Ariston A23 MFFI, A27 MFFI Servicing Instructions

A/23 MFFI - A/27 MFFI

G.C.N. 47-116-10 / 47-116-12
Servicing Instructions
Type C Boilers

LEA VE THESE INSTRUCTIONS
ADJACENT T O 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 Ther mostat 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

3

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 electr ical system checks must be carried out to
ensure electrical safety (i.e. polar ity, earth continuity, resistance to earth and
short circuit).

4

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

5

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

E

E

E

E

E

E

E

Fig. 1.8

Fig. 1.9

D

D

D

D

Fig. 1.10

Fig. 1.11

Fig. 1.12

F

push

push

6

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 , pa ying 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

7

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

J

J

8

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 remo ve (

see fig.1.25)

;

3.

Remove fan from mounting plate;

4.

Remove screws “P”

(see fig.1.26)

.

Removing the fan

M

N

Fig. 1.22

Fig. 1.23

Fig. 1.24

Fig. 1.25 Fig. 1.26

O

O

P

P

9

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

10

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. T o set the minim um pow er, disconnect a supply terminal from the modureg
and adjust screw “F”.
Turn the screw clockwise to increase the pressure and coun­ter-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 ther mostat 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.

Setting gas pressures

Recommended pressure for
slow ignition

NATURAL GAS (G20) BUTANE GAS (G30) PROPANE GAS (G31)

5 mbar - 1.95 in w.g.

18 mbar - 7.0 in w.g. 19 mbar - 7.4 in w.g.

11

B029

Regulating the heating power for

natural gas (G20)

Regulating the heating power for

butane gas (G30)

Regulating the heating power for

propane gas (G31)

T ABLE “A”

model 23
model 27

model 23
model 27

GAS REQUIREMENTS

Gas rate
Gas rate

Inlet pressure
Burner pressure
Burner pressure
Burner injectors

40
38
36
34

model 23
model 27

NATURAL GAS (G20) BUTANE GAS (G30) PROPANE GAS (G31)

max
min

3

/h

3.0 m 106.0 ft

3

/h 42.3 ft

1.2 m

3

3

/h

20 mbar 7.8 in w.g.
max 12.3 mbar 4.8 in w.g.
min

2.0 mbar 0.8 in w.g.

13 x 1.25

/h

3

0.88 m 31.1 ft

/h

3

0.35 m

/h 12.3 ft

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

3

/h

1.15 m3/h 40.6 ft3/h

3

/h

0.46 m3/h 16.2 ft3/h
37 mbar

37 mbar 14.4 in w .g.

7.0 mbar 2.7 in w.g.

13 x 0.72

14.4 in w .g.

12

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

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

C C

13

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

14

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

15

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

16

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

17

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

18

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

19

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 rev erse
of the control panel.

20

B029

2. FAULT FINDING

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)

Preliminary Checks

Makesure that:

1) Thereis sufficient
water i nthesys tem

2) Thegas is turned on

3) Theelectr icitytothe

boiler is on

Press the

On /Off Button

HAS

THE LIGHT fOR

THE POWER SUPPLY

COME ON?

YES

NO

1)Checkthefuses

2)Check thepower
supply cord, plug and
outlet

3)Check/replacethepower
supply PCB

NO

SUMMER

ISHOT

WATERBEING

DEMANDED?

NO

FOR BOILERS

EQUIPPED WITHAN

ELEC T R ONICANT -FREEZE

SYST EM :HASTHESAFETYBEEN

TRIGGERED TO ACTIVATE

TH EDEVIC E?

(Tsensor <5°C)

SETTING

FOR THE OPERATING

MODE

FUME DISCHARGE TEST

YES

YES

A

YES

WIN TER

YES

ISHOT

WATERBEING

DEMANDED?

