Biasi M110B.24SM/E User manual

Wall hung, fanflue, roomsealed, high efficiency gas boiler
Service manual
GARDA PLUS HE
Models G.C. Appl. No.
M110B.24SM/E 47---583---13
M110B.32SM/E 47---583---14
Leave this manual adjacent to the gas meter
Warning:
Service / repairs must be carried out, only by a qualified Gas Safety
Registered Engineer, who will be responsible for the current Regulations for
gas appliances.
Note:
After servicing, complete the relevant Service Interval Record section of the
Benchmark Checklist of the user and installation manual.

- 3 -
TABLE OF CONTENTS
1 OVERALL INFORMATION..........................4
1.1 Overall View .....................................4
1.2 Hydraulic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 GENERAL ACCESS AND EMPTYING HYDRAULIC CIR-
CUITS ..........................................5
2.1 Nomenclature ....................................5
2.2 Body panels......................................5
2.3 Control panel .....................................5
2.4 Access to the sealed chamber .......................6
2.5 Emptying the primary circuit .........................6
2.6 Emptying the d.h.w. circuit...........................6
3 DIAGRAMS .....................................7
3.1 Wiring diagram M110B.24SM/... M110B.32SM/... .........7
3.2 Circuit voltages ...................................8
4 FAULT FINDING..................................9
5 CONDENSING HEAT EXCHANGER .................11
5.1 Function........................................11
5.2 Removal .......................................11
5.3 Cleaning .......................................12
6 D.H.W. HEAT EXCHANGER .......................13
6.1 Function........................................13
6.2 Removal .......................................13
7 PUMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
7.1 Function........................................14
7.2 Checks.........................................14
7.3 Removal .......................................14
8 THREE WAY DIVERTER VALVE ....................15
8.1 Function........................................15
8.2 Checks.........................................15
8.3 Removal of the electric actuator .....................15
8.4 Removal of the diverter group and its internal parts ......16
9 ELECTRONIC CONTROL/IGNITION P.C.B. ...........17
9.1 Function........................................17
9.2 Selection and adjustment devices....................17
9.3 Checking the temperature ..........................18
9.4 Operation lights ..................................19
9.5 Setting the boiler control function modes ..............19
9.6 Adjustment of maximum useful output in c.h. mode ......19
9.7 Reignition frequency setting ........................20
9.8 Checks.........................................20
9.9 Removal of the electronic control p.c.b ................20
9.10 Thermal control in the " "mode ....................22
9.11 Thermal control in the " " mode ...................23
10 TRANSFORMER ................................24
10.1 Removal .......................................24
10.2 Check the transformer.............................24
11 GAS VALVE ....................................25
11.1 Function........................................25
11.2 Nomenclature of the parts ..........................25
11.3 Adjustment......................................25
11.4 Checks.........................................26
11.5 Removal of the gas valve ..........................26
12 PRIMARY CIRCUIT FLOW SWITCH .................28
12.1 Function........................................28
12.2 Checks.........................................28
12.3 Removal .......................................28
13 EXPANSION VESSEL AND TEMPERATURE-PRESSURE
GAUGE........................................30
13.1 Function........................................30
13.2 Checks.........................................30
13.3 Removal of the expansion vessel ....................30
13.4 Removal of the temperature-pressure gauge ...........30
14 D.H.W. FLOW SWITCH, FILTER AND FLOW LIMITER ..31
14.1 Function........................................31
14.2 Nomenclature and location of parts...................31
14.3 Checks.........................................31
14.4 Removal of the sensor.............................31
14.5 Removaloftheowswitchgroupandd.h.w.circuitlter ..31
14.6 Flow limiter .....................................32
15 TEMPERATURE PROBE..........................33
15.1 Function........................................33
15.2 Checks.........................................33
15.3 Removal of the c.h. Temperature probe ...............33
15.4 Removal of the d.h.w. Temperature probe..............33
16 BY-PASS VALVE ................................34
16.1 Function........................................34
16.2 Removal .......................................34
17 FAN AND AIR BOX ..............................35
17.1 Function........................................35
17.2 Removal of the Air box and 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 spark generator .....................38
18.7 Checks.........................................38
19 SAFETY THERMOSTAT ..........................39
19.1 Function........................................39
19.2 Checks.........................................39
19.3 Removal .......................................39
20 FLUE TEMPERATURE PROBE NTC AND SAFETY THER-
MAL FUSE .....................................40
20.1 Function........................................40
20.2 Removal .......................................40
20.3 Checks.........................................40
21 CONDENSATE TRAP ............................41
21.1 Function........................................41
21.2 Check the cleanness of the trap .....................41
21.3 Removal .......................................41
22 SHORT SPARE PARTS LIST ......................42

