer/winter" switch to
the winter position.
To set the maximum power, turn on the hot water tap and allow the hot
water tap to run at a rate of about 8 litres/minute so that the main burner
lights.
Adjust nut “E” on the modureg to set the gas pressure (displayed on the
pressure gauge) corresponding to the maximum power (see table“A” page 11).
5. To set the minimum power, disconnect a supply terminal from the modureg
and adjust screw “F”.
Turn the screw clockwise to increase the pressure and coun-
ter-clockwise to decrease the pressure (displayed on the
pressure gauge) corresponding to the minimum power (see table “A” page
11).
6. When you have completed the above operations, turn off the
hot water tap, re-connect the supply terminal to the modureg
on the gas valve and replace the cap on the screw of the
modureg.
Setting the maximum heating circuit power
7. To set the maximum heating circuit power, place the
On/Off button to position < I > and the "summer/winter" switch to winter
position.
Turn the knob of the heating thermostat clockwise to maximum;
8. Remove the left hand inspection panel of the P.C.B. and fit a small
cross-head screwdriver in to the right hand potentiometer. Turn clockwise
to increase the pressure or counter-clockwise to reduce the pressure.
Adjust the setting to the required heating pressure value (displayed on the
pressure gauge), as indicated in the diagrams shown in page 11.
9. Turn off the boiler by placing the main switch to the "Off" position.
Setting pressure for soft ignition.
Disconnect the detection electrode connection from the P.C.B. (see fig.
1.13).
Start the boiler and during the ignition sequence adjust the centre
potentiometer until the gas pressure reads the required gas pressure as
per the table below.
Once the gas pressure is set turn off the boiler and reconnect the
connection to the P.C.B.
NB.:It may be necessary to reset the flame failure reset a number of times
during this operation.
Recommended pressure for
slow ignition 5 mbar - 1.95 in w.g.
NATURAL GAS (G20) BUTANE GAS (G30) PROPANE GAS (G31)
18 mbar - 7.0 in w.g. 19 mbar - 7.4 in w.g.
Setting gas pressures

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B029
model 23
model 27
Regulating the heating power for
natural gas (G20)
model 23
model 27
Regulating the heating power for
butane gas (G30)
model 23
model 27
34
36
38
40
Regulating the heating power for
propane gas (G31)
GAS REQUIREMENTS
Burner pressure
Burner injectors
min
13 x 1.25
Gas rate max 3.0 m 106.0 ft
Gas rate min 1.2 m
3/h
3/h 42.3 ft
3/h
3/h
Inlet pressure 20 mbar 7.8 in w.g.
Burner pressure max 12.3 mbar 4.8 in w.g.
2.0 mbar 0.8 in w.g.
13 x 0.72
0.88 m 31.1 ft
0.35 m
3/h
3/h 12.3 ft
3/h
3/h
28 mbar 10.9 in w.g.
28 mbar 10.9 in w.g.
5.1 mbar 2.0 in w.g.
13 x 0.72
1.15 m3/h 40.6 ft3/h
0.46 m3/h 16.2 ft3/h
37 mbar 14.4 in w.g.
37 mbar 14.4 in w .g.
7.0 mbar 2.7 in w.g.
NATURAL GAS (G20) BUTANE GAS (G30) PROPANE GAS (G31)
TABLE “A”

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B029
10. Remove the pipe from the pressure gauge and connect screw “C” to the
pressure outlet in order to seal off the gas.
11.Carefully check the pressure outlets for gas leaks (valve inlet
and outlet).
IMPORTANT!
Whenever you disassemble and reassemble the gas connections, always
check for leaks using a soap and water solution.
Setting the anti-cycling device
This appliance is equipped with a potentiometer which delays the ignition of
the heating control and is situated on the P.C.B.(see the electrical diagrams).
By adjusting the potentiometer, it is possible to change the time interval
between the burner shutting down and its next ignition.
It is preset at 1 minute and can be adjusted from 0 to 2 minutes.
Use this control in particular situations where continuous shutting down and
ignition of the main burner occurs.
40 50 60 70 80
C C
Anti-cycling
Device Soft-light
Adjustment Max. Heating Adjustment
Removing the spark generator (SIT Sigma gas valve)
1. Disconnect ignition leads “Q” by pulling upwards
(see fig. 1.27) ;
2. Remove the screws “R” (see fig. 1.28) with a Pozidrive
No. 2 star tip screwdriver;
3. Remove the spark generator.
Fig. 1.27
Fig. 1.28 Fig. 1.29
Q
R

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B029
Removing the spark generator (SIT Tandem gas
valve)
1.
Disconnect ignition leads “Q1” by pulling upwards
(see fig. 1.30) ;
2. Remove the screws“R1” (see fig.1.31) with a Pozidrive
No. 2 star tip screwdriver;
3. Remove the spark generator.
Fig. 1.30
Fig. 1.31 Fig. 1.32
Q1
R1
R1