NO

DO THE

PROGRAMMING

TIMERAND/OREXTERNAL

TH ERM OS T ATNEED

TO BE ACTIVATED

NO

FOR BOILERS

EQUIPPED WITHAN

ELEC T R ONICANT -FREEZE

SYST EM :HASTHESAFETYBEEN

TRIGGERED TO ACTIVATE

TH EDEVIC E?

(Tsensor <5°C)

21

B029

A

DOES THE

CIRCULATIONPUMP

COME ON?

YES

NO

1)Checkfor air in the
system

2)Checkthepressureswitch
foractivatingpump

3)Check/replace water
gaug eandre fill the
thesyste mproperly

1)Turn the boiler off

and thenbackon
again (safe tyreset)

YES

DOES THE

INS UFFICI ENT WATER

INDIC ATORLIG H TCOME

ON?(wi thi n

40sec.)

NO

B

POWER TO
THE PUMP ?

YES

1)Check to see if pump is
stuck

2)Replacecirculationpump

NO

1) Check
wiring

2) Check/replace
wire toP CB

3) Replace
power supply
PCB

4) Replace control
PCB

5) Check micro­switch when hot
water isrequested.

22

B029

B

DOESTHE FAN

COME ON?

YES

C

NO

BOILER

SHUT D OWN ?

NO

PUMP

SAFETYDEVICE

ACTIVATED?

NO

INTERNAL

SAFETYDEVICE

FOR PCB

ACTIVATED?

NO

ISTHEREPOWER

TO THE FAN?

YES

YES

YES

YES

NO

1)Reset the boiler

1)Check/replacediffere ntial
pressureswitch for pump

2)Check/replace wiring

3)Check/replacePCB wire

4)Check/replace power
supply P CB

5)Check/replace control

PCB

1)

Check/replaceair

pressureswitch/wiring

2)Check whether reset
button isstuck

3)

Check/replace flame

dete cti onele ctrod e

1)

Check/replace wiring

2)

Check/replacePCB wire

3)Check/replacepower
supply PCB

4)

Check/replace control

PCB

5)

Check/replace air

pressureswitch

1)Replacefan

23

B029

C

IS

THEAIR PRESSURE

SWITCH ACTIVATED?

YES

ARETHE

FUMES DISCHARGED

CORRECTLY?

YES

DOESTHE

BURN ERLIGH T ?

YES

SAFETY

SHUT D OWNOFTHE

BOILER ACTIVATED?

NO

NO

NO

NO

YES

1) Check flue discharge

2) Check venturi & small pipes

3) Check wire for air press.switch

4) Check/replace air press. switch

5) Check/replace PCB wire

6) Check/replace power PCB

7) Check/replace control PCB

1)Check/replaceigniterplugs

2)Check wiring

3)Check starter

4)Check small wire

5)Check power supply PCB

6)Checkcontrol P C B

1)Checksupplyofgasto gas
valve

2)Check power supply PCB

3)Checkcontrol P C B

4)Checkfunct i o na lityofthe
valve

1)Check whether flame

dete cti onele ctrodeis
hitbythefla me

2)Check theelectrode

3)Check thepowerPCB

4)Checkthecontrol PCB

D

NO

WASTHE

RESET SWITCH

PRESSED?

YES

Shutdown LEDoff

Res tartofthefan

24

B029

D

THERE STILL A

IS

PROBLEM?

YES

NO

FUNCTIONS

NORMALLY

LISTOFMALF UNCT ION S

De live ryofhot wate rfordomes ti cuse :

De live ryofhot wate rfordomes ti cuse :

1

whenthetapisturnedon,theburnergoe sout.

whenthetapisturnedon,theburnergoe sout.

2

De live ryofhot wate rfordomes ti cuse :

De live ryofhot wate rfordomes ti cuse :

theradia tore sareheatedin summe rmode.

theradia tore sareheatedin summe rmode.

De live ryofhot wate rfordomes ti cuse :

De live ryofhot wate rfordomes ti cuse :

3

watertempe ra tureisnot satis f actory .

watertempe ra tureisnot satis f actory .

