biasi service manual

Wall hung, fan flue, room sealed gas boiler

SERVICE MANUAL

ParvaModels: G.C. Appl. No.

M90.24S 47--970--13M90.28S 47--970--14

Leave this manual adjacent to the gas meter

Biasi U.K. LtdUnit 32/33, Planetary Road

Industrial Estate, Neachells LaneWillenhall, Wolverhampton WV 13 3XB

Tel: 01902 304 400

Table of contents1 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. . . . . . . . . . . .3 Diagrams 4. . . . . . . . . . . . . . . . . . . . . . . . . . .3.1 Wiring diagram 4. . . . . . . . . . . . . . . . . . . . . . .3.2 Functional flow diagrams 5. . . . . . . . . . . . . .3.3 Circuit voltages 6. . . . . . . . . . . . . . . . . . . . . .4 Fault finding 7. . . . . . . . . . . . . . . . . . . . . . . .

5 Primary heat exchanger 9. . . . . . . . . . . . . .5.1 Characteristics 9. . . . . . . . . . . . . . . . . . . . . . .5.2 Removal 9. . . . . . . . . . . . . . . . . . . . . . . . . . . .5.3 Cleaning 9. . . . . . . . . . . . . . . . . . . . . . . . . . . .6 D.h.w. heat exchanger 10. . . . . . . . . . . . . . .6.1 Function 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . .6.2 Removal 10. . . . . . . . . . . . . . . . . . . . . . . . . . . .7 Pump 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7.1 Function 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . .7.2 Checks 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . .7.3 Removal 11. . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Three way diverter valve 12. . . . . . . . . . . . .8.1 Function 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . .8.2 Checks 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . .8.3 Removal of the electric actuator 12. . . . . . . .8.4 Removal of the diverter group

and its internal parts 13. . . . . . . . . . . . . . . . . .9 Electronic control p.c.b. 14. . . . . . . . . . . . . .9.1 Function 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . .9.2 Selection and adjustment devices 14. . . . . .9.3 Checking the temperature 14. . . . . . . . . . . . .9.4 Operation/Service lamps 15. . . . . . . . . . . . . .9.5 Dip---switch selectors 16. . . . . . . . . . . . . . . . .9.6 Ignition gas pressure adjustment 17. . . . . . .9.7 Max c.h. power adjustment 17. . . . . . . . . . . .9.8 Checks 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . .9.9 Removal of the electronic control p.c.b 17. .9.10 Thermal control in the ” ”mode 19. . . . . .9.11 Thermal control in the ” ”mode 19. . . . .

10 Full sequence ignition device 20. . . . . . . . .10.1 Function 20. . . . . . . . . . . . . . . . . . . . . . . . . . . . .10.2 Checks 20. . . . . . . . . . . . . . . . . . . . . . . . . . . . .10.3 Removal 20. . . . . . . . . . . . . . . . . . . . . . . . . . . .10.4 Ignition and control sequence 21. . . . . . . . . .11 Modulating gas valve 22. . . . . . . . . . . . . . . .11.1 Function 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . .11.2 Nomenclature of the parts 22. . . . . . . . . . . . .11.3 Adjustment 22. . . . . . . . . . . . . . . . . . . . . . . . . .11.4 Checks 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . .11.5 Removal 23. . . . . . . . . . . . . . . . . . . . . . . . . . . .12 Primary circuit flow switch 24. . . . . . . . . . .12.1 Function 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . .12.2 Checks 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . .12.3 Removal 24. . . . . . . . . . . . . . . . . . . . . . . . . . . .13 D.h.w. flow switch, filter and flow limiter 2613.1 Function 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . .13.2 Nomenclature and location of parts 26. . . . .13.3 Checks 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . .13.4 Removal of the flow switch sensor 26. . . . . .13.5 Removal of the flow switch group

