Biasi M110.24SM/E User manual

Wall hung, fan flue, room sealed, high efficiency gas boiler
Service manual
GARDA PLUS HE
Models: G.C. Appl. No.
M110.24SM/E 47---970---31
M110.32SM/E 47---970---32
Leave this manual adjacent to the gas meter

Ta b le o f c o n t e n t s
1 Overall information 1..................
1.1 Overall View 1.........................
1.2 Hydraulic diagram 1....................
2 General access and emptying
hydraulic circuits 2....................
2.1 Nomenclature 2........................
2.2 Body panels 2.........................
2.3 Control panel 2........................
2.4 Access to the sealed chamber 3.........
2.5 Emptying the primary circuit 3...........
2.6 Emptying the d.h.w. circuit 4............
3Diagrams 5...........................
3.1 Wiring diagram 5.......................
3.2 Circuit voltages 6......................
4Faultfinding 7........................
5 Condensing heat exchanger 9..........
5.1 Function 9.............................
5.2 Removal 9............................
5.3 Cleaning 10............................
6 D.h.w. heat exchanger 11...............
6.1 Function 11.............................
6.2 Removal 11............................
7Pump 12...............................
7.1 Function 12.............................
7.2 Checks 12.............................
7.3 Removal 12............................
8 Three way diverter valve 13.............
8.1 Function 13.............................
8.2 Checks 13.............................
8.3 Removal of the electric actuator 13........
8.4 Removal of the diverter group and its
internal parts 14.........................
9 Electronic control/ignition p.c.b. 15......
9.1 Function 15.............................
9.2 Selection and adjustment devices 15......
9.3 Checking the temperature 16.............
9.4 Operation lights 17......................
9.5 Setting the boiler control function modes 18
9.6 Adjustment of maximum useful output
in c.h. mode 18.........................
9.7 Reignition frequency setting 18...........
9.8 Checks 19.............................
9.9 Removal of the electronic control p.c.b 19..
9.10 Thermal control in the ” ”mode 21......
9.11 Thermal control in the ” ”mode 22......
10 Transformer 23.........................
10.1 Removal 23............................
10.2 Check the transformer 23................
11 Gas valve 24...........................
11.1 Function 24.............................
11.2 Description of the parts 24...............
11.3 Adjustment 24..........................
11.4 Checks 25.............................
11.5 Removal of the gas valve 25..............
12 Primary circuit flow switch 27...........
12.1 Function 27.............................
12.2 Checks 27.............................
12.3 Removal 27............................
13 Expansion vessel and
temperature -- pressure gauge 28........
13.1 Function 28.............................
13.2 Checks 28.............................
13.3 Removal of the expansion vessel 28.......
13.4 Removal of temperature---pressure gauge 28
14 D.h.w. flow switch, filter and flow limiter 29
14.1 Function 29.............................
14.2 Description and location of parts 29.......
14.3 Checks 29.............................
14.4 Removal of the flow switch sensor 29......
14.5 Removal of the flow switch group
and d.h.w. circuit filter 29.................
14.6 Flow limiter 30..........................
15 Temperature probe 31..................
15.1 Function 31.............................
15.2 Checks 31.............................
15.3 Removal of the c.h.Temperature probe 31..
15.4 Removal of the d.h.w.Temperature probe 31
16 By--pass valve 33......................
16.1 Function 33.............................
16.2 Removal 33............................
17 Fan and Air box 34.....................
17.1 Function 34.............................
17.2 Removal of the fan group 34..............
17.3 Removal of the Air box 35................
17.4 Removal of the Fan 35...................
18 Ignition and detection electrodes,
burner and spark generator 36..........
18.1 Function 36.............................
18.2 Removal of the Ignition and detection
electrodes 36...........................
18.3 Removal of the burner 36................
18.4 Removal of the front insulation panel 37....
18.5 Removal of the rear insulation 37..........
18.6 Removal of the flue hood 38..............
18.7 Removal of the spark generator 38........
18.8 Checks 38.............................
19 Safety thermostat 40...................
19.1 Function 40.............................
19.2 Checks 40.............................
19.3 Removal 40............................
20 Flue temperature probe NTC 41.........
20.1 Function 41.............................
20.2 Removal 41............................
20.3 Checks 41.............................
21 Condensate trap 42....................
21.1 Function 42.............................
21.2 Removal 42............................
22 External temperature probe (optional) 43
22.1 Function 43.............................
22.2 Checks 43.............................
23 Short spare parts list 44................