4

De live ryofhot wate rfordomes ti cuse :

De live ryofhot wate rfordomes ti cuse :

noisyopera tion.

noisyopera tion.

POSSIBLE CAUSES

- Airinthese c ondaryexchange r

- Airinthese c ondaryexchange r

- Hot water pressureswitch isdefective

- Hot water pressureswitch isdefective

- 3-way valve isdefective

- 3-way valve isdefective

- 3-way valve isdefective

- 3-way valve isdefective

- Checkhe a t i ngsensor s

- Checkhe a t i ngsensor s

- Checkgasset t i ngsandregula t ion

- Checkgasset t i ngsandregula t ion

- Checkwaterflowra t e

- Checkwaterflowra t e

- Check exchanger for domes tichot water

- Check exchanger for domes tichot water

- Primaryexchanger isdefective

- Primaryexchanger isdefective

- Low waterpressurein heatingsys tem

- Low waterpressurein heatingsys tem

- Checkgasset t i ngsandregula t ion

- Checkgasset t i ngsandregula t ion

5

Drop/increasein pre ss urein primarycircuit.

Drop/increasein pre ss urein primarycircuit.

6

Repeatedshutdowns.

Repeatedshutdowns.

7

Safe ty therm os ta tistrigge re drepe a te d ly.

Safe ty therm os ta tistrigge re drepe a te d ly.

8

Whenthecold watertapisturne doff,the

Whenthecold watertapisturne doff,the

boiler comeson.

boiler comeson.

9

Tempe rature of radiatorsnot s atisfactory.

Tempe rature of radiatorsnot s atisfactory.

- Checkfor leaksin heatingcircuit

- Checkfor leaksin heatingcircuit

- Defe ctivewater supplyinlet valve

- Defe ctivewater supplyinlet valve

- Secondary exchanger isdefective

- Secondary exchanger isdefective

- Expansion vessal is empty

- Expansion vessal is empty

- Detection electrodes are defective

- Detection electrodes are defective

- Checkgasset t i ngsandregula t ion

- Checkgasset t i ngsandregula t ion

- Checkelectrical circuit for f lamedetection

- Checkelectrical circuit for f lamedetection

- F a ulty(contacts)ntcheating sensors-

- F a ulty(contacts)ntcheating sensors-

- Defective (poorlycalibrated)safety thermostat

- Defective (poorlycalibrated)safety thermostat

- Pres e nceofair in theprimary watercircuit

- Pres e nceofair in theprimary watercircuit

- Dropin pre ss urein thewater mains,resulting

- Dropin pre ss urein thewater mains,resulting

in waterhammering

in waterhammering

- Checkntcheati ng s ensor

- Checkntcheati ng s ensor

- Check by-pass

- Check by-pass

- Checkgasset t i ngsandregula t ion

- Checkgasset t i ngsandregula t ion

25

B029

Signalling

Boiler Off
Auto diagnostic state
Spark ignition state
Boiler functioning normally
Lockout
Boiler thermostat satisfied
Room thermostat/clock no demand or
selector in summer setting

Malfunction

Faulty ventilation system
Air pressure switch stuck in N.O. position
Faulty reset switch
Faulty main circuit flow switch

Faulty flame detection
Faulty overheat ther mostat
Faulty exhaust fumes sensor
Faulty heating sensor (N.T.C.)
Faulty D.H.W.sensor (N.T.C.)

A
b

C

d

E
F

G

I

m

1
2
3
4
5
6

2.2

Fault Finding Using the
Total Check System

Pump fed

Main flow switch closed

Air pressure switch N.O.

