Biasi M96A.24SM/B User manual

Wall hung, fan flue, room sealed, high efficiency gas boiler
Service manual
GARDA HE MK2
Models: G.C. Appl. No.
M96A.24SM/B 47---583---15 Combi boiler
M96A.28SM/B 47---583---16 Combi boiler
Leave this manual adjacent to the gas meter

Ta b l e 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 3............
3Diagrams 4...........................
3.1 Wiring diagram 4.......................
3.2 Functional flow diagrams 5..............
3.3 Circuit voltages 6......................
4Faultfinding 7........................
5 Primary heat exchanger 9..............
5.1 Function 9.............................
5.2 Removal 9............................
5.3 Cleaning 9............................
6 Condensing heat exchanger 11..........
6.1 Function 11.............................
6.2 Removal 11............................
6.3 Cleaning 11............................
7 D.h.w. heat exchanger 13...............
7.1 Function 13.............................
7.2 Removal 13............................
8Pump 14...............................
8.1 Function 14.............................
8.2 Checks 14.............................
8.3 Removal 14............................
9 Three way diverter valve 16.............
9.1 Function 16.............................
9.2 Checks 16.............................
9.3 Removal of the electric actuator 16........
9.4 Removal of the tree way diverter valve 17..
9.5 Removal of the diverter group 17..........
10 Electronic control/ignition p.c.b. 18......
10.1 Function 18.............................
10.2 Selection and adjustment devices 18......
10.3 Checking the temperature 19.............
10.4 Operation lights 20......................
10.5 Setting the boiler control function modes 21
10.6 Useful output setting 21..................
10.7 Reignition frequency setting 22...........
10.8 Ignition gas pressure adjustment 22.......
10.9 Setting the tree way diverter valve
operation mode 23......................
10.10 Checks 23.............................
10.11 Removal of the electronic control p.c.b 24..
10.12 Thermal control in the ” ”mode 25......
10.13 Thermal control in the ” ”mode 25......
10.14 Ignition and control sequence 26..........
11 Modulating gas valve 27................
11.1 Function 27.............................
11.2 Nomenclature of the parts 27.............
11.3 Adjustment 27..........................
11.4 Checks 28.............................
11.5 Removal of the on---off operators coils 28..
11.6 Removal of the gas valve 28..............
12 Primary circuit pressure switch 29.......
12.1 Function 29.............................
12.2 Checks 29.............................
12.3 Removal 29............................
13 Expansion vessel and
temperature -- pressure gauge 29........
13.1 Function 29.............................
13.2 Checks 29.............................
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 flow switch group
and d.h.w. circuit filter 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 35......................
16.1 Function 35.............................
16.2 Removal 35............................
17 Fan and Air pressure sensor 36.........
17.1 Function 36.............................
17.2 Checks 36.............................
17.3 Removal of the Fan 37...................
17.4 Removal of the Air pressure sensor 37.....
18 Ignition and detection electrodes 38.....
18.1 Function 38.............................
18.2 Checks 38.............................
18.3 Removal 38............................
19 Safety thermostat 39...................
19.1 Function 39.............................
19.2 Checks 39.............................
19.3 Removal 39............................
20 Flue temperature probe NTC 40.........
20.1 Function 40.............................
20.2 Checks 40.............................
20.3 Removal 40............................
21 Condensate trap 42....................
21.1 Function 42.............................
21.2 Removal 42............................
22 Short spare parts list 44................