1
1Overall information
1.1 Overall View
Fan
Safety
thermostat
Burner
Ignition
electrodes
Gas valve
Control
panel
Automatic
air release
Pump
D.h.w. temp.
probe
D.h.w.
heat exchanger
Expansion
vessel
Detection
electrode
valve
Condensing
Diverter valve
Main circuit
Flue temperature
heat exchanger
Condensate
trap
flow switch
C.h. temp.
probe
probe NTC
Air
restrictor Gas restrictor
Transformer
Switch
D.h.w. Flow
Spark
Generator
s
1.2 Hydraulic diagram
Central heating (c.h.) operation Domestic hot water (d.h.w.) operation
C.h.
water flow
C.h.
water return D.h.w.
inlet D.h.w. outlet

2
2General access and emptying
hydraulic circuits
2.1 Nomenclature
2
6
1
54
3
Fig. 2.1
1 Right side panel
2 Front panel
3 Control panel lid
4 Control panel cover
5Servicepanel
6 Left side panel
2.2 Body panels
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
For the most part of the check and maintenance oper-
ations it is necessary to remove one or more panels of
the case.
Thesidepanelscanberemovedonlyaftertheremoval
of the front panel.
To remove the front panel remove screws A(Fig. 2.2),
lift the panel and remove it.
A
Fig. 2.2
To remove the side panels loosen the screws Band C
(Fig. 2.3), bring the base of the panels away from the
boiler and lift them, freeing them from the top hooks.
B
D
C
Fig. 2.3 --- bottom view of the boiler
2.3 Control panel
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
To gain access to the parts located inside the control
panel proceed as follows:
1 Remove the front panel of the case
2 Loosen the screws Band C(Fig. 2.3).
3RemovethescrewsD
4 Move the lower part of the side panels as indi-
cated in Fig. 2.4 and pull the control panel.
When completely pulled out, the panel can rotate
45˚downwards to facilitate the service oper-
ations on the internal parts.

General access and emptying hydraulic circuits
3
Fig. 2.4
5RemovethescrewsEand remove the service
panel (Fig. 2.5);
If the external temperature probe (optional) is fitted fol-
low the steps 6 to 9.
6RemovethescrewsFand remove external tem-
perature probe lid.
E
I
I
F
Fig. 2.5
7 With the help of a screwdriver disconnect the ter-
minal block G(Fig. 2.6).
8RemovetheclampHthat holds the cable.
GH
Fig. 2.6
9 Pass the terminal block connected to the boiler
through the hole of the control panel lid (Fig. 2.7).
Fig. 2.7
10 Remove the screws Iand remove the control pan-
el lid (Fig. 2.5);
2.4 Access to the sealed chamber
J
J
Fig. 2.8
To gain access to the parts contained in the sealed
chamber it is necessary to remove the lid of the sealed
chamber.
For this purpose, remove the front and side panels of
the case, remove the screws Jas indicated in Fig. 2.8
and remove the lid.
2.5 Emptying the primary circuit
1 Close the c.h. circuit flow and return cocks K.
(Fig. 2.9).

General access and emptying hydraulic circuits
4
K
K
N
Fig. 2.9 --- bottom view of the boiler
2 Remove the front and right panels of the boiler.
3 Open the drain tap L(Fig. 2.11) until the boiler is
completely emptied.
4 To help the draining of the primary circuit loose
the condensing heat exchanger air purger valve
M
M
Fig. 2.10
Attention: some water could remain in the condens-
ing heat exchanger.
5 Close drain tap once the emptying has been
completed.
L
Fig. 2.11
2.6 Emptying the d.h.w. circuit
6 Close the d.c.w. inlet cock N(Fig. 2.9);
7 Open one or more hot water taps until the boiler
has been completely emptied.