- 4 -
OVERALL INFORMATION
1 OVERALL INFORMATION
1.1 Overall View
Figure 1.1
D.h.w.
heat exchanger
Expansion
vessel
Condensate
trap
Ignition
electrodes
Gas valve
Control
panel
Automatic
air purger
valve
Pump
Condensing
heat exchanger
Gas restrictor
Transformer
D.h.w. Flow
Switch
Spark
Generator
C.h. pressure
relief valve
Safety thermal
fuse
Fan
Safety
thermostat
Burner
D.h.w. temp.
probe
Detection
electrode
Diverter valve
Main circuit
flow switch
Flue temperature
probe NTC
C.h. temp.
probe
Air box
Condensing heat
exchanger air
purger valve
Air hose
Codensate
trap
1.2 Hydraulic diagram
Figure 1.2
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

- 5 -
GENERAL ACCESS AND EMPTYING HYDRAULIC CIRCUITS
2 GENERAL ACCESS AND EMPTYING HYDRAU-
LIC CIRCUITS
2.1 Nomenclature
Figure 2.1
6
1
2
3
45
1 Right side panel
2 Front panel
3 Control panel lid
4 Control panel cover
5 Service panel
6 Left side panel
2.2 Body panels
Warning: isolate the boiler from the mains electrici-
ty supply before removing any covering or compo-
nent.
For the most part of the check and maintenance operations it is
necessary to remove one or more panels of the case.
The side panels can be removed only after the removal of the
front panel.
To remove the front panel remove screws A(Figure 2.2), lift the
panel and remove it.
Figure 2.2
A
To remove the side panels loosen the screws Cand D(Figure
2.3), bring the base of the panels away from the boiler and lift
them, freeing them from the top hooks.
Figure 2.3 - Bottom view of the boiler
B
C
D
C
2.3 Control panel
Warning: isolate the boiler from the mains electrici-
ty supply before removing any covering or compo-
nent.
To gain access to the parts located inside the control panel pro-
ceed as follows:
1 Remove the front panel of the case
2 Loosen the screws C and D (Figure 2.3).
3 Remove the screws B.
4 Move the lower part of the side panels as indicated in Figure
2.4 and pull the control panel.
When completely pulled out, the panel can rotate 45° down-
wards to facilitate the service operations on the internal parts.
Figure 2.4
5 Remove the screws E and remove the service panel (Figure 2.5);

- 6 -
GENERAL ACCESS AND EMPTYING HYDRAULIC CIRCUITS
6 Remove the screws Fand remove the control panel lid (Fig-
ure 2.5).
Figure 2.5
E
F
F
2.4 Access to the sealed chamber
Figure 2.6
G
G
To gain access to the parts contained in the sealed chamber it is
necessary to remove the lid of the sealed chamber. For this pur-
pose, remove the front and side panels of the case, remove the
screws G as indicated in Figure 2.6 and remove the lid.
2.5 Emptying the primary circuit
1 Closethec.h.circuitowandreturncocksH.(Figure2.7).
Figure 2.7
H
I
H
- Bottom view of the boiler
2 Remove the front and right panels of the boiler.
3 Open the drain tap J(Figure 2.8) until the boiler is completely
emptied.
Figure 2.8
J
4 To help the draining of the primary circuit loose the condens-
ing heat exchanger air purger valve K (Figure 2.9).
Figure 2.9
K
Attention: some water could remain in the condensing heat
exchanger.
5 Close drain tap once the emptying has been completed.
2.6 Emptying the d.h.w. circuit
1 Close the d.c.w. inlet cock I (Figure 2.7).
2 Open one or more hot water taps until the boiler has been
completely emptied.

