Biasi Parva HE M96.24SM/P User manual

Wall hung, fan flue, room sealed, high efficiency gas boiler
Service manual
Models: G.C. Appl. No.
M96.24SM/P 47---583---08
M96.28SM/P 47---583---09
M96.32SM/P 47---583---10
M96.28SR/P 41---583---05
M96.32SR/P 41---583---06
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
M96.24SM/... M96.28SM/... M96.32SM/... 4
3.2 Wiring diagram
M96.28SR/..., M96.32SR/... 5............
3.3 Functional flow diagrams 6..............
3.4 Circuit voltages 7......................
4Faultfinding 8........................
5 Primary heat exchanger 10..............
5.1 Function 10.............................
5.2 Removal 10............................
5.3 Cleaning 10............................
6 Condensing heat exchanger 11..........
6.1 Function 11.............................
6.2 Removal 11............................
7 D.h.w. heat exchanger 12...............
7.1 Function 12.............................
7.2 Removal 12............................
8Pump 13...............................
8.1 Function 13.............................
8.2 Checks 13.............................
8.3 Removal 13............................
9 Three way diverter valve 14.............
9.1 Function 14.............................
9.2 Checks 14.............................
9.3 Removal of the electric actuator 14........
9.4 Removal of the diverter group
and its internal parts 15..................
10 Electronic control/ignition p.c.b. 16......
10.1 Function 16.............................
10.2 Selection and adjustment devices 16......
10.3 Checking the temperature 17.............
10.4 Operation lights 18......................
10.5 Setting the boiler control function modes 18
10.6 Reignition frequency setting 19...........
10.7 Combi / C.H. only mode setting 19........
10.8 Ignition gas pressure adjustment 20.......
10.9 Checks 21.............................
10.10 Removal of the electronic control p.c.b 21..
10.11 Thermal control in the ” ”mode 23......
10.12 Thermal control in the ” ”mode 23......
10.13 Ignition and control sequence 24..........
11 Modulating 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 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 the temperature---pressure
gauge 28...............................
14 D.h.w. flow switch, filter 29.............
14.1 Function 29.............................
14.2 Description and location of parts 29.......
14.3 Checks 29.............................
14.4 Removal of the 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 31............................
16 By--pass valve 32......................
16.1 Function 32.............................
16.2 Removal 32............................
17 Fan, venturi device and
Air pressure switch 33..................
17.1 Function 33.............................
17.2 Checks 33.............................
17.3 Removal of the Fan 34...................
17.4 Inspection and removal of venturi device 34
17.5 Removal of the Air pressure switch 35.....
18 Ignition and detection electrodes 36.....
18.1 Function 36.............................
18.2 Checks 36.............................
18.3 Removal 36............................
19 Safety thermostat 37...................
19.1 Function 37.............................
19.2 Checks 37.............................
19.3 Removal 37............................
20 Flue temperature probe NTC 38.........
20.1 Function 38.............................
20.2 Checks 38.............................
20.3 Removal 38............................
21 Condensate trap 39
....................
21.1 Function 39.............................
21.2 Removal 39............................
22 Short spare parts list 40................

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
Air pressure
switch
Main circuit
Flue thermostat
heat exchanger
Condensate
trap
flow switch
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
45ûdownwards 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
M96.24SM/... M96.28SM/... M96.32SM/...
LD1LD2LD3
F1
F2
K1 K3 K4
LD4
P4
X6
X1
X7
P5
SB1
X5
K2
X3
X2
X4
123
LN M
~3
2
1
X11
M
~
t t
t
Time switch
rd
wh
gn
Ignition
electrodes Flame detection
electrode
Condensate
trap
External controls
terminal block
Electric supply
terminal block
Three way
diverter valve
Pump Fan
M
~
Primary circuit
flow switch
Air pressure
switch
D.h.w. flow
switch
C.h. temperature
probe NTC Modulating
gas valve
Safety
thermostat
Flue
temperature
D.h.w. temperature
probe NTC
bn = brown
bu = blue
bk = black
wh = white
rd = red
gy = grey
gn = green
ye = yellow
vt = violet
og = orange
gnye = green/yellow
Remote control
terminal block
probe NTC
bu
bn
gnye
bu bn bk
bn bu
bn bu bk
bu bn
gnye
bn bu bk bu bn bk bu bn
bu bk
gnye
bk bu
gnye
bk
bk
gy
gy
gy
gy
bn bu
bk
wh
wh
rd
bk
rd
rdwh
wh
bk
bk
bk
bk
bu
bn
gy*
gy
bu bu
bu
wh
X8
gy*
rd
rd
gy
wh
bu bu
bu bk
* alternative, yellow
bn bubu