1
1Overall information
1.1 Overall View
Fan
Safety
thermostat
Main heat
exchanger
Burner
Ignition
electrodes
Gas valve
Control
panel
Combustion
chamber
Automatic
air release
Pump
D.h.w. temp.
probe
D.h.w.
heat exchanger
Expansion
vessel
Detection
electrode
valve
Condensing
Diverter valve
Flue temperature
probe NTC
Primary circuit
heat exchanger
Condensate
trap
pressure switch
Air pressure sensor
C.h. temp.
probe
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. 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), lift
the panel and remove it.
A
Fig. 2
To remove the side panels loosen the screws Band C
(Fig. 3), bring the base of the panels away from the
boiler and lift them, freeing them from the top hooks.
B
D
C
Fig. 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. 3).
3RemovethescrewsD
4 Move the lower part of the side panels as indi-
cated in Fig. 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. 4
5RemovethescrewsEand remove the service
panel (Fig. 5);
6 To gain access to the electronic regulation PCB
remove the screws Fand remove the control pan-
el lid (Fig. 5);
E
F
F
Fig. 5
2.4 Access to the sealed chamber
G
G
Fig. 6
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 Gas indicated in Fig. 6
and remove the lid.
2.5 Emptying the primary circuit
1 Close the c.h. circuit flow and return cocks H.
(Fig. 7).
H
H
J
Fig. 7 --- bottom view of the boiler
2 Remove the front and right panels of the boiler.
3 Open the drain tap I(Fig. 8) until the boiler is com-
pletely emptied.
4 Close drain tap again once the emptying has
been completed.
I
Fig. 8
2.6 Emptying the d.h.w. circuit
5 Close the d.c.w. inlet cock J(Fig. 7);
6 Open one or more hot water taps until the boiler
has been completely emptied.

4
3Diagrams
3.1 Wiring diagram
1
23
L N
gnye bubn
bnbkbu
bn bubn bk bu
bu
bn gnye
M
~
rd bk wh
3
2
1
bn buwh rd bk
bn bu
bn
bu
M
~
bu bn gnye
bk
bk
t
wh
wh
tbu
bu
bu
wh
trd
rd
bk
bk
Time switch
rd
bk
wh
gn
Ignition
electrodes Flame detection
electrode
External controls
terminal block
Electric supply
terminal block
Three way
diverter valve
Pump Fan
M
~
Primary circuit
pressure switch
Air pressure
sensor
D.h.w. flow
switch
C.h. temperature
probe NTC
Modulating
gas valve
Safety
thermostat
Flue
probe NTC
D.h.w. temperature
probe NTC
ye
gy
bn = brown
bu = blue
bk = black
wh = white
rd = red
gy = grey
gn = green
ye = yellow
vt = violet
og = orange
gnye = green/yellow
bubn gnye
bu
bubk
bu bu
bn
bu
bk wh wh
rd
rd
gn
wh
bk
rd
P
rd
ye
gy
rd
gy
ye
gy
gy
bk
bk
ye
gy
rd
rd
wh
bu
1
2
3
gnye
1
3
4
bu
bu
*bk *bn *bu
* = alternative

Diagrams
5
3.2 Functional flow diagrams
PTCJ 1 --- 1
L
General layout
Tra nsfo rme r
N
Electronic
control p.c.b.
(low voltage section)
J 1 --- 2
J 3 --- 3
J 3 --- 5
J 3 --- 4
J 3 --- 2J 3 --- 1
J 2 --- 4J 2 --- 5
Three way
diverter valve
Pump
Full sequence
ignition device
Fuse 3,15 A
PTCJ 1 --- 1
L
Tra nsfo rme r
ACTIVE CIRCUIT
INACTIVE CIRCUIT
L --- L IN E N --- N E U T R A L
N
Electronic
control p.c.b.
(low voltage section)
J 1 --- 2
J 3 --- 3
J 3 --- 5
J 3 --- 4
J 3 --- 2J 3 --- 1
J 2 --- 4J 2 --- 5
Three way
diverter valve
Pump
Full sequence
ignition device
Fuse 3,15 A
Heat request on d.h.w.
PTCJ 1 --- 1
L
Tra nsfo rme r
N
Electronic
control p.c.b.
(low voltage section)
J 1 --- 2
J 3 --- 3
J 3 --- 5
J 3 --- 4
J 3 --- 2J 3 --- 1
J 2 --- 4J 2 --- 5
Three way
diverter valve
Pump
Full sequence
ignition device
Fuse 3,15 A
Heat request on c.h.