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B029
1.5 Access to the
Hydraulic Circuits
Fig. 1.37
U
U
Removing the D.H.W. (secondary)
exchanger
1. Remove the screw “U” (see fig. 1.37) ;
2. Push the exchanger towards the rear of the
boiler, lift upwards and remove out of the
front of the boiler;
3. Before replacing the exchanger ensure that
the O-rings are in good condition and
replace if necessary.
Important! Before any component is removed, the boiler
must be drained of all water.
Removing the gas valve
1. Disconnect all the cables from the solenoid and
modureg;
2. Remove the spark generator;
3. Release the top nut “S” using a 30 mm open ended
spanner (see fig. 1.31) ;
4. Remove the screws “T” from the bottom of the gas
valve pipe (see fig. 1.32) .
Attention!! The gas valve is connected with the two pipes
(as shown) with an O-ring connection.
Fig. 1.33 Fig. 1.34
Fig. 1.35
S
T
T
Fig. 1.36

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B029
Removing the safety valve
1.
Loosen nut “V” (see fig. 1.38);
2. Remove the valve.
Removing the automatic air vent
1. Unscrew valve “W” (see fig. 1.39) .
Removing the main circuit flow
switch
1. Remove the cable of the main circuit flow switch “Y”;
2. Remove the screws “Y1” (see fig. 1.40);
3. Remove the main circuit flow switch.
Fig. 1.38
Fig. 1.39
Fig. 1.40
V
W
Y
Y1
Y1

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B029
Removing the pump
1.
Unscrew “Z” and remove the electrical connection
(see fig. 1.41) ;
2. Release the nuts “A1” and remove the pump
(see fig. 1.42) .
Removing the pressure gauge
1. Remove the inspection panel
(see fig. 1.6 - 1.7) ;
2. Release coupling “A2” using a 14 mm open ended
spanner (see fig. 1.43) ;
3. Push the pressure gauge through the control panel
from the rear (see fig. 1.44) .
A1
A1
Z
A2
Fig. 1.41 Fig. 1.42
Fig. 1.43 Fig. 1.44

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B029
Removing the expansion vessel
1.
Remove nut “A3” away from the expansion vessel
(see fig. 1.45) ;
2. Remove nut “A4” (see fig. 1.46) ;
3. Remove expansion vessel (see fig. 1.47) .
Removing the overheat thermostat
1. Remove the electrical connection from the overheat
thermostat (see fig. 1.48) ;
2. Then remove the thermostat from the pipe by releasing
its securing clip.
Removing the heating temperature sensor (N.T.C.)
1. Remove the electrical connector by pulling off the
thermostat connections and unscrewing the sensor
probe with a 14 mm open ended spanner (see fig.
1.49) .
A3
A4
Fig. 1.45
Fig. 1.46
Fig. 1.48
Fig. 1.49
Fig. 1.47

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B029
Checking fuse
1.
Remove the inspection panel
(see fig. 1.6 - 1.7) ;
2. Remove fuse (see fig. 1.50) .
1.6 Access to the Control
System
Removing the time clock
1. Remove the inspection panel
(see fig. 1.6 - 1.7) ;
2. Remove electrical connection of the clock “A5”
(see fig. 1.51) ;
3. Unclip the clock from the panel and remove
(see fig. 1.52) .
Fig. 1.50
Fig. 1.51 Fig. 1.52
A5

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B029
Removing the P.C.B.s
1. Isolate electricity;
2. Remove the front cover of the boiler;
3. Remove the inspection panel (see fig. 1.6-1.7 );
5. Remove the mounting screws “A6’ (see fig. 1.53) ;
6. Disconnect the connection cable”A7” (see fig. 1.54) ;
7. To remove the 24V P.C.B.: remove the electrical plug
connectors and screws “A8” (see fig. 1.55) ;
8. To remove the 240V P.C.B.: remove the electrical plug
connectors and screws “A9” (see fig. 1.56) ;
9. Replace either P.C.B. in reverse order.
Fig. 1.53
Fig. 1.54 Fig. 1.55 Fig. 1.56
A6 A6
A6 A6
A7
A7 A8
A8 A9
A9
N.B.
It is possible to by-pass the time clock in the event of failure by simply
unplugging the electrical connection from the P.C.B.
(see fig. 1.48 ). This will
revert control of the central heating to the room stat connection on the reverse
of the control panel.

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B029
2. FAULT FINDING
1)Thereissufficient
waterinthesystem
2) The gas is turned on
3)Theelectricitytothe
boilerison
PreliminaryChecks
Makesurethat:
HAS
THE LIGHT fOR
THE POWER SUPPLY
COME ON?
SETTING
FOR THE OPERATING
MODE
ISHOT
WATERBEING
DEMANDED?
NO NO
WINTER
SUMMER
FUME DISCHARGE TEST
NO
YES
YES
YES
NO NO
YES
YES
1)Check the fuses
2)Check the power
supply cord, plug and
outlet
3)Check/replacethepower
supplyPCB
Press the
On / Off Button
FOR BOILERS
EQUIPPED WITH AN
ELECTRONICANT-FREEZE
SYSTEM:HASTHE SAFETYBEEN
TRIGGERED TO ACTIVATE
THE DEVICE?
(T sensor <5°C)
FOR BOILERS
EQUIPPED WITH AN
ELECTRONICANT-FREEZE
SYSTEM:HASTHE SAFETYBEEN
TRIGGERED TO ACTIVATE
THE DEVICE?
(T sensor <5°C)
DO THE
PROGRAMMING
TIMERAND/OREXTERNAL
THERMOSTATNEED
TO BE ACTIVATED
A
ISHOT
WATERBEING
DEMANDED?
It is possible to detect and correct any defect by using the standard fault
finding diagrams described in this chapter.
2.1 Fault Finding Guide
(Flow-chart)