Flame detected

Water at required temperature

Room thermostat/clock no demand or
selector in summer setting

Auto diagnostics faulty

Heating temperature control

D.H.W. temperature control

Heating circuit efficiency control

D.H.W.exchanger efficiency control

26

B029

3. ELECTRICAL DIAGRAMS

Legend:

AT = High V oltage P.C.B .
BT = Low Voltage P.C .B .
B = Flame Failure L.E.D.
C = Insufficient Water Pressure L.E.D.
D = Water Temperature Indicator L.E.D.s
E = Overheat Thermostat Warning L.E.D.
F = System Reset Button
G = Selector Knob for Operating Mode
H = Domestic Hot Water Temp. Adjustment
I = Central Heating Temp.Adjustment
J = Wire Connector for Room Thermostat
K = Connector for Total Check System
M = Anti-cycling Device Adjustment for Heating
N = Soft-light Adjustment
O = Max Heating Temperature Adjustment
P = Time Clock Connection
Q = On/Off L.E.D.
R = On/Off Switch
S = Interface Wire for P.C.B.s
T = Relay Motorised Valve
U = Ignitor Relay
V = Gas Valv e Relay
W = Fan Relay
X = Circulation Pump Relay
Y = Selector TCS2
Aa = Adaptor (British Gas use only)

A01= Air Pressure Switch
A02= Fan
A03= Gas Valve
A04= Ignitor
A05= Motorised Valv e
A06= Circulation Pump
A07= Flame Detector
A08= Earth T erminal
A09= Flame Detection Circuit
A10= Flame Indicator L.E.D.
A11= Transformer
A12= Filter

B01= Over Heat Thermostat
B02= Room Thermostat
B03= Gas Valve Modulator
B05= Heating Sensor
B06= Pressure Switch for Heating Circuit
B07= Microswitch for Diverter Valve
B08= Time Clock

Colours

Gry = Grey
Rd = Red
Bl = Blue
Grn/Yll = Yellow/Green
Wh = White
Brn = Brown
Blk = Black
Wh/Rd = White/Red

27

B029

A/23 MFFI - A/27 MFFI

EX C-MI/FFI

8

28

B029

4. SHORT SPARE PARTS LIST

A/23 MFFI - A/27 MFFI (SIT Sigma Gas Valve)

2

72

1

2

3

4

5

4

6

7
8
9

10

11

12

13
14

11
15

87

73

74

4

4

7

88

89

86

90

91

94

92

93

75

63

79

81

84

87

85

86

90

92

96

68 60 57

67 59 5861

66 64676669706471

75

76

77

78

80

82

11

83

104

103
100

102

98

101

100

97

85

95

23

6365

62

75

125

121

120

105

106

108

99

124

123

122

119

126

107

82

118

109

111

110

117

112

4

301 4 302 301

116

115

114

113

49

52

45

45

41

39

4

4

56

55

54

53
52
51
50
49
48
47
46

45
44

43
42

41
29
40
39

38

34

17 18 19 2320 21 22 24 2625

16

102 16

364

361

362

27

28

343332 35

3631

37

29 30

363

321

17

371

372

373

374

375

311

22

A 23/27 MFFI

29

B029

573294
573520
997206
573224
569236
573340
573528
573727
573172
571649
997208
953730
952981
952610
572989
572990
573343
573314
571651
571652
570717
564254
569387
571449
571646
573295
573825
571807
573521
997150
997151
571965
574279
574232
574233
573441
569390
569560
569561
572271
572277
572343
572372
572749
572835
571993
571444
997029
571443
571442
571447
571446
571547
571772
571771
571770
573138
569281
569282

Key

no.

G.C. part

no.

ARISTON

Part No.

Description

1
11
14
17
18
19
23
24
25
28
32
45
46
47

57AB
57CD

58
61

72AB
72CD

75
84
85
87

89AB
89CD

90
92
96

98AB
98CD

100
101
102
108
112
116
118

119
120A
120B
120C
120D

121AB
121CD

301

311

321

361

362

363

364

371

372

373

374

375

381

382

379816

164 225

164 338
164 229

378 814

E03 818
E02 071

379 079
164 230

164 282

379 981
164 261
379 979
379 980
E02 026

E02 078

164 311

Expansion vessel
Gasket 3/4"