- 7 -
DIAGRAMS
3 DIAGRAMS
3.1 Wiring diagram M110B.24SM/... M110B.32SM/...
Figure 3.1
Ignition
electrodes
Flamedetection
electrode
Externalcontrols
terminal block
Electric supply
terminal blockThreeway
diverter valve
Pump
Fan
Primarycircuit
flow switch
D.h.w. flow
switch
C.h. temperature
probeNTC
Gasvalve
Safety
thermostat
Flue
temperature
D.h.w. temperature
probeNTC
probeNTC
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
bu bn
bu
bn
nbnbubub
LN
gnye bu bn
bn
bkbu
bn bu
gnye
bn bk bu
bn
gnye bu
gnye
ubnbrd wh bk bu bn
gnye
gnye
bu
bn
bu
1
4
5
bu bn
bn bu
whog
wh
gy
t
t
bk rd
rd
bk
bu
bu
bu bu
wh
bu
wh
bu
M
~
rdbk
bugy
wh
rd
gy
bu
wh
bk
t
bk
wh
wh
bk
bkwh
NO
COM
rd
rd
rd
rd
gy gy
gy
gy
Transformer
230V~/24V~
Spark
Generator
Time switch
rd
gn
bk
bn =brown
bu =blue
bk =black
wh =white
rd =red
gy =grey
gn =green
ye =yellow
vt =violet
og =orange
gnye =green/yellow
rdwh =red/white
bn
hwhw
Safety
thermalfuse
t
gy
gy
wh
M
~3
2
1
321rdbk
wh
wh

- 8 -
DIAGRAMS
3.2 Circuit voltages
Figure 3.2
Electrical voltages with burner on
duringc.h.ord.h.w.operation
only during c.h. operation
only during d.h.w. operation
230~
Safety
thermostat
0
Fan
0
Main circuit
3DL2DL1DL
2F1F
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
Supplynetwork
230~
Pump
230~0
230~0
3way
diverter valve
230~
Gasvalve
24~
Transformer
24=
230~
0
5=
D.h.w.
Flow switch
pressure switch

- 9 -
FAULT FINDING
Components to check
Sectionofthe manual
(noteref.inbrackets)
10 ---
(1)
---
(
NO TAG
)
---
(3)
21.1 ---
(4)
67.28.29.911.4 12.2 14.5 15.2 16 17 18.7 18.7 19.2 19.2 20.1 ---
(7)
--- ---
Lock--- outsignallampred
Defect


Transformer
Powersupplyline
Gassupplyline
Flue pipes
Condensate drainpipeand trap
C.h. circuit
D.h.w. circuit
D.h.w. heat exchanger
Pump
Divertervalve
D.h.w. flow switch
Fuses(Electronic p.c.b.)
Electronic p.c.b.
Boiler settings
Gasvalve
Main circuitflowswitch
D.h.w. filter
Main circuittemp. probe
D.h.w. temp.probe
By---passvalve
Fanair restrictor
Sparkgenerator
Ignition electrode
Detectionelectrode
Safety thermostat
Gasrestrictor
Flue temperatureprobe NTC
Expansionvessel
Safety valve
Pressure gauge
By pressing thereset push--- button
theboilerturns on andoperatescor-
rectly.
         
By pressing thereset push--- button
theboilerstartsthe ignition cycle.
Theburnerdoesn’tlight on andthe
boiler locksagain.
          
ON
By pressing thereset push--- button
theboilerstartsthe ignition cycle. Theburnerlightsonand theboiler
locksagain.
    
Theboilerdoesnot starteitherinc/h or d.h.w. mode. Allthe operationlightsOFF
Fanstill.
  
Theburnerdoesn’t lighteitherinc.h.
or d.h.w. mode. Fanturns.
   
Theburnerdoesn’t lighteitherinc.h.
or d.h.w. mode. Fandoesn’tturn.
    
Theboilerdoesn’t controlthe d.h.w. temperature. Turningthe d.h.w. temp.adjustment
knob hasn’t effect on themodulation
of theflame. Theboileroperatescorrectlyonc.h.
 
OFF
Theboilerlightsfor ashort whileon
c.h. Normal operationond.h.w.function.
    