and d.h.w. circuit filter 26. . . . . . . . . . . . . . . . .13.6 Flow limiter 27. . . . . . . . . . . . . . . . . . . . . . . . . .14 Temperature probe 28. . . . . . . . . . . . . . . . . .14.1 Function 28. . . . . . . . . . . . . . . . . . . . . . . . . . . . .14.2 Checks 28. . . . . . . . . . . . . . . . . . . . . . . . . . . . .14.3 Removal 28. . . . . . . . . . . . . . . . . . . . . . . . . . . .15 By--pass valve 29. . . . . . . . . . . . . . . . . . . . . .15.1 Function 29. . . . . . . . . . . . . . . . . . . . . . . . . . . . .15.2 Removal 29. . . . . . . . . . . . . . . . . . . . . . . . . . . .16 Fan and Air pressure switch 30. . . . . . . . . .16.1 Function 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . .16.2 Checks 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . .16.3 Removal of the Fan 30. . . . . . . . . . . . . . . . . . .16.4 Removal of the Air pressure switch 31. . . . .17 Ignition and detection electrodes 32. . . . .17.1 Function 32. . . . . . . . . . . . . . . . . . . . . . . . . . . . .17.2 Checks 32. . . . . . . . . . . . . . . . . . . . . . . . . . . . .17.3 Removal 32. . . . . . . . . . . . . . . . . . . . . . . . . . . .18 Safety thermostat 33. . . . . . . . . . . . . . . . . . .18.1 Function 33. . . . . . . . . . . . . . . . . . . . . . . . . . . . .18.2 Checks 33. . . . . . . . . . . . . . . . . . . . . . . . . . . . .18.3 Removal 33. . . . . . . . . . . . . . . . . . . . . . . . . . . .19 Short spare parts list 34. . . . . . . . . . . . . . . .

1

1 Overall information1.1 Overall View

Fan

Safetythermostat

Main heatexchanger

Burner

Ignitionelectrodes

Gas valve

Controlpanel

Combustionchamber

Automaticair release

Pump

D.h.w. temp.probe

D.h.w.heat exchanger

Expansionvessel

Detectionelectrode

valve

D.h.wflow switch

Diverter valve

Air pressureswitch

Main circuitflow switch

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

2 General access and emptyinghydraulic circuits

2.1 Nomenclature

2

6

1

5 4

3

Fig. 1

1 Right side panel2 Front panel3 Control panel lid4 Control panel cover5 Service panel6 Left side panel

2.2 Body panels

Warning: isolate the boiler from the mainselectricity supply before removing anycovering or component.

For the most part of the check and maintenance oper-ations it is necessary to remove one or more panels ofthe case.

The side panels can be removed only after the removalof the front panel.

To remove the front panel remove screws A (Fig. 2), liftthe panel and remove it.

A

Fig. 2

To remove the side panels loosen the screws B and C(Fig. 3), bring the base of the panels away from theboiler and lift them, freeing them from the top hooks.

B

D

D

C

C

Fig. 3 --- bottom view of the boiler

2.3 Control panelWarning: isolate the boiler from the mainselectricity supply before removing anycovering or component.

To gain access to the parts located inside the controlpanel proceed as follows:1 Remove the front panel of the case2 Loosen the screws B and C (Fig. 3).3 Remove the screws D4 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 rotate45° downwards to facilitate the service oper-ations on the internal parts.

General access and emptying hydraulic circuits

3

Fig. 45 Remove the screws E and remove the service

panel (Fig. 5);6 To gain access to the electronic regulation PCB

and the full sequence ignition device remove thescrews F and remove the control panel 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 sealedchamber it is necessary to remove the lid of the sealedchamber.For this purpose, remove the front and side panels ofthe case, remove the screws G as indicated in Fig. 6and remove the lid.

2.5 Emptying the primary circuit1 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. circuit5 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

3 Diagrams3.1 Wiring diagram

Ignitionelectrodes

Flame detectionelectrode

bn = brownbu = bluebk = blackwh = whiterd = redgy = grey

Safetythermostat

External controls Electric supply Fan Air pressureswitch

Time switch

123

tbk bk

t

bk

bkbk

M~

M~

bkbk

bk

bk

bkbk

bk

gy

M~

bk

bk

bkterminal blockterminal block

gy bk

Pump

Modulating

Primary circuitD.h.w. temperatureprobe NTC

Three waydiverter valve

gas valve

D.h.w. flowswitch flow switch

C.h. temperatureprobe NTC

Electroniccontrol p.c.b.