Diagrams
6
3.3 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
Supply network
230~
230~
0
230~
230~
0
Pump
3way
230~
Modulating
Gas valve
diverter valve
Safety
thermostat
0
Fan
230~
+12 V DC
Air
sensor
pressure
0,5 ± 4,5 V DC

7
4Fault finding
Components to check
Section of the manual ! (note ref. in brackets)
---
(1)
---
(2)
---
(3)
21.1 ---
(4)
78.2 9.2 10.10 11.4 12.2 14.5 15.2 16 17.2 18.2 19.2 20.1 ---
(7)
---
(8)
--- ---
L o c k --- o u t s i g n a l l a m p r e d
Defect #
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 (on---off operators)
Gas valve (modulating operator)
Main circuit pressure 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 pressure sensor
Ignition electrode
Detection electrode
Safety thermostat
Flue probe NTC
Injectors
Expansion vessel
Safety valve
Pressure gauge
By pressing the reset push---button the boiler turns on and operates cor- rectly.
J J
(6)
J J J
By pressing the reset push---button the boiler starts the ignition cycle. The burner doesn’t light on, the igni-
tion sparks continue and the boiler locks again.
J J J J J
ON
By pressing the reset push---button the boiler starts the ignition cycle. The burner lights on, the ignition sparks continue and the boiler locks again.
J 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
The burner doesn’t light either in c.h. or d.h.w. mode. Fan turns.
J 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 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

8
Components to check
Section of the manual ! (note ref. in brackets)
---------
(8)
---
(7)
20.119.218.217.21615.214.512.211.410.109.28.27---
(4)
21.1---
(3)
---
(2)
---
(1)
L o c k --- o u t s i g n a l l a m p r e d
Pressure gauge
Safety valve
Expansion vessel
Injectors
Flue probe NTC
Safety thermostat
Detection electrode
Ignition electrode
Air pressure sensor
Fan
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 pressure switch
Gas valve (modulating operator)
Gas valve (on---off operators)
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
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 75°Candthec/h
system does not heat. The boiler operates correctly on d.h.w. mode.
J J
Incorrect modulation J J J Noisy bolier J J The boiler operates correctly but the gas pressure to the burner remains at minimum.
J J
F
Poor d.h.w. temperature J J J J J
(9)
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
---
Water leaks from the safety valve when the boiler is off.
J J J
Note Useful information can be obtained also from the optical indication given by the appliance oper- ation lights (see section 10.4). 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 tightness of the gas supply pipe, the position of stop
valves.
Check the gas pressure at the inlet test point of the gas valve (see sect. 11.3) with the boiler at rest and during operation and compare it with the values given on the installation booklet.
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.
6Checktheminimum gas pressure at the outlet test point of the
gas valve (see sect. 11.3) and compare it with the value given on the installation booklet.
7 Verify the cleanness of injectors. 8 Check the pressurization of the expansion vessel. Refer to the
installation manual for proper values.
9 d.h.w. pressure too high or flow rate too high. If necessary in-
sert a flow rate limiter (14.6)

9
5Primary heat exchanger
5.1 Function
The primary heat exchanger Ain Fig. 1 has the function
of transferring heat produced from combustion of the
gas to the water circulating in it.
A
Fig. 1
The hydraulic circuit is composed of 8 elliptical pipes
connected in parallel (Fig. 2).
Fig. 2
5.2 Removal
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1 Remove the case panels and the sealed chamber
lid (see section 2).
2 Empty the primary circuit of the boiler.
3 Remove the combustion chamber lid Bby un-
screwing the screws C(Fig. 3).
4RemovethescrewsDand the plate E.
5RemovetheclipF
6 Loosen the connection Gand slightly move the
pipe Hupwards.
7RemovetheclipIand the safety thermostat Jand
the c.h. temperature probe K. It is not necessary
to disconnect it from the wiring.
D
N
C
B
E
C
G
I
J
L
M
H
P
K
F
O
Fig. 3
8 Loosen the connection Land move the pipe M
downwards freeing it from the connection of the
primary het exchanger.
9RemovetheclipN
10 Loosen the connection O
11 free the pipe Pfrom the connection of the con-
densing heat exchanger; lift and and rotate it to-
wards right.
12 Remove the heat exchanger by sliding it for-
wards.
13 Reassemble the boiler carrying out the removal
operations in reverse order. Fit the clip Iwith the
arrow pointing upwards as illustrated in Fig. 3.
IMPORTANT -- do not force the connection Gwhen
tighting it.
5.3 Cleaning
If there are deposits of soot or dirt between the blades
of the heat exchanger, clean with a brush or non---me-
tallic bristle brush.