4 FAULT FINDING

- 10 -
FAULT FINDING
Components to check
Sectionofthe manual
(noteref.inbrackets)
-----
--
--
(7)
2.912.911.0218.718.7617115.24.112.215.419.92.72.86---
(4)
21.1---
(3)
---
(
NO TAG
)
---
(1)
10
Lock---out signal lamp red
Pressure gauge
Safety valve
Expansionvessel
Flue temperatureprobe NTC
Gasrestrictor
Safety thermostat
Detection electrode
Ignition electrode
Sparkgenerator
Fanair restrictor
By---passvalve
D.h.w. temp.probe
Main circuittemp. probe
D.h.w. filter
Main circuitflowswitch
Gasvalve
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
Condensatedrain pipe andtrap
Flue pipes
Gassupply line
Powersupply line
Transformer
Defect
Theboilerdoesnot supply d.h.w.
(cold waterfromthe tap). Regularoperation in c/hmodeeven
during adrawing offd.h.w.
  
On c/hmodethe temperatureofthe
main circuitreaches 90Cand thec/h
system does notheat.
Theboileroperatescorrectlyon
d.h.w. mode.
  
Incorrectmodulation   
Noisybolier     
Poor c.h. /d.h.w.temperature (9)    
F
Poor d.h.w. temperature. Regular operationinc/h mode.
  
(8)

OF
F
Lowd.h.w.flowrate   
---
Waterleaks from thesafetyvalve dur-
ingoperation on c/h
  
---
Waterleaks from thesafetyvalve
when theboilerisoff.
 
Note Useful informationcan be obtained also from the
opticalindicationgiven by theapplianceoper-
ationlights(seesection 9.4).
1Check for230V~ betweenline(L) andneutral (N)
Verify theintegrity of supply cable, plug andexternalfuses.
Checkthe polarity of line andneutral connection
2Check thegas supplypipeand isolationtap forgas tightness.
3Check forsoundness andabsence of obstructions.Verifythat
theflueterminal is correctly installed(seeclearances) anden-
sure that exhaustgas is notsuckedbackbythe boiler.
4Check forsoundness of thecircuit andverifyits correct filling
(see also installation manual).
5Ajammed by--- pass couldcause theover--- heatingofthe main
circuitand theinterventionofthe safety thermostat.
6Using theflueanalyzer,check theCO2valueofthe flue gases.
This readingisareferencevalue forthe gas valvesetting.
7Check thepressurization of theexpansion vessel.Refer to the
installation manual forpropervalues.
8d.h.w.pressure toohighorflowratetoo high.Ifnecessary in-
sert aflowratelimiter (14.6).
9The boiler doesn’treachthe nominalheatinput.



- 11 -
CONDENSING HEAT EXCHANGER
5 CONDENSING HEAT EXCHANGER
5.1 Function
The Condensing heat exchanger Ain Figure 5.1 has the function
of transferring heat produced from combustion of the gas and
fromtheueexhaustedgastothewatercirculatinginit.
Figure 5.1
A
B
C
By reducing the combustion products temperature, the latent
heat of the vapour is transferred to the water circuit, allowing an
extra gain of useful heat.
The condensed vapour is then drained through the condensate
trap B and 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uesystemfromtheboiler.
2 Remove the fan group (rubber pipe, gas pipe) following the
instructions from 1 to 6 in section "Removal of the Air box and
the Fan" page 35.
3 Disconnect the detection electrode connector D, the ignition
electrodes connector E and the earth wire F.
4 Disconnect the fan connector Gby pressing the plastic hook
placed on the side of the connector (Figure 5.2).
5 Unscrew the nuts H (Figure 5.2).
6 Remove the fan-burner group I.
7 Empty the primary circuit of the boiler.
8 Remove the clips J (Figure 5.2).
9 Loosen the connection Kand slightly move the pipe Lup-
wards, turn it towards left (Figure 5.2) and then move the pipe
downwards freeing it from the Condensing heat exchanger.
10 Loosen the connection Mand slightly move the pipe Nup-
wards, turn it towards left (Figure 5.2) and then move the pipe
downwards freeing it from the Condensing heat exchanger.
Figure 5.2
D
E F
G
H
I
J
KLM N
Figure 5.3
O
P
Q
R
11 Using pliers, remove the spring Omoving it downwards and
disconnect the rubber pipe P (Figure 5.3).
12 Unscrew the screws Q and remove the clamps (Figure 5.3).
13 Disconnect the two connectors Rby pressing the plastic hook
placed on the side of the connector (Figure 5.3).