Full sequenceignition device

gn = greengnye = green---yellow

gnye gnyebnbu

gyrd

bu

wh rd

bu

rd

bubnbubn

bnbubnbu

bkbn bu31 2 bk gnyebu

rd

wh

bnbu

bubn

bubn

gnye

gnye

gnye

gnye

gnyegnye

gnye

gnye

gnye

gnye bu bn

bnbu

rd rd wh bu

rd bu

rd

rd gy

bn

bu

bububn

bugyrd

gnye

gy

wh gnye bnbu

bnbu

bk

rdbkwhgn

NC

COM

NO

Diagrams

5

3.2 Functional flow diagrams

PTCJ1---1

L

General layout

Transformer

N

Electroniccontrol p.c.b.(low voltage section)

J1---2

J3---3

J3---5J3---4

J3---2J3---1

J2---4J2---5


Pump


Fuse 1,6A T

PTCJ1---1

L

Transformer

ACTIVE CIRCUITINACTIVE CIRCUIT

L --- LINE N --- NEUTRAL

N


J1---2

J3---3

J3---5J3---4

J3---2J3---1

J2---4J2---5


Pump


Fuse 1,6A T

Heat request on d.h.w.

PTCJ1---1

L

Transformer

N


J1---2

J3---3

J3---5J3---4

J3---2J3---1

J2---4J2---5


Pump


Fuse 1,6A T

Heat request on c.h.

Diagrams

6

3.3 Circuit voltages

230~Supp

lyne

twor

k

230~

230~

0

Electrical voltages with burner on

during c.h. or d.h.w. operation

only during c.h. operation

only during d.h.w. operation

230~

230~

230~

0

Pump

Full sequenceIgnition device

3wa

ydi

verte

rvalv

e

0 0


230~ 230~

ModulatingGas valve

Safetythermostat

0

Fan

230~

230~

0


Airpressureswitch

7

4Fa

ultf

indi

ngCo

mpo

nent

sto

chec

kSe

ctio

nof

the

man

ual!

(not

ere

f.in

brac

kets)

--- (2)

--- (3)

--- (4)

--- (5)

67.

28.

29.

810

.211

.412

.213

.514

.215

16.2

17.2

18.2

--- (8)

--- (9)

------

Applianceoperationlampgreen(1)

Lock---outsignallampred

Defe

ct#

Powersupplyline

Gassupplyline

Fluepipes

C.h.circuit

D.h.w.circuit

D.h.w.heatexchanger

Pump

Divertervalve

D.h.w.flowswitch

Fuse(regulationp.c.b.)

Regulationp.c.b.

Functionselectors(reg.p.c.b)

Fullsequencedevice

Gasvalve(on---offoperators)

Gasvalve(modulatingoperator)

Maincircuitflowswitch

D.h.w.filter

Maincircuittemp.probe

D.h.w.temp.probe

By---passvalve

Fanandventuridevice

Airpressureswitch

Ignitionelectrode

Detectionelectrode

Safetythermostat

Injectors

Expansionvessel

Safetyvalve

Pressuregauge

OFF

OFF

The

boile

rdoe

snot

start

eithe

rin

c/h

ord.

h.w.

mod

e.Fa

nsti

ll.

JJ

J

Bypr

essin

gth

ere

setp

ush-

--but

ton

the

boile

rtur

nson

and

oper

ates

corre

ctly.

JJ (7

)J

JJ

ulses

Bypr

essin

gth

ere

setp

ush-

--but

ton

the

boile

rsta

rtsth

eig

nitio

ncy

cle.

The

burn

erdo

esn’

tlig

hton

,the

igni

-tio

nsp

arks

cont

inue

and

the

boile

rlo

cksa

gain

.