5
3Diagrams
3.1 Wiring diagram
M110.24SM/...M110.32SM/...
Ignition
electrodes
Flame detection
electrode
External controls
terminal block
Electric supply
terminal block
Three way
diverter valve
Pump
Fan
Primary circuit
flow switch
D.h.w. flow
switch
C.h. temperature
probe NTC
Gas valve
Safety
thermostat
Flue
temperature
D.h.w. temperature
probe NTC
probe NTC
LD1LD2LD3
F1
F2
F3
K1
K2
K3
K4
LD4
P6
T3
X1
X2
X3
X5
X6
X7
X10X11
X12
X13
X17
X23
X24
P3
X14
X15
SB1
X16
X22
X9
bu bn
bu
bn
bububnbn
123
LN
gnye bu bn
bnbkbu
bn bu
gnye
bn bk bu
bn
gnye bu
M
~
rd
bk
wh
3
2
1
gnye
bnbu rd wh bk bu bn
gnye
gnye
bu
bn
bu
gnye
1
3
4
bu bn
bn bu
rdwhog
gy
gy
t
t
bk rd
rd
bk
bu
bu
bu bu
rd
wh
bu
wh
bu
rd
M
~
rd
bk
bu
gy
wh
rd
gy
bu
wh
bk
t
bn
bu
wh
wh
whwh
bnbu
COM
NO
rd
rd
rd
rd
gy gy
gy
gy
Transformer
230V~ / 24V~
Spark
Generator
rd bk
rd bk
Time switch
rd
gn
bk
wh
bn = brown
bu = blue
bk = black
wh = white
rd = red
gy = grey
gn = green
ye = yellow
vt = violet
og = orange
gnye = green/yellow
External temperature probe
terminal block
gnye
rdwh = red/white
bn
whwh

Diagrams
6
3.2 Circuit voltages
Electrical voltages with burner on
during c.h. or d.h.w. operation
only during c.h. operation
only during d.h.w. operation
230~
Safety
thermostat
0
Fan
0
Main circuit
LD1LD2LD3
F1F2
F3
K1
K2
K3
K4
LD4
P6
T3
X1
X2
X3
X5
X6
X7
X10X11
X12
X13
X17
X23
X24
P3
X14
X15
SB1
X16
X22
X9
Supply network
230~
Pump
230~ 0230~0
3way
diverter valve
230~
Gas valve
24~
Transformer
24=
230~
0
5=
D.h.w.
Flow switch
pressure switch

7
4Fault finding
Components to check
Section of the manual ! (note ref. in brackets)
10 ---
(1)
---
(2)
---
(3)
21.1 ---
(4)
67.2 8.2 9.8 11.4 12.2 14.5 15.2 16 17 18.8 18.8 19.2 19.2 20.1 ---
(7)
--- ---
L o c k --- o u t s i g n a l la m p r e d
Defect #
Transformer
Power supply line
Gas supply line
Flue pipes
Condensate drain pipe and trap
C.h. circuit
D.h.w. circuit
D.h.w. heat exchanger
Pump
Diverter valve
D.h.w. flow switch
Fuses (Electronic p.c.b.)
Electronic p.c.b.
Boiler settings
Gas valve
Main circuit flow switch
D.h.w. filter
Main circuit temp. probe
D.h.w. temp. probe
B y --- p a s s v a l v e
Fan air restrictor
Spark generator
Ignition electrode
Detection electrode
Safety thermostat
Gas restrictor
Flue temperature probe NTC
Expansion vessel
Safety valve
Pressure gauge
By pressing the reset push---button the boiler turns on and operates cor- rectly.
J J J J J J J J J J
By pressing the reset push---button the boiler starts the ignition cycle. The burner doesn’t light on and the boiler locks again.
J J J J J J J J J J J
ON
By pressing the reset push---button the boiler starts the ignition cycle. The burner lights on and the boiler
locks again.
J J J J J
The boiler does not start either in c/h or d.h.w. mode. All the operation lights OFF Fan still.
J J J J
The burner doesn’t light either in c.h. or d.h.w. mode. Fan turns.
J J J J
The burner doesn’t light either in c.h. or d.h.w. mode. Fan doesn’t turn.
J J J J J
The boiler doesn’t control the d.h.w. temperature. Turning the d.h.w. temp. adjustment knob hasn’t effect on the modulation of the flame. The boiler operates correctly on c.h.
J J
OFF
The boiler lights for a short while on c.h. Normal operation on d.h.w. function.
J J J J J