Diagrams
5
3.2 Wiring diagram M96.28SR/...,
M96.32SR/...
LD1LD2LD3
F1
F2
K1 K3 K4
LD4
P4
X6
X1
X7
P5
SB1
X5
K2
X3
X2
X4
123
LN
X11
X8
M
~
t
t
Ignition
electrodes Flame detection
electrode
Condensate
trap
External controls
terminal block
Electric supply
terminal block
Pump Fan
M
~
Primary circuit
flow switch
Air pressure
switch
C.h. temperature
probe NTC Modulating
gas valve
Safety
thermostat
Flue
temperature
bn = brown
bu = blue
bk = black
wh = white
rd = red
gy = grey
gn = green
ye = yellow
vt = violet
og = orange
gnye = green/yellow
probe NTC
bu
bn
gnye
bu bn bk
bn bu
bu bn
gnye
bn bu bk bu bn
bu bk
gnyebk
bu
gnye
bk
bk
gy
gy
gy
gy
bn bu
gy* gy
bk
wh
wh
rd
wh
wh
bk
bk
bk
bk
bu
bn
gy*
gy
bu bu
bu
bu bk
* alternative, yellow
bn
bubu

Diagrams
6
3.3 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
7
3.4 Circuit voltages
LD1LD2LD3
F1
F2
K1 K3 K4
LD4
P4
X6
X1
X7
P5
SB1
X5
K2
X3
X2
X4
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~
0
Air
pressure
switch

8
4Fault finding
Components to check
Section of the manual ! (note ref. in brackets)
---
(1)
---
(2)
---
(3)
21.1 ---
(4)
78.2 9.2 10.9 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 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 and venturi device
Air pressure switch
Ignition electrode
Detection electrode
Safety thermostat
Flue thermostat
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
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

9
Components to check
Section of the manual ! (note ref. in brackets)
---------
(8)
---
(7)
20.119.218.217.21615.214.512.211.410.99.28.27---
(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 thermostat
Safety thermostat
Detection electrode
Ignition electrode
Air pressure switch
Fan and venturi device
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 (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)

10
5Primary heat exchanger
5.1 Function
The primary heat exchanger Ain Fig. 9 has the function
of transferring heat produced from combustion of the
gas to the water circulating in it.
A
Fig. 9
The hydraulic circuit is composed of 8 elliptical pipes
connected in parallel (Fig. 10).
Fig. 10
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 Cand removing the clamp
D(Fig. 11).
4RemovethescrewsEand the plate F.
5 Loosen the connection Gand slightly move the
pipe Hupwards.
6RemovetheclipIand the safety thermostat J.It
is not necessary to disconnect it from the wiring.
E
M
C
B
F
C
D
G
I
J
N
K
L
H
Fig. 11
7 Loosen the connection Kand move the pipe L
downwards freeing it from the connection of the
primary het exchanger.
8RemovetheclipM
9 Move the pipe Nupwards freeing it from the con-
nection and rotate towards right.
10 Remove the heat exchanger by sliding it for-
wards.
11 Reassemble the boiler carrying out the removal
operations in reverse order. Fit the clip Iwith the
arrow pointing upwards as illustrated in
Fig. 11.
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.
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. 12 and Fig. 13.
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. 12
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. 13 (see section 17.3)
and the air pressure switch E(see section 17.5).
4 Remove the flue temperature probe NTC F(see
section 20.3)
5 Completely loosen the connection Gand slightly
move the pipe Hupwards.
6RemovetheclipIand move the pipe Jdown-
wards freeing it from the connection, then turn it
towards right.
7 Using pliers, remove the spring Kmoving it down-
wards and disconnect the rubber pipe L.
8RemovethebracketMby unscrewing the screws
that hold it on the frame.
9 Rotate the exchanger as indicated by the arrow
and remove it towards the front of the boiler.
10 Remove the clip Nand the pipe H.
DD
E
F
G
I
K
L
M
A
J
N
H
Fig. 13
11 Reassemble the exchanger carrying out the re-
moval operations in reverse order.
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.