JJ

JJ

ON---fastpul

ON

Bypr

essin

gth

ere

setp

ush-

--but

ton

the

boile

rsta

rtsth

eig

nitio

ncy

cle.

The

burn

erlig

hts

on,t

heig

nitio

nsp

arks

cont

inue

and

the

boile

rloc

ksag

ain.

JJ

JJ

J

The

burn

erdo

esn’

tligh

teith

erin

c.h.

ord.

h.w.

mod

e.Fa

ntu

rn.

JJ

JJ

The

burn

erdo

esn’

tligh

teith

erin

c.h.

ord.

h.w.

mod

e.Fa

ndo

esn’

ttur

n.

JJ

JJ

JJ

JJ

stpulses

The

boile

rdoe

sn’t

cont

rolth

ed.

h.w.

tem

pera

ture

.Tu

rnin

gth

ed.

h.w.

tem

p.ad

justm

ent

knob

hasn

’tef

fect

onth

em

odul

atio

nof

the

flam

e.Th

ebo

ilero

pera

tesc

orre

ctly

onc.

h.

JJ

ON---fas

OFF

The

boile

rlig

htsf

ora

shor

twhi

leon

c.h.

Norm

alop

erat

ion

ond.

h.w.

func

tion.

JJ

8

Com

pone

ntst

och

eck

Sect

ion

ofth

em

anua

l!(n

ote

ref.

inbr

acke

ts)---

------ (9

)--- (8

)18

.217

.216

.215

14.2

13.5

12.2

11.4

10.2

9.8

8.2

7.2

6--- (5

)--- (4

)--- (3

)--- (2

)

Applianceoperationlampgreen(1)

Pressuregauge

Safetyvalve

Expansionvessel

Injectors

Safetythermostat

Detectionelectrode

Ignitionelectrode

Airpressureswitch

Fanandventuridevice

By---passvalve

D.h.w.temp.probe

Maincircuittemp.probe

D.h.w.filter

Maincircuitflowswitch

Gasvalve(modulatingoperator)

Gasvalve(on---offoperators)

Fullsequencedevice

Functionselectors(reg.p.c.b)

Regulationp.c.b.

Fuse(regulationp.c.b.)

D.h.w.flowswitch

Divertervalve

Pump

D.h.w.heatexchanger

D.h.w.circuit

C.h.circuit

Fluepipes

Gassupplyline

Powersupplyline

Defe

ct#

Lock---outsignallampred

The

boile

rdoe

snot

supp

lyd.

h.w.

(col

dwa

terf

rom

the

tap)

.Re

gular

oper

atio

nin

c/h

mod

eev

endu

ring

adr

awin

gof

fd.h

.w.

JJ

J

On

c/h

mod

eth

ete

mpe

ratu

reof

the

main

circu

itrea

ches

75°C

and

the

c/h

syste

mdo

esno

thea

t.Th

ebo

ilero

pera

tesc

orre

ctly

ond.

h.w.

mod

e.

JJ

Inco

rrect

mod

ulat

ion

JJ

J

s

Noisy

bolie

rJ

J

malpulses

The

boile

rope

rate

scor

rect

lybu

tthe

gasp

ress

ure

toth

ebu

rner

rem

ainsa

tm

inim

um.

JJ

---norm

F

Poor

d.h.

w.te

mpe

ratu

reJ

JJ

JJ (1

0)

ON--

OFF

Low

d.h.

w.flo

wra

teJ

JJ

------

Wat

erlea

ksfro

mth

esa

fety

valve

dur-

ing

oper

atio

non

c/h

JJ

JJ

------

Wat

erlea

ksfro

mth

esa

fety

valve

when

the

boile

riso

ff.J

JJ

Note

1Fo

rdet

ailss

eese

ctio

n9.

4of

this

man

ual.

Furth

erus

eful

info

rmat

ion

can

beob

tain

edby

switc

hing

the

elec

troni

ccon

trolp

.c.b

.inth

ese

rvic

eop

erat

ion

mod

e(s

eese

ctio

n9.