8
Components to check
Section of the manual ! (note ref. in brackets)
---------
(7)
20.119.219.218.818.8171615.214.512.211.49.88.27.26---
(4)
21.1---
(3)
---
(2)
---
(1)
10
L o c k --- o u t s i g n a l la m p r e d
Pressure gauge
Safety valve
Expansion vessel
Flue temperature probe NTC
Gas restrictor
Safety thermostat
Detection electrode
Ignition electrode
Spark generator
Fan air restrictor
B y --- p a s s v a l v e
D.h.w. temp. probe
Main circuit temp. probe
D.h.w. filter
Main circuit flow switch
Gas valve
Boiler settings
Electronic p.c.b.
Fuses (Electronic p.c.b.)
D.h.w. flow switch
Diverter valve
Pump
D.h.w. heat exchanger
D.h.w. circuit
C.h. circuit
Condensate drain pipe and trap
Flue pipes
Gas supply line
Power supply line
Transformer
Defect #
The boiler does not supply d.h.w. (cold water from the tap). Regular operation in c/h mode even during a drawing off d.h.w.
J J J
On c/h mode the temperature of the main circuit reaches 90°Candthec/h
system does not heat. The boiler operates correctly on d.h.w. mode.
J J J
Incorrect modulation J J J J Noisy bolier J J J J J J Poor c.h. / d.h.w. temperature (9) J J J J J
F
Poor d.h.w. temperature. Regular operationinc/hmode.
J J J
(8)
J
OF
F
Low d.h.w. flow rate J J J
---
Water leaks from the safety valve dur- ing operation on c/h
J J J J J
---
Water leaks from the safety valve when the boiler is off.
J J
Note Useful information can be obtained also from the optical indication given by the appliance oper- ation lights (see section 9.4). 1 Check for 230V~ between line (L) and neutral (N)
Verify the integrity of supply cable, plug and external fuses. Check the polarity of line and neutral connection
2 Verify the soundness of the gas supply pipe, the position of
stop valves.
3 Check for soundness and absence of obstructions. Verify that
the flue terminal is correctly installed (see clearances) and en- sure that exhaust gas is not sucked back by the boiler.
4 Check for soundness of the circuit and verify its correct filling
(see also installation manual).
5 A j a m m e d b y --- p a s s c o u l d c a u s e t h e o v e r --- h e a t i n g o f t h e m a i n
circuit and the intervention of the safety thermostat.
6 Using the flue analyzer, check the CO2value of the flue gases.
This reading is a reference value for the gas valve setting.
7 Check the pressurization of the expansion vessel. Refer to the
installation manual for proper values.
8 d.h.w. pressure too high or flow rate too high. If necessary in-
sert a flow rate limiter (14.6).
9 The boiler doesn’t reach the nominal heat input.

9
5Condensing heat exchanger
5.1 Function
The Condensing heat exchanger Ain Fig. 5.1 has the
function of transferring heat produced from combus-
tion of the gas and from the flue exhausted gas to the
water circulating in it.
A
B
C
Fig. 5.1
By reducing the combustion products temperature, the
latent heat of the vapour is transferred to the water cir-
cuit, allowing an extra gain of useful heat.
The condensed vapour is then drained through the
condensate trap Band the draining pipe C.
5.2 Removal
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1 Disconnect the flue system from the boiler.
2 Remove the air box following the instructions
from 1 to 7 in section 17.2
3 Disconnect the detection electrode connector D,
the ignition electrodes connector Eand the earth
wire F.
4 Disconnect the fan connector Gby pressing the
plastic hook placed on the rear side of the con-
nector (Fig. 5.3).
5 Unscrew the nuts H(Fig. 5.2).
6 Remove the fan---burner group I.
7 Empty the primary circuit of the boiler.
D
E
F
H
I
Fig. 5.2
G
Fig. 5.3
8 Disconnect the C.h. temperature probe Jand the
flue temperature probe connector K(Fig. 5.4).