- 12 -
CONDENSING HEAT EXCHANGER
14 Remove the Condensing heat exchanger by levering it and
sliding it forwards.
15 Reassemble the Condensing heat exchanger carrying out
the removal operations in reverse order.
Ensure to tighten the nuts H - Figure 5.2 rmly.
5.3 Cleaning
If there are deposits of dirt on the coil of the Condensing heat
exchanger, clean with a bristle paintbrush and remove the dust
with a hoover.
Warning: After cleaning or replacement as detailed
above, if it deemed necessary to undertake a com-
bustion analysis as detailed in chapter 11.3 section
11.
Figure 5.4
S
Caution:
After any periodical servicing or disturbance the combustion
chamber silicon seal S Figure 5.4 must be fully inspected and
replaced at the discretion of the service engineer.
After any disturbance to the chamber door seal the appliance
must undergo a full analytical combustion performance check.

- 13 -
D.H.W. HEAT EXCHANGER
6 D.H.W. HEAT EXCHANGER
6.1 Function
The d.h.w heat exchanger Ain Figure 6.1 and Figure 6.3 allows
the instantaneous transfer of heat from the primary hydraulic cir-
cuit to the water destined for d.h.w use.
Figure 6.1
A
The schematic structure is shown in Figure 6.2.
Figure 6.2
Primaryhydraulic circuit
Domestic hotwater circuit
6.2 Removal
Warning: isolate the boiler from the mains electrici-
ty supply before removing any covering or compo-
nent.
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 Allen key screws Bin Figure 6.3
which hold the exchanger to the brass group.
4 Remove the electric actuator following the instructions in sec-
tion "Removal of the electric actuator" page 15.
Figure 6.3
B
A
5 Remove the pump following the instructions in section "Re-
moval" page 14.
6 Completely unscrew the Allen key screws C(Figure 6.4)
which hold the exchanger to the plastic groups.
Figure 6.4
A
C
7 Move the exchanger towards the rear of the boiler and extract
it to the left.
Reassemble the d.h.w. heat exchanger carrying out the removal
operations in the reverse order.
W arning: to lubricate the O-ring gaskets exclusively
use a silicone base grease compatible to be in con-
tact with foods and approved by the local water Au-
thorities.
Warning: When reassembling the exchanger be sure
to put the off center location/securing pin indicated
in Figure 6.5 towards the left side of the boiler.
Figure 6.5

- 14 -
PUMP
7 PUMP
7.1 Function
The pump Ain Figure 7.1 and Figure 7.2 has the function of mak-
ing the water in the main circuit circulate through the main con-
densing heat exchanger and therefore through the c.h. system
(during the c.h. function) or through the secondary heat exchang-
er (during the d.h.w. function).
Figure 7.1
A
7.2 Checks
Warning: isolate the boiler from the mains electricity
supply before removing any covering or component.
Check that the pump is not seized and that the movement of
the rotor is not subject to mechanical impediments.
With the boiler off, remove the front panel. Remove the air re-
lease plug of the pump and turn the rotor with a screwdriver.
Check the electrical continuity.
With the boiler off, remove the front panel and disconnect the
connector B (Figure 7.2).
Measure the electrical resistance between the pump supply con-
nections.
Electrical resistance of the windings (at ambient temperature)
mustbeabout230Ω.
Check 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 direction of the arrow.
If there is a defect in starting, the rotor will begin to turn normally
only starting it manually.
Check that the impeller is integral with the rotor.
With the boiler off remove the front and right hand side case pan-
els, lower the control panel and empty the primary circuit.
Remove the pump head by undoing the screws which hold it to the
pumpbodyandcheckthattheimpellerisrmly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 (Figure 7.2).
5 Loosen the connection C,and pull up and turn to the left the
pipe D.
Figure 7.2
B
C
D
E
F
A
6 Remove the locking plate E.
7 Unscrew the two screws Fthat hold the pump on the frame
and remove the pump.
Reassemble the pump carrying out the removal operations 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 plastic group.