4of

this

man

ual).

2Ch

eck

for2

30V~

betw

een

line

(L)a

ndne

utra

l(N)

Verif

yth

ein

tegr

ityof

supp

lyca

ble,

plug

and

exte

rnal

fuse

s.Ch

eck

the

polar

ityof

line

and

neut

ralc

onne

ctio

n3

Verif

yth

eso

undn

ess

ofth

ega

ssu

pply

pipe

,the

posit

ion

of

stop

valve

s.Ch

eck

the

gasp

ress

ure

atth

ein

lette

stpo

into

fthe

gasv

alve

(see

sect

.11.

3)wi

thth

eboi

lerat

rest

and

durin

gop

erat

iona

ndco

mpa

reitw

ithth

eva

lues

give

non

the

insta

llatio

nbo

oklet

.

4Ch

eckf

orso

undn

essa

ndab

senc

eof

obstr

uctio

ns.V

erify

that

the

flue

term

inal

isco

rrect

lyin

stalle

d(s

eecle

aran

ces)

and

en-

sure

that

exha

ustg

asis

nots

ucke

dba

ckby

the

boile

r.

5Ch

eck

fors

ound

ness

ofth

ecir

cuita

ndve

rify

itsco

rrect

fillin

g(s

eeals

oin

stalla

tion

man

ual).

6A

jam

med

by---p

assc

ould

caus

ethe

over

---hea

ting

ofth

emain

circu

itand

the

inte

rven

tion

ofth

esa

fety

ther

mos

tat.

7Ch

eckt

hem

inim

umga

spre

ssur

eatth

eout

lette

stpo

into

fthe

gasv

alve

(see

sect

.11.

3)an

dco

mpa

reitw

ithth

eva

lue

give

non

the

insta

llatio

nbo

oklet

.8

Verif

yth

ecle

anne

ssof

inje

ctor

s.9

Chec

kthe

pres

suriz

atio

nof

thee

xpan

sion

vess

el.Re

fert

oth

ein

stalla

tion

man

ualfo

rpro

perv

alues

.10

d.h.

w.pr

essu

reto

ohi

ghor

flow

rate

too

high

.Ifne

cess

aryi

n-se

rta

flow

rate

limite

r(13

.6).

9

5 Primary heat exchanger5.1 Characteristics

The primary heat exchanger A in Fig. 9 has the functionof transferring heat produced from combustion of thegas to the water circulating in it.

A

Fig. 9

The hydraulic circuit is composed of 8 elliptical pipesconnected in parallel (Fig. 10).

Fig. 10

5.2 Removal


1 Empty the primary circuit of the boiler.2 Remove the case panels and the sealed chamber

lid (see section 2).3 Remove the combustion chamber lid B by un-

screwing the screws C (Fig. 11).3b For model M90.28S only, remove the screw D and

the plate E.4 Remove the clips F and the safety thermostat G.

It is not necessary to disconnect it from the wiring.

D

F

C

B E

G

Fig. 11

5 Remove the fork H (Fig. 12), lift the pipe I and ro-tate it right then move it downwards freeing it fromthe heat exchanger connection.

6 Remove the motor of the three way diverter valve(see section 8.3).

7 Loosen the two connection J and completely un-screw the connections K.

8 Rotate the pipe L and move the pipe M down-wards freeing it from the heat exchanger connec-tion.

9 Remove the heat exchanger by sliding it for-wards.

10 Reassemble the boiler carrying out the removaloperations in reverse order.

H

IJ

K

M

L

Fig. 12

5.3 CleaningIf there are deposits of soot or dirt between the bladesof 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.

10

6 D.h.w. heat exchanger6.1 Function

The d.h.w heat exchanger A in Fig. 13 allows the instan-taneous transfer of heat from the primary hydraulic cir-cuit to the water destined for d.h.w use.

A

Fig. 13

The schematic structure is shown in Fig. 14.