Condensing heat exchanger
10
J
K
S
L
M
Fig. 5.4
9 Using pliers, remove the spring Lmoving it down-
wards and disconnect the rubber pipe M
(Fig. 5.4).
10 Remove the clips N(Fig. 5.6).
11 Completely loosen the connection Oand slightly
move the pipe Pupwards, then turn it towards
right (Fig. 5.5)
12 Completely loosen the connection Qand move
the pipe Rdownwards (Fig. 5.5).
P
R
O
Q
Fig. 5.5
13 Free the pipes R and P from the connection of the
Condensing heat exchanger (Fig. 5.6).
N
P
R
U
T
T
Fig. 5.6
14 Unscrew the screws Sand remove the clamps
(Fig. 5.4).
15 Unscrew the screws Tand remove the support
U(Fig. 5.6).
16 Remove the Condensing heat exchanger by
levering it and sliding it forwards.
17 Reassemble the Condensing heat exchanger
carrying out the removal operations in reverse
order.
5.3 Cleaning
If there are deposits of dirt on the coil of the Condensing
heat exchanger, clean with a bristle paintbrush and re-
move the dust with a hoover.
Warning: After cleaning or replacement as
detailed above, if it deemed necessary to
undertake a combustion analysis, refer to
the appropriate chapter Maintenance of the
installation instructions manual.

11
6D.h.w. heat exchanger
6.1 Function
The d.h.w heat exchanger Ain Fig. 6.1 and Fig. 6.3 al-
lows the instantaneous transfer of heat from the primary
hydraulic circuit to the water destined for d.h.w use.
A
Fig. 6.1
The schematic structure is shown in Fig. 6.2.
Primary hydraulic circuit
Domestic hot water circuit
Fig. 6.2
6.2 Removal
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1 Remove the front and right hand side panels of
the case.
2 Empty the primary circuit and the d.h.w circuit of
the boiler.
3 Completely unscrew the two Allen key screws B
(Fig. 6.3) which hold the exchanger to the brass
groups.
B
A
Fig. 6.3
4 Move the exchanger towards the rear of the boiler
and extract it.
Reassemble the d.h.w. heat exchanger carrying out the
removal operations in the reverse order.
Attention. When reassembling the exchanger be
sure to put the off centre location/securing pin indi-
cated in Fig. 6.4 towards the left side of the boiler.
Fig. 6.4

12
7Pump
7.1 Function
The pump Ain Fig. 7.1 and Fig. 7.2 has the function of
making the water in the main circuit circulate through
the main condensing heat exchanger and therefore
through the c.h. system (during the c.h. function) or
through the secondary heat exchanger (during the
d.h.w. function).
A
Fig. 7.1
7.2 Checks
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
nCheck that the pump is not seized and that the
movement of the rotor is not subject to mechanical im-
pediments.
With the boiler off, remove the front panel. Remove the
air release plug of the pump and turn the rotor with a
screwdriver.
nCheck the electrical continuity.
With the boiler off, remove the front panel and discon-
nect the connector B(Fig. 7.3).
Measure the electrical resistance between the pump
supply connections.
Electrical resistance of the windings (at ambient tem-
perature) must be about 230 Ω
nCheck the absence of starting defects.
With the boiler off remove the front case panel.
Remove the air release plug from the pump. Start the
boiler and with a screwdriver, turn the rotor in the direc-
tion of the arrow. If there is a defect in starting, the rotor
will begin to turn normally only starting it manually.
nCheck that the impeller is integral with the rotor.
With the boiler off remove the front and right hand side
case panels, lower the control panel and empty the pri-
mary circuit.
Remove the pump head by undoing the screws which
hold it to the pump body and check that the impeller is
firmly joined to the rotor.
7.3 Removal
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1 Remove the front and right hand side case panels
2 Empty the primary circuit of the boiler.
3 Extract and lower the control panel.
4 Disconnect the connector B (Fig. 7.2).
5 Loosen the connection C,removetheforkDand
the pipe E.
B
C
D
E
A
Fig. 7.2
6RemovetheforkF(Fig. 7.3) and the connection
of the capillary pipe of the pressure gauge.
7 Remove the locking plate G
8 Completely loosen the connection H.
9 Unscrew the two screws Ithat hold the pump on
theframeandremovethepump.
FG H
Fig. 7.3
Reassemble the pump carrying out the removal oper-
ations in the reverse order. When reassembling the
pump, check the correct location of the O---ring gasket
in the inlet port of the pump that seals the connection
between the pump and the brass group.