Overheat thermostat
Main flow Switch
Temp probe (C.H.W.)
Microswitch for 3-way/main flow group
Gasket 1/2"
Manual vent cock
Safety valve 3 bar 1/2"
Pressure gauge
Time clock
P.C.B. EX C-MI/FFI
P.C.B. EI A-MFFI
P.C.B. cable
Fan
Fan
Fan inlet gasket
Venturi (exhaust manifold/header)
Air pressure switch
Air pressure switch
Fastening spring
Automatic air release valve
Gasket 1"
O-ring
Secondary exchanger (plate-type) exchanger 23kW
Secondary exchanger (plate-type) exchanger 27kW
O-ring (secondary exchanger)
20-18 O-ring
Gasket 3/8"
Pump
Pump
O-ring (13)
Gasket
Gas valve (SIT Sigma)
Spark generator
Detection electrode
Gasket 1/4"
Ignition electrode (R.H.)
Ignition electrode (L.H.)
Main burner
Main burner
Main burner
Main burner
Main exchanger
Main exchanger
Front panel runner kit
D.H.W. actuator kit
SIT Sigma gas valve operator coils
Heating by-pass kit
D.H.W. pressure switch kit
3-way spring kit
D.H.W. diaphram valve
Main flow switch diaphram
Main flow switch magnet
Main flow switch spring
Main flow switch top cap
Main flow switch reed system
Burner jet 1.25 full kit (Natural gas)
Burner jet 0.72 full kit (LPG)

1
1

1
1
1

1
1
1
1
1
1
1
1
1
1
1
1
1

1
1

1
1

1
1
1

1
1
1
1
1
1
1
1
1
1
1
1

A/23 MFFI - A/27 MFFI (SIT Sigma Gas Valve)

30

B029

A/23 MFFI - A/27 MFFI (SIT Tandem Gas Valve)

Key

no.

1
11
14
17
18
19
23
24
25
28
31
44
46
47

57AB

57CD

58
61

72AB
72CD

75
84
85
87

89AB
89CD

90
92
96

98AB
98CD

101

103
106
114
118
120
121

122A
122B
122C
122D

123AB

123CD

311
321
322
323
361
362
363
364
371
372
373
374
375
381
382

G.C. part

no.

379816

164 225

164 338
164 229

378 814

E03 818
E02 071

379 079
164 230

164 282

379 976

379 981
164 261
379 979
379 980
E02 026

E02 078

378 978
378 815
164 303

164 311

Description

Expansion vessel
Gasket 3/4"
Overheat thermostat
Main flow Switch
Temp probe (C.H.W.)
Microswitch for 3-way/main flow group
Gasket 1/2"
Manual vent cock
Safety valve 3 bar 1/2"
Pressure gauge
Time clock
P.C.B. EX C-MI/FFI
P.C.B. EI A-MFFI
P.C.B. cable
Fan
Fan
Fan inlet gasket
Venturi (exhaust manifold/header)
Air pressure switch
Air pressure switch
Fastening spring
Automatic air release valve
Gasket 1"
O-ring
Secondary exchanger (plate-type) exchanger 23kW
Secondary exchanger (plate-type) exchanger 27kW
O-ring (secondary exchanger)
O-ring (20-18)
Gasket 3/8"
Pump
Pump
Gas valve (SIT Tandem)
Spark generator
O-ring (13)
Detection electrode
Gasket 1/4"
Ignition electrode (R.H.)
Ignition electrode (L.H.)
Main burner
Main burner
Main burner
Main burner
Main exchanger
Main exchanger
D.H.W. actuator kit
SIT Tandem gas valve operator coils
SIT Tandem modureg coil
Gas modulator cartridge
Heating by-pass kit
D.H.W. pressure switch kit
3-way spring kit
D.H.W. diaphram valve
Main flow switch diaphram
Main flow switch magnet
Main flow switch spring
Main flow switch top cap
Main flow switch reed system
Burner jet 1.25 full kit (Natural gas)
Burner jet 0.72 full kit (LPG)

ARISTON

Part No.