Primary heat exchanger
10
In any case, avoid any actions that can damage the pro-
tective varnish with which the exchanger has been cov-
ered.
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
6Condensing heat exchanger
6.1 Function
The return water flows through the condensing heat ex-
changer Ain Fig. 1 and Fig. 2.
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.
A
B
C
Fig. 1
6.2 Removal
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1 Remove the case panels and the sealed chamber
lid (see section 2).
2 Empty the primary circuit of the boiler.
3RemovethefanDin Fig. 2 (see section 17.3).
4 Disconect the connectors of the flue temperature
probe NTC E
5RemovetheclipF.
6 Completely loosen the connection Gand slightly
move the pipe Hupwards.
7RemovetheclipI.
8 Loosen the connection J
9 Free the pipe Kfrom the connection of the con-
densing heat exchanger; lift and and rotate it to-
wards right.
10 Using pliers, remove the spring Lmoving it to
wards right and disconnect the rubber pipe M.
11 Rotate the exchanger as indicated by the arrow
and remove it towards the front of the boiler.
D
E
G
I
L
M
J
A
K
F
H
Fig. 2
12 Reassemble the exchanger carrying out the re-
moval operations in reverse order.
Warning: to lubricate the O-- ring gaskets
exclusively use a silicone base grease
compatible to be in contact with foods and
approved by the local water Authorities.
After reassembling ensure that the fan -- exchanger
and exchanger-- elbow gaskets are correctly
mounted and ensure a good sealing.
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.
6.3 Cleaning
1 Using pliers, remove the spring Lmoving it to
wards right and disconnect the rubber pipe M
(Fig. 3).
2 Unscrewing the screws N(Fig. 3).
3 Remove the condensing heat exchange lid O
(Fig. 3) moving torwards the front of the boiler.
If there are deposits of soot or dirt on the exchanger lid,
cleanwithabrushornon---metallicbristlebrush.

Condensing heat exchanger
12
In any case, avoid any actions that can damage the pro-
tective varnish with which the lid has been covered.
L
M
N
O
Fig. 3
4 Reassemble the exchanger carrying out the re-
moval operations in reverse order.
Warning: to lubricate the O-- ring gaskets
exclusively use a silicone base grease
compatible to be in contact with foods and
approved by the local water Authorities.
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.

13
7D.h.w. heat exchanger
7.1 Function
The d.h.w heat exchanger Ain Fig. 1 and Fig. 4 allows
the instantaneous transfer of heat from the primary hy-
draulic circuit to the water destined for d.h.w use.
A
Fig. 1
The schematic structure is shown in Fig. 2.
Primary hydraulic circuit
Domestic hot water circuit
Fig. 2
7.2 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.
3RemovethepumpBin Fig. 3 (see section 8.3).
4RemovetheclipCand remove the primary circuit
pressure switch Dby lifting it upwards. It is not
necessary to disconnect it from the wiring.
5RemovetheclipEand remove the electric actua-
tor Fby pulling it. It is not necessary to disconnect
it from the wiring.
D
C
B
E
F
Fig. 3
6 Completely unscrew the two Allen key screws G
(Fig. 4) which hold the exchanger to the plastic
groups.
G
A
Fig. 4
7 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.
Warning: to lubricate the O-- ring gaskets
exclusively use a silicone base grease
compatible to be in contact with foods and
approved by the local water Authorities.
Attention. When reassembling the exchanger be
sure to put the off center location/securing pin indi-
cated in Fig. 5 towards the left side of the boiler.
Fig. 5

14
8Pump
8.1 Function
The pump Ain Fig. 1 and Fig. 3 has the function of mak-
ing the water in the main circuit circulate through the
main heat exchanger, the 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. 1
8.2 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. 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.
8.3 Removal
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1 Remove the case panels and the sealed chamber
lid (see section 2).
2 Empty the primary circuit of the boiler.
3 Extract and lower the control panel.
4RemovetheclipC(Fig. 2).
5 Loosen the connection D(Fig. 2).
6 free the pipe E(Fig. 2) from the connection of the
condensing heat exchanger; lift and and rotate it
towards right.
C
E
D
Fig. 2
7 Disconnect the connector B (Fig. 3).