- 15 -
THREE WAY DIVERTER VALVE
8 THREE WAY DIVERTER VALVE
8.1 Function
The diverter valve A(Figure 8.1) has the function of modifying 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 exchanger towards the c.h. system or
towards the d.h.w. heat exchanger.
Figure 8.1
A
8.2 Checks
Warning: check the electrical continuity.
Figure 8.2 indicates the relationship between the electric com-
mand 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.
Figure 8.3 indicates the relationship between the electric com-
mand 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gurestherelationshipbetweenthepositionoftheactua-
tor and the resistance of the motor windings (the motor must be
disconnected from the wiring) is also given.
Figure 8.2
rd =red
bk =black
wh =white
0V
230V
SpindleB
notvisible
Open circuit
9,4Kohm
wh
rd
bk
3
1
2
B
- D.h.w. mode
Figure 8.3
rd =red
bk =black
wh =white
230 V
0V
SpindleB
visible
Open circuit
9,4Kohm
wh
rd
bk
3
1
2
B
- C.h. mode
8.3 Removal of the electric actuator
Warning: isolate the boiler from the mains electrici-
ty supply before removing any covering or compo-
nent.
1 Remove the front case panel.
2 Disconnect the connectors C (Figure 8.4).
3 RemovethexingspringD and remove the actuator E.
Reassemble the actuator carrying out the removal operations
in the reverse order.
When reassembling the actuator, refer to Figure 8.2 or to the
wiring diagram in section "Checks" page 15 for the correct
wiring connection.

- 16 -
THREE WAY DIVERTER VALVE
Figure 8.4
C
D
E
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 (section "Removal of the elec-
tric actuator" page 15).
4 RemovethexingspringF(Figure 8.5) and remove the pri-
marycircuitowswitchG.
5 Disconnect both c.h. and d.h.w. temperature probe, respec-
tively H and I.
6 Unscrew the connector J, the c.h. ow connector and the
d.h.w. outlet connector.
Figure 8.5
F
G
H
I
J
7 Remove the d.h.w. heat exchanger (see section "Removal"
page 13).
8 Remove the fork K and move away the pipe L (Figure 8.6).
9 Unscrew the screw M and remove the diverter group.
Figure 8.6
K
L
M
10 Refer to the exploded view in Figure 8.7 to remove the inter-
nal parts of the three way diverter valve.
Figure 8.7
11 Reassemble the diverter group carrying out the removal op-
erations in the reverse order.
W arning: to lubricate the O-ring gaskets exclusively
use a silicone base grease compatible to be in con-
tact with foods and approved by the local water Au-
thorities.

- 17 -
ELECTRONIC CONTROL/IGNITION P.C.B.
9 ELECTRONIC CONTROL/IGNITION P.C.B.
9.1 Function
Figure 9.1
From otherboilerdevices....
C.h. temperatureprobe NTC
D.h.w. temperatureprobe NTC
D.h.w. flow switch
Primarycircuit flow switch
Flue temperatureprobe NTC
Safety thermalfuse
Safety thermostat
Flamedetection electrode
Room thermostat (iffitted)
Time switch
On theElectroniccontrol/ignition
p.c.b.......
Function control
C.h. temperatureadjustment
D.h.w. temperatureadjustment
Boiler resetbutton
(control panelfascia)
InletInformation
Pump
Threeway diverter valve
Gasvalve
Fan
Ignition electrodes
Applianceoperation lights*
Lock--- outsignallamp*
*control panelfascia
Outlet command
The fundamental function of the Electronic control/ignition 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 cir-
cuits 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.), processes it and conse-
quently acts with outlet commands on other components of the
boiler (Figure 9.1).
The Electronic control/ignition p.c.b. is also a full sequence igni-
tion device and does a sequence of operations (ignition cycle)
which lead to the ignition of the gas at the burner.
Itchecksthe presence of the ame during theentire period in
which it is activated and supplies the fan regulating its speed.
The Electronic control/ignition p.c.b. has a safety function 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 functioning 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 acti-
vate the lock state. The causes of a lock state could be:
• The intervention of the safety thermostat (overheat of the pri-
mary circuit).
• Theinterventionoftheuetemperatureprobe(overheatofthe
combustion products).
• A fault on gas supply.
• Faulty ignition (faulty ignition electrodes, their wiring or connection).
• Faultyamedetection (faultydetectionelectrode,itswiringor
connection).
• Faulty condensate drainage.
• Faulty gas valve (faulty on-off operators or not electrically supplied).
• Faulty Electronic control/ignition p.c.b.
Othercomponentsliketheprimarycircuitowswitchcantempo-
rarily stop the ignition of the burner but allow its ignition when the
cause of the intervention has stopped.
Figure 9.15 and Figure 9.16 show the sequence of the opera-
tions 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 selection, adjust-
ment and protection devices are located. (Figure 9.2).
Some of these devices are directly accessible by the user (func-
tion control, temperature adjustment potentiometers etc.) others,
like the fuses, are accessible by removing the service panel.