Primary hydraulic circuitDomestic hot water circuit

Fig. 14

6.2 RemovalWarning: isolate the boiler from the mainselectricity supply before removing anycovering or component.

1 Remove the front and right hand side panels ofthe case.

2 Empty the primary circuit and the d.h.w circuit ofthe boiler.

3 Remove the motor of the three way diverter valve(see section 8.3).

4 Completely unscrew the two connections B andremove the pipe C (Fig. 15).

B

C

Fig. 155 Completely unscrew the two Allen key screws D

(Fig. 16) which hold the exchanger to the brassgroups.

D

Fig. 166 Move the exchanger towards the rear of the boiler

and extract it.Reassemble the d.h.w. heat exchanger carrying out theremoval operations in the reverse order.Attention. When reassembling the exchanger besure to put the off center location/securing pin indi-cated in Fig. 17 towards the left side of the boiler.

Fig. 17

11

7 Pump7.1 Function

The pump A in Fig. 18 has the function of making thewater in the main circuit circulate through the main heatexchanger and therefore through the c.h. system (dur-ing the c.h. function) or through the secondary heat ex-changer (during the d.h.w. function).

A

Fig. 18

7.2 ChecksWarning: isolate the boiler from the mainselectricity supply before removing anycovering or component.

n Check that the pump is not seized and that themovement of the rotor is not subject to mechanical im-pediments.With the boiler off, remove the front panel. Remove theair release plug of the pump and turn the rotor with ascrewdriver.n Check the electrical continuity.With the boiler off, remove the front panel and discon-nect the connector B (Fig. 19).Measure the electrical resistance between the pumpsupply connections.Electrical resistance of the windings (at ambient tem-perature) must be about 230 Wn Check the absence of starting defects.With the boiler off remove the front case panel.Remove the air release plug from the pump. Start theboiler and with a screwdriver, turn the rotor in the direc-tion of the arrow. If there is a defect in starting, the rotorwill begin to turn normally only starting it manually.

n Check that the impeller is integral with the rotor.With the boiler off remove the front and right hand sidecase panels, lower the control panel and empty the pri-mary circuit.Remove the pump head by undoing the screws whichhold it to the pump body and check that the impeller isfirmly joined to the rotor.


1 Remove the front and right hand side case panels2 Empty the primary circuit of the boiler.3 Extract and lower the control panel.4 Disconnect the connector B (Fig. 19).5 Remove the fork C and move the pipe upwards

freeing it from the outlet port of the pump.6 Move the locking plate D left until it stops. It is not

necessary to extract it completely.7 Unscrew the two screws E that hold the pump on

the frame

D E

B

C

Fig. 198 Remove the fork F (Fig. 20), the capillary pipe and

remove the pump towards the front of the boiler.

F

Fig. 20

Reassemble the pump carrying out the removal oper-ations in the reverse order. When reassembling thepump, check the correct location of the O---ring gasketin the inlet port of the pump that seals the connectionbetween the pump and the brass group .

12

8 Three way diverter valve8.1 Function

The diverter valve A (Fig. 21) has the function of modify-ing the hydraulic circuit of the boiler by means of anelectric 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

8.2 Checksn Check the electrical continuityFig. 22 indicates the relationship between the electriccommand coming from the electronic control p.c.b.and the position of the actuator B (brass spindle) whenthe boiler operates on d.h.w. mode.Fig. 23 indicates the relationship between the electriccommand coming from the electronic control p.c.b.and the position of the actuator B (brass spindle) whenthe boiler operates on c.h. mode.In both figures the relationship between the position ofthe actuator and the resistance of the motor windings(the motor must be disconnected from the wiring) isalso given.

B

bn = brownbu = bluebk = black

0V

230

V

Spindle Bnot visible

Open circuit

9,4 Kohm

bk bnbu

3

1

2

Fig. 22 --- D.h.w. mode

B

bn = brownbu = bluebk = black

230

V0

V

Spindle Bvisible

Open circuit

9,4 Kohm

bk bnbu

3

1

2

Fig. 23 --- C.h. mode

8.3 Removal of the electric actuatorWarning: isolate the boiler from the mainselectricity supply before removing anycovering or component.