13
8Three way diverter valve
8.1 Function
The diverter valve A(Fig. 8.1) has the function of mod-
ifying the hydraulic circuit of the boiler by means of an
electric command given by the electronic control p.c.b.
in order to send the water that exits the primary heat ex-
changer towards the c.h. system or towards the d.h.w.
heat exchanger.
A
Fig. 8.1
8.2 Checks
nCheck the electrical continuity
Fig. 8.2 indicates the relationship between the electric
command coming from the electronic control p.c.b.
and the position of the actuator B(brass spindle) when
the boiler operates in d.h.w. mode.
Fig. 8.3 indicates the relationship between the electric
command coming from the electronic control p.c.b.
and the position of the actuator B(brass spindle) when
the boiler operates in c.h. mode.
In both figures the relationship between the position of
the actuator and the resistance of the motor windings
(the motor must be disconnected from the wiring) is
also given.
B
rd = red
bk = black
wh = white
0V
230 V
Spindle B
not visible
Open circuit
9,4 Kohm
wh
rd
bk
3
1
2
F i g . 8 . 2 --- D. h . w. m o d e
B
230 V
0V
Spindle B
visible
Open circuit
9,4 Kohm
wh
rd
bk
3
1
2
rd = red
bk = black
wh = white
F i g . 8 . 3 --- C . h . m o d e
8.3 Removal of the electric actuator
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1 Remove the front case panel.
2 Disconnect the connectors C(Fig. 8.4).
3 Remove the fixing spring Dand remove the
actuator E.
Reassemble the actuator carrying out the re-
moval operations in the reverse order.
When reassembling the actuator, refer to Fig. 8.2
or to the wiring diagram in section NO TAG for the
correct wiring connection.

Three way diverter valve
14
CDE
Fig. 8.4
8.4 Removal of the diverter group and its
internal parts
1 Remove the front and both side case panels.
2 Empty the primary circuit and the d.h.w circuit of
the boiler.
3 Remove the electric actuator (see section 8.3).
4 Remove the fixing spring F(Fig. 8.5) and remove
the primary circuit flow switch G.
5 Disconnect d.h.w. temperature probe H.
6 Unscrew the connector I, the c.h. flow connector
and the d.h.w. outlet connector.
FG
I
H
Fig. 8.5
7 Remove the d.h.w. heat exchanger (see section
6.2).
8RemovetheforkJand move away the pipe K
(Fig. 8.6).
9 Unscrew the screw Land remove the diverter
group.
J
K
L
Fig. 8.6 Rear view of the boiler
10 Refer to the exploded view in Fig. 8.7 to remove
the internal parts of the three way diverter valve.
Fig. 8.7
11 Reassemble the diverter group carrying out the
removal operations in the reverse order.

15
9Electronic control/ignition p.c.b.
9.1 Function
From other boiler devices....
C.h. temperature probe NTC
D.h.w. temperature probe NTC
D.h.w. flow switch
Primary circuit flow switch
Flue temperature probe NTC
Safety thermostat
Flame detection electrode
Room thermostat (if fitted)
External temperature probe (if fitted)
Time switch
On the Electronic control/ignition
p.c.b.......
Function control
C.h. temperature adjustment
D.h.w. temperature adjustment
Boiler reset button
(control panel fascia)
Inlet Information
Pump
Three way diverter valve
Gas valve
Fan
Ignition electrodes
Appliance operation lights*
L o c k --- o u t s i g n a l l a m p *
*control panel fascia
Outlet command
Fig. 9.1
The fundamental function of the Electronic control/igni-
tion p.c.b. is that of controlling the boiler in relation to
the external needs (i.e. heating the dwelling or heating
the water for d.h.w. use) and operating in order to keep
the temperature of the hydraulic circuits constant.
This is obviously possible within the useful power and
maximum working temperature limits foreseen.
Generally, the Electronic control/ignition p.c.b. receives
inlet information coming from the boiler (the sensors)
or from the outside (knobs, room thermostat, etc.), pro-
cesses it and consequently acts with outlet commands
on other components of the boiler (Fig. 9.1).
The Electronic control/ignition p.c.b. is also a full se-
quence ignition device and does a sequence of oper-
ations (ignition cycle) which lead to the ignition of the
gas at the burner
It checks the presence of the flame during the entire
period in which it is activated and supplies the fan regu-
lating its speed.
The Electronic control/ignition p.c.b. has a safety func-
tion and any incorrect interventions or tampering can
result in conditions of dangerous functioning of the
boiler.
The Electronic control/ignition p.c.b. can lock the func-
tioning of the boiler (lock state) and stop its functioning
up to the resetting intervention. The lock is signalled by
the lighting of the lock---out signal lamp and the device
can be reset only by using the boiler reset button
placed on the control panel fascia.
Some components which are connected to the device
can activate the lock state. The causes of a lock state
could be:
fThe intervention of the safety thermostat (over-
heat of the primary circuit).
fThe intervention of the flue temperature probe
(overheat of the combustion products).
fA fault on gas supply.
fFaulty ignition (faulty ignition electrodes, their wir-
ing or connection).
fFaulty flame detection (faulty detection electrode,
its wiring or connection).
fFaulty condensate drainage.
fFaulty gas valve (faulty on---off operators or not
electrically supplied).
fFaulty Electronic control/ignition p.c.b..
Other components like the primary circuit flow switch
can temporarily stop the ignition of the burner but allow
its ignition when the cause of the intervention has
stopped.
Fig. 9.13 and Fig. 9.14 show the sequence of the oper-
ations that are carried out at the start of every ignition
cycle and during normal functioning.
9.2 Selection and adjustment devices
On the Electronic control/ignition p.c.b. several selec-
tion, adjustment and protection devices are located.
(Fig. 9.2).
Some of these devices are directly accessible by the
user (function control, temperature adjustment poten-