- 18 -
ELECTRONIC CONTROL/IGNITION P.C.B.
Figure 9.2
1 2 3 4 5 6 7 8 9 10 11
121314151617181920
1 x7 - x16 connector - electric supply terminal block and exter-
nal controls terminal block.
2 Fuse F1, F2 3,15 A F
3 Fuse F3, 400 mA T
4 x15connector-amedetectionelectrode
5 x12 connector - pump and 3 way diverter valve
6 x17 connector - gas valve
7 x14 connector - external temperature probe (optional)
8 x9 connector - safety thermostat, ue temperature probe
NTC, c.h. temperature probe NTC
9 x11 connector - d.h.w. temperature probe
10 x10connector-d.h.w.owswitch
11 x13 connector - remote control (optional)
12 x2 connector - timer
13 Lock-out signal lamp
14 Boiler reset button
15 Function control / C.h. temperature adjustment
16 x22 connector - fan
17 x6 connector - spark generator
18 D.h.w. temperature adjustment
19 x5 - x24 connector - transformer
20 Appliance operation lights
9.3 Checking the temperature
The Electronic control/ignition p.c.b. makes it possible to sepa-
rately adjust the c.h. water ow temperature and d.h.w. outlet
temperature.
The temperature of the water is converted into an electric signal
by means of temperature probes.
The user, setting the desired temperature with the control panel
knobs operates the variable elements (15 and 18 in Figure 9.2)
of the electronic control p.c.b.
If the power requested is lower than 40% of the maximum power
output then control is achieved by switching 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 (Figure 9.3), the signal coming from the
c.h. temperature probe is compared to the signal 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owrateandconsequentlychangingthe
useful output of the boiler.
Figure 9.3
When the boiler functions in d.h.w. (Figure 9.4), the signal com-
ing from the d.h.w. temperature probe is compared with the sig-
nal given by the control panel through the adjustment made by
the user (knob ).
Figure 9.4
90°C

- 19 -
ELECTRONIC CONTROL/IGNITION P.C.B.
Normally, the result of the comparison between these two signals
directly operates the fan speed adjusting the useful output gen-
erated in order to stabilize the temperature of the exiting water.
If during the d.h.w. mode operation, the temperature of the pri-
mary circuit goes over 90°C, the useful output is automatically
reduced so that the primary circuit cannot reach excessive tem-
peratures.
The control sequences in function and in function are
illustrated in detail in sections 9.10 and 9.11page 23.
9.4 Operation lights
The Electronic control/ignition p.c.b. is provided with three lamps
(L.E.D. indicators) 20 in Figure 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 in-
dication and their meaning.
A short pulse every 4 seconds
1 second ON 1second OFF
Boiler in stand-by condition.
(function control in
position).
Anti- freeze system active.
A
short pulse every 4 seconds
1 second ON 1second OFF
Boiler ON condition
(function control in or
position)
With the boiler switched ON ( or ) all the lamps (20 in Fig-
ure 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 primary circuit
(nowaterorabsenceofow)
Lack of burner ignition
Safety thermostat lock out
Faulty fan control system
Flue temperature probe NTC lock out
OpenuetemperatureprobeNTC
Faulty external temperature probe NTC
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 another 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.
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 7and the D.h.w. temperature
control knob 8 (Figure 9.5).
During the function modes setting, the boiler does not operate.
Figure 9.5
78 9 1011
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 maxi-
mumusefuloutputinc.h.modedoesnotpreventtheboilerring
at maximum rate for d.h.w. production.
1 Turn the boiler ON positioning the function selector knob 7as
indicated in Figure 9.6.
Figure 9.6
11 8 7 9 10
2 Keep pressed the reset button 9for about 10 seconds until
the lock-out signal lamp 10 blinks.
3 The lamps 11 should give the indication as in Figure 9.7
(maximum c.h. useful output adjustment). If not, press the
reset button repeatedly to obtain it.