Pump
15
B
F
G
A
Fig. 3
8 Remove the locking plate F(Fig. 3).
9 Unscrew the two screws Gthat hold the pump on
theframeandremovethepump.
Warning: to lubricate the O-- ring gaskets
exclusively use a silicone base grease
compatible to be in contact with foods and
approved by the local water Authorities.
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 return water group.

16
9Three way diverter valve
9.1 Function
The diverter valve A(Fig. 1) has the function of modify-
ing 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. 1
9.2 Checks
nCheck the electrical continuity
Fig. 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. 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.
Spindle B
visible
B
rd = red
wh = white
bk = black
230 V
0V
Open circuit
9,4 Kohm
w h --- * b k
r d --- * b n
b k --- * b u
3
1
2
bu = blue
bn = brown
* = alternative
F i g . 2 --- D . h . w . m o d e
rd = red
wh = white
bk = black
bu = blue
bn = brown
* = alternative
Spindle B
not visible
B
0V
230 V
Open circuit
9,4 Kohm
3
1
2
w h --- * b k
r d --- * b n
b k --- * b u
F i g . 3 --- C . h . m o d e
9.3 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. 4).
3 Remove the fixing spring Dand remove the
actuator B.
Reassemble the actuator carrying out the re-
moval operations in the reverse order.
When reassembling the actuator, refer to Fig. 2 or
to the wiring diagram in section 9.2 for the correct
wiring connection.

Three way diverter valve
17
C
D
B
Fig. 4
9.4 Removal of the tree way diverter valve
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 9.3).
4 Remove the fixing spring E(Fig. 5)
5 Remove the tree way diverter valve Fby levering
with a screwdriver in as shown in Fig. 5.
F
E
G
Fig. 5
Reassemble the tree way diverter valve carrying out the
removal operations in the reverse order.
Warning: to lubricate the O-- ring gaskets
exclusively use a silicone base grease
compatible to be in contact with foods and
approved by the local water Authorities.
Attention. When reassembling the tree way diverter
valvebesurethatthetreewaydiverteriscorrectly
oriented by matching the reference Gwith the notch
of the water group Fig. 5
9.5 Removal of the diverter group
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 9.3).
4 Remove the fixing spring H(Fig. 6) and remove
the primary circuit pressure switch I.
H
I
K
M
L
N
Fig. 6
5 Disconnect d.h.w. temperature probe, respect-
ively J(Fig. 7).
J
Fig. 7
6 Unscrew the connector K(Fig. 6), the c.h. flow
connector and the d.h.w. outlet connector.
7 Remove the d.h.w. heat exchanger (see section
7.2).
8RemovetheforkLand move away the pipe M
(Fig. 6).
9 Unscrew the screws Nand remove the diverter
group (Fig. 6).
10 Reassemble the diverter group carrying out the
removal operations in the reverse order.
Warning: to lubricate the O-- ring gaskets
exclusively use a silicone base grease
compatible to be in contact with foods and
approved by the local water Authorities.

18
10 Electronic control/ignition p.c.b.
10.1 Function
From other boiler devices....
C.h. temperature probe NTC
D.h.w. temperature probe NTC
D.h.w. flow switch
Primary circuit pressure switch
Air pressure sensor
Flue temperature probe NTC
Safety thermostat
Flame detection electrode
Room thermostat (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
On---off operators (gas valve)
Modulation operator (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. 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. 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, supplies the fan and
checks its functioning by means of the signal coming
from the air pressure sensor.
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).
fGas injectors blocked.
fFaulty modulation gas valve (faulty on---off oper-
ators or not electrically supplied).
fFaulty Electronic control/ignition p.c.b..
Other components like the air pressure sensor can tem-
porarily stop the ignition of the burner but allow its igni-
tion when the cause of the intervention has stopped.
Fig. 27 shows the sequence of the operations that are
carried out at the start of every ignition cycle and during
normal functioning.
10.2 Selection and adjustment devices
On the Electronic control/ignition p.c.b. several selec-
tion, adjustment and protection devices are located.
(Fig. 2).
Some of these devices are directly accessible by the
user (function control, temperature adjustment poten-