Electronic control/ignition p.c.b.
16
tiometers etc.) others, like the fuses, are accessible by
removing the service panel.
91 7 84 5
12 1011131618 141517
32 6
Fig. 9.2
1 x7 connector --- electric supply terminal block and
external controls terminal block.
2 Fuse F1, F2 3,15 A F
3 Fuse F3, 400 mA T
4 x12 connector --- pump and 3way diverter valve
5 x17 connector --- gas valve
6 x14 connector --- external temperature probe
(optional)
7 x9 connector --- safety thermostat, flue tempera-
ture probe NTC, c.h. temperature probe NTC
8 x11 connector --- d.h.w. temperature probe
9 x10 connector --- d.h.w. flow switch
10 x2 connector --- timer
1 1 L o c k --- o u t s i g n a l l a m p
12 Boiler reset button
13 Function control / C.h. temperature adjustment
14 x22 connector --- fan
15 x24 connector --- transformer
16 D.h.w. temperature adjustment
17 x5 connector --- transformer
18 Appliance operation lights
9.3 Checking the temperature
The Electronic control/ignition p.c.b. makes it possible
to separately adjust the c.h. water flow temperature and
d.h.w. outlet temperature.
The temperature of the water is converted into an elec-
tric signal by means of temperature probes.
The user, setting the desired temperature with the con-
trol panel knobs operates the variable elements (13 and
16 in Fig. 9.2) of the electronic control p.c.b.
If the power requested is lower than 40% of the maxi-
mum power output then control is achieved by switch-
ing ON the burner at minimum power, then switching
OFF (ON/OFF function). If the power requested is
higher, then the burner is switched ON at maximum
power and will control by modulating to 40% of the
maximum power output.
During the c.h. operation (Fig. 9.3), the signal coming
from the c.h. temperature probe is compared to the sig-
nal given by the control panel through the adjustment
made by the user (knob ). The result of such a
comparison operates the fan speed thus regulating the
gas flow rate and consequently changing the useful
output of the boiler.
Fig. 9.3
When the boiler functions in d.h.w. (Fig. 9.4), the signal
coming from the d.h.w. temperature probe is compared

Electronic control/ignition p.c.b.
17
with the signal given by the control panel through the
adjustment made by the user (knob ).
90 ˚C
Fig. 9.4
Normally, the result of the comparison between these
two signals directly operates the fan speed adjusting
the useful output generated in order to stabilize the
temperature of the exiting water.
If during the d.h.w. mode operation, the temperature of
the primary circuit goes over 90°C, the useful output is
automatically reduced so that the primary circuit can-
not reach excessive temperatures.
The control sequences in function and in func-
tion are illustrated in detail in sections 9.10 and 9.11.
9.4 Operation lights
The Electronic control/ignition p.c.b. is provided with
three lamps (L.E.D. indicators) 18 in Fig. 9.2 that give
optical information during the operation of the boiler.
The green lamp on the left gives information whether
the boiler is in stand---by mode or during the normal
operation of the boiler.
The following table gives the relationship between the
lamps indication and their meaning.
A short pulse every 4 seconds
Boiler in stand --- by condition.
(function control in
position).
Anti---freeze system active.
1secondON1secondOFF
Boiler ON condition
(function control in or
position)
With the boiler switched ON ( or )allthelamps
(18 in Fig. 9.2) are activated.
The following table gives the relationship between each
of the possible lamp combinations and their meaning.
Normally operating boiler
(see the previous table for details)
C.h. operation
D.h.w. operation
Frost protect operation
D.h.w. operation
Excessive temperature on primary circuit
Faulty c.h. temperature probe NTC
Faulty d.h.w temperature probe NTC
Faulty flue temperature probe NTC
Faulty external temperature probe NTC
Faulty primary circuit
(no water or absence of flow)
Lack of burner ignition
Safety thermostat lock out
Faulty fan control system
Flue temperature probe NTC lock out
Flame detection error
Lack of power supply or faulty electronic
control p.c.b.
Faulty Electronic control/ignition p.c.b.. *
Lamp
OFF
Lamp
ON
Flashing lamp, alone
or simultaneously
with an other lamp.
Flashing lamp,
alternate with
another lamp.
* These conditions are normal only for a short time when the
power supply is applied to the boiler.
If permanent they indicate a faulty p.c.b.