12
7D.h.w. heat exchanger
7.1 Function
The d.h.w heat exchanger Ain Fig. 14 and Fig. 16 al-
lows the instantaneous transfer of heat from the primary
hydraulic circuit to the water destined for d.h.w use.
A
Fig. 14
The schematic structure is shown in Fig. 15.
Primary hydraulic circuit
Domestic hot water circuit
Fig. 15
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.
3 Completely unscrew the two Allen key screws B
(Fig. 16) which hold the exchanger to the brass
groups.
B
A
Fig. 16
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 center location/securing pin indi-
cated in Fig. 17 towards the left side of the boiler.
Fig. 17

13
8Pump
8.1 Function
The pump Ain Fig. 18 and Fig. 19 has the function of
making the water in the main circuit circulate through
the main heat exchanger, the condensing heat ex-
changer and therefore through the c.h. system (during
the c.h. function) or through the secondary heat ex-
changer (during the d.h.w. function).
A
Fig. 18
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. 20).
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 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. 19).
5 Loosen the connection C, and pull up and turn to
the left the pipe D.
C
A
B
D
F
Fig. 19
6 Remove the locking plate E(Fig. 20).
7 Unscrew the two screws Fthat hold the pump on
theframeandremovethepump.
E
Fig. 20
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.

14
9Three way diverter valve
9.1 Function
The diverter valve A(Fig. 21) 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. 21
9.2 Checks
nCheck the electrical continuity
Fig. 22 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. 23 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
bn = brown
bu = blue
bk = black
0V
230 V
Spindle B
not visible
Open circuit
9,4 Kohm
bk bn bu
3
1
2
F i g . 2 2 --- D. h . w . m o d e
B
bn = brown
bu = blue
bk = black
230 V
0V
Spindle B
visible
Open circuit
9,4 Kohm
bk bn bu
3
1
2
F i g . 2 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. 24).
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. 22
or to the wiring diagram in section 9.2 for the cor-
rect wiring connection.

Three way diverter valve
15
CDE
Fig. 24
9.4 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 9.3).
4 Remove the fixing spring F(Fig. 25) and remove
the primary circuit flow switch G.
5 Disconnect both c.h. and d.h.w. temperature
probe, respectively Hand I.
6 Unscrew the connector J, the c.h. flow connector
and the d.h.w. outlet connector.
FG
J
H
I
Fig. 25
7 Remove the d.h.w. heat exchanger (see section
7.2).
8RemovetheforkKand move away the pipe L
(Fig. 26).
9 Unscrew the screw Mand remove the diverter
group.
K
L
M
Fig. 26 Rear view of the boiler
10 Refer to the exploded view in Fig. 27 to remove
the internal parts of the three way diverter valve.
Fig. 27
11 Reassemble the diverter group carrying out the
removal operations in the reverse order.

16
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 flow switch
Air pressure switch
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. 28
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. 28).
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 switch.
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.
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 switch can tem-
porarily stop the ignition of the burner but allow its igni-
tion when the cause of the intervention has stopped.
Fig. 52 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. 29).

Electronic control/ignition p.c.b.
17
Some of these devices are directly accessible by the
user (function control, temperature adjustment poten-
tiometers etc.) others are accessible by removing the
service panel or the control panel lid.
678910
11
123 4 5
Fig. 29
1 x1 connector
2 x6 connector
3 x7 connector
4 x4 connector
5 x2 connector
6 Lock ---out signal lamp
7 Boiler reset button
8 Function control / C.h. temperature adjustment
9 D.h.w. temperature adjustment
10 Appliance operation lights
11 Fuse 3,15 A F
10.3 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 (8 and
9 in Fig. 29) 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. 30), 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 modulation of the gas valve,
consequently changing the useful output of the boiler.
Fig. 30
When the boiler functions in d.h.w. (Fig. 31), the signal
coming from the d.h.w. temperature probe is compared
with the signal given by the control panel through the
adjustment made by the user (knob ).

Electronic control/ignition p.c.b.
18
75 ûC
Fig. 31
Normally, the result of the comparison between these
two signals directly operates the adjustment elements
of the gas valve modulation device, 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 75°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 10.11 and 10.12.
10.4 Operation lights
The Electronic control/ignition p.c.b. is provided with
three lamps (L.E.D. indicators) 10 in Fig. 29 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
lamp indication and its 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
(10 in Fig. 29) 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 primary circuit
(no water or absence of flow)
Faulty air pressure switch
Lack of burner ignition (no ignition signal from
the full seqence ignition device)
Safety thermostat lock out
Flue temperature probe NTC lock out
Lack of power supply or fauly 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.
10.5 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. 32).