1
1

1
1
1

1
1
1
1
1
1
1
1
1
1
1
1
1

1
1

1
1

1
1
1

1
1
1
1
1
1
1
1
1
1
1
1

573294
573520
997206
573224
569236
573340
573528
573727
573172
571649
997207
953730
952981
952610
572989
572990
573343
573314
571651
571652
570717
564254
569387
571449
571646
573295
573825
571807
573521
997150
997151
570732
573023
571965
573441
569390
569560
569561
572271
572277
572343
572372
572749
572835
571444
570712
573740
573745
571443
571442
571447
571446
571547
571772
571771
571770
573138
569281
569282

31

B029

573294
573520
997206
573224
569236
573340
573528
573727
573172
571649
997207
953730
952981
952610
572989
572990
573343
573314
571651
571652
570717
564254
569387
571449
571646
573295
573825
571807
573521
997150
997151
570732
573023
571965
573441
569390
569560
569561
572271
572277
572343
572372
572749
572835
571444
570712
573740
573745
571443
571442
571447
571446
571547
571772
571771
571770
573138
569281
569282

Key

no.

G.C. part

no.

ARISTON

Part No.

Description

1
11
14
17
18
19
23
24
25
28
31
44
46
47

57AB
57CD

58
61

72AB
72CD

75
84
85
87

89AB
89CD

90
92
96

98AB
98CD

101
106

114
118
120

121
122A
122B
122C
122D

123AB

123CD

311

321

322

323

361

362

363

364

371

372

373

374

375

381

382

379816

164 225

164 338
164 229

378 814

E03 818
E02 071

379 079
164 230

164 282

379 976

379 981
164 261
379 979
379 980
E02 026

E02 078

378 978
378 815
164 303

164 311

Expansion vessel
Gasket 3/4"
Overheat thermostat
Main flow Switch
Temp probe (C.H.W.)
Microswitch for 3-way/main flow group
Gasket 1/2"
Manual vent cock
Safety valve 3 bar 1/2"
Pressure gauge
Time clock
P.C.B. EX C-MI/FFI
P.C.B. EI A-MFFI
P.C.B. cable
Fan
Fan
Fan inlet gasket
Venturi (exhaust manifold/header)
Air pressure switch
Air pressure switch
Fastening spring
Automatic air release valve
Gasket 1"
O-ring
Secondary exchanger (plate-type) exchanger 23kW
Secondary exchanger (plate-type) exchanger 27kW
O-ring (secondary exchanger)
O-ring (20-18)
Gasket 3/8"
Pump
Pump
Gas valve (SIT Tandem)
Spark generator
O-ring (13)
Detection electrode
Gasket 1/4"
Ignition electrode (R.H.)
Ignition electrode (L.H.)
Main burner
Main burner
Main burner
Main burner
Main exchanger
Main exchanger
D.H.W. actuator kit
SIT Tandem gas valve operator coils
SIT Tandem modureg coil
Gas modulator cartridge
Heating by-pass kit
D.H.W. pressure switch kit
3-way spring kit
D.H.W. diaphram valve
Main flow switch diaphram
Main flow switch magnet
Main flow switch spring
Main flow switch top cap
Main flow switch reed system
Burner jet 1.25 full kit (Natural gas)
Burner jet 0.72 full kit (LPG)

1
1

1
1
1

1
1
1
1
1
1
1
1
1
1
1
1
1

1
1

1
1

1
1
1

1
1
1
1
1
1
1
1
1
1
1
1

103

A 23/27 MFFI (SIT Tandem Gas Valve)

Manufacturer: Merloni TermoSanitari SpA - Italy
Commercial subsidiary: MTS (GB) LIMITED

MTS Building
Hughenden Avenue,
High Wycombe
Bucks HP13 5FT
Telephone: [phone] ­Fax:[phone]

Technical Service Hotline: [phone]

23 99 84 1268 000 - B029

Stampa BIEFFE Recanati