Electronic control/ignition p.c.b.
18
9.5 Setting the boiler control function modes
It is possible to select the various boiler control function
modes by using the function selector knob A and the
D.h.w. temperature control knob B (Fig. 9.5).
During the function modes setting, the boiler does not
operate.
C
ED AB
Fig. 9.5
9.6 Adjustment of maximum useful output in
c.h. mode
The following procedure allows the output of the boiler
for c.h. to be limited to meet the system requirement.
Adjusting the maximum useful output in c.h. mode
does not prevent the boiler firing at maximum rate for
d.h.w. production.
1 Turn the boiler ON positioning the function selec-
tor knob A as indicated in Fig. 9.6.
C
ED A
B
Fig. 9.6
2 Keep pressed the reset button C for about 10 sec-
onds until the lock---out signal lamp D blinks.
3 The lamps E should give the indication as in
Fig. 9.7 (maximum c.h. useful output adjust-
ment). If not, press the reset button repeatedly to
obtain it.
Where: Lamp OFF
Lamp ON
Fig. 9.7
At this step it is possible to visualize the current setting
by keeping the reset button C pressed for more than 5
seconds. The lamps will flash a number of times corre-
sponding to the setting (Tab. 9.1).
4 To change the setting turn the knob B on a posi-
tion corresponding to the desired maximum use-
ful output (Tab. 9.1).
By turning the knob B, the lock--- out signal lamp
D blinks quickly (2 per seconds) indicating that
the setting has changed and must be memo-
rised.
Knob position Maximum useful output in c.h. mode
non condensing
kW (BTU/h)
M110.24SM/... M110.32SM/...
15,8 (19 788) 10,6 (36 165)
210,3 (35 142) 13,2 (45 036)
313,8 (47 083) 16,3 (55 612)
416,7 (56 977) 21,0 (71 648)
519,9 (67 895) 24,9 (84 954)
622,6 (77 107) 29,2 (99 625)
724,4 (83 248) 32,7 (111 566)
Ta b . 9 . 1
5 To memorize the setting keep pressed the reset
button C for about 5 seconds until the lights E
briefly blinks simultaneously.
6 To reset the boiler to the normal operation turn it
OFF and ON by the function selector knob A. In
any case, the boiler automatically resets to its nor-
mal operation after 10 minutes.
9.7 Reignition frequency setting
It is possible to select the minimum time that must pass
between two ignitions of the burner in c.h. function
mode.
1 Turn the boiler ON positioning the function selec-
tor knob A as indicated in Fig. 9.8.
C
ED A
B
Fig. 9.8
2 Keep pressed the reset button C for about 10 sec-
onds until the lock---out signal lamp D blinks.
3 The lamps E should give the indication as in
Fig. 9.9 (reignition frequency). If not, press the
reset button repeatedly to obtain it.
Where: Lamp OFF
Lamp ON
Fig. 9.9
At this step it is possible to visualize the current setting
by keeping the reset button C pressed for more than 5
seconds. The lamps will flash a number of times corre-
sponding to the setting (Fig. 9.10).
4 To change the setting turn the knob B on a posi-
tion corresponding to the desired delay.
By turning the knob B, the lock--- out signal lamp
D blinks quickly (2 per seconds) indicating that
the setting has changed and must be memo-
rised.