- 20 -
ELECTRONIC CONTROL/IGNITION P.C.B.
Figure 9.7
Where: Lamp OFF
Lamp ON
At this step it is possible to visualize the current setting by keep-
ing the reset button 9pressed for more than 5 seconds. The
lampswillashanumberoftimescorrespondingtothesetting
(Figure 9.8 and Figure 9.9).
4 To change the setting turn the knob 8on a position corre-
sponding to the desired maximum useful output (Figure 9.8
and Figure 9.9). By turning the knob 8, the lock-out signal
lamp 10 blinks quickly (2 per seconds) indicating that the set-
ting has changed and must be memorised.
Figure 9.8
Knob position
Maximum useful output in c.h. mode non
condensing - kW (BTU/h)
M110B.24SM/... M110B.32SM/...
1 5,8 (19 789) 8,2 (27 977)
2 9,0 (30 707) 12,4 (42 307)
3 12,2 (41 625) 16,5 (56 296)
4 15,5 (52 884) 20,7 (70 626)
5 18,7 (63 802) 24,8 (84 614)
6 21,9 (74 720) 29,0 (98 944)
7 25,1 (85 638) 33,1 (112 933)
Figure 9.9
8
5 To memorize the setting keep pressed the reset button 9for
about 5 seconds until the lights 11brieyblinkssimultaneously.
6 To reset the boiler to the normal operation turn it OFF and
ON by the function selector knob 7. In any case, the boiler
automatically resets to its normal 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 selector knob 7as
indicated in Figure 9.10.
Figure 9.10
11 78 9 10
2 Keep pressed the reset button 9for about 10 seconds until
the lock-out signal lamp 10 blinks.
3 The lamps 11 should give the indication as in Figure 9.11
(reignition frequency). If not, press the reset button repeat-
edly to obtain it.
Figure 9.11
Where: Lamp OFF
Lamp ON
At this step it is possible to visualize the current setting by keep-
ing the reset button 9pressed for more than 5 seconds. The
lampswillashanumberoftimescorrespondingtothesetting
(Figure 9.12).
4 To change the setting turn the knob 8on a position corre-
sponding to the desired delay.
By turning the knob 8, the lock-out signal lamp 10 blinks quick-
ly (2 per seconds) indicating that the setting has changed and
must be memorised.
Figure 9.12
Delay (minutes)
Setting No.
0
1 1/2
3
4
5 1/2
7
8 1/2
8
5 To memorize the setting keep pressed the reset button 9for
about 5 seconds until the lights 11brieyblinkssimultaneously.
6 To reset the boiler to the normal operation turn it OFF and
ON by the function selector knob 7. In any case, the boiler
automatically resets to its normal operation after 10 minutes.
Factory setting = 3 minutes
9.8 Checks
Check that the fuses are complete
If the Electronic control/ignition p.c.b. does not supply any device
(pump, fan, etc.) check that the fuses 2and 3(Figure 9.2) are
complete.
If a fuse has blown replace it with one that has the same charac-
teristicsafterhavingidentiedthereasonforfailure.
Lock sequence
Start the boiler until the burner is ignited.
With the burner ring, interrupt the gas supply. The Electronic
control/ignition p.c.b. must carry out three complete ignition cy-
cles and then, after about 3 minutes, goes to lock-out state.
By turning the boiler on and off by means of the function switch
the device must not unlock and the burner must not turn on.
9.9 Removal of the electronic control p.c.b
Warning: isolate the boiler from the mains electrici-
ty supply before removing any covering or compo-
nent.
When replacing the Electronic control/ignition p.c.b. it is ad-
visable to go through the setting modes of the boiler here
described in sections 9.5 to 9.7.