1 Remove the front case panel.2 Disconnect the connectors C (Fig. 24).3 Remove the fixing spring D and remove the

actuator E.Reassemble the actuator carrying out the re-moval operations in the reverse order.When reassembling the actuator, refer to Fig. 22or to the wiring diagram in section 3.1 for the cor-rect wiring connection.

Three way diverter valve

13

D

CE

Fig. 24

8.4 Removal of the diverter group and itsinternal parts

1 Remove the front and both side case panels.2 Empty the primary circuit and the d.h.w circuit of

the boiler.3 Remove the electric actuator (see section 8.3).4 Remove the fixing spring F (Fig. 25) and remove

the primary circuit flow switch G.5 Disconnect the c.h. temperature probe H.6 Unscrew the connector I, the c.h. flow connector

and the d.h.w. outlet connector.

F

G

I H

Fig. 25

7 Remove the d.h.w. heat exchanger (see section6.2).

8 Remove the fork J and move away the pipe K(Fig. 26).

9 Unscrew the screw L and remove the divertergroup.

J

K

L

Fig. 26 Rear view of the boiler10 Refer to the exploded view in Fig. 27 to remove

the internal parts of the three way diverter valve.

Fig. 2711 Reassemble the diverter group carrying out the

removal operations in the reverse order.

14

9 Electronic control p.c.b.9.1 Function

From other boiler devices....C.h. temperature probe NTCD.h.w. temperature probe NTCD.h.w. flow switchPrimary circuit flow switchRoom thermostat (if fitted)Time switchFlame presence signal**from the full sequence ignition device

On the Electronic control p.c.b.......Function control*C.h. temperature adjustment*D.h.w. temperature adjustment*Function dip---switchesMax. c.h. gas pressure adjustmentIgnition gas pressure adjustmentBoiler reset button**control panel fascia

Inlet Information

PumpThree way diverter valveFull sequence ignition deviceModulation operatorAppliance operation light*Operation/service lampsLock---out signal lamp**control panel fascia

Outlet command

Fig. 28

The fundamental function of the Electronic controlp.c.b. is that of controlling the boiler in relation to the ex-ternal needs (i.e. heating the dwelling or heating thewater for d.h.w. use) and operating in order to keep thetemperature of the hydraulic circuits constant.This is obviously possible within the useful power andmaximum working temperature limits foreseen.Generally, the Electronic control p.c.b. receives inlet in-formation coming from the boiler (the sensors) or fromthe outside (knobs, room thermostat, etc.), processesit and consequently acts with outlet commands onother components of the boiler (Fig. 28).9.2 Selection and adjustment devices

On the Electronic control p.c.b. several selection, ad-justment and protection devices are located. (Fig. 29).Some of these devices are directly accessible by theuser (function control, temperature adjustment poten-tiometers etc.) others are accessible by removing theservice panel or the control panel lid.

345678

9

11

12

14

10

1

2

13

Fig. 291 J3 connector2 J2 connector3 Lock---out signal lamp4 Boiler reset button5 Function control / C.h. temperature adjustment6 D.h.w. temperature adjustment7 Service lamps (service mode)8 Appliance operation lamp (normal use mode)9 Dip---switch selectors10 Setting jumpers11 Ignition gas pressure adjustment (ACC.)12 Maximum c.h. gas pressure adjustment (RISC.)13 J1 connector14 Fuse 1,6 A T

9.3 Checking the temperatureThe Electronic control p.c.b. makes it possible tosepar-ately 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.

Electronic control p.c.b.

15

The user, setting the desired temperature with the con-trol panel knobs operates the variable elements (5 and6 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 switchingOFF (ON/OFF function). If the power requested ishigher, then the burner is switched ON at maximumpower and will control by modulating to 40% of themaximum power output.During the c.h. operation (Fig. 30), the signal comingfrom the c.h. temperature probe is compared to the sig-nal given by the control panel through the adjustmentmade by the user (knob ). The result of such a com-parison 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 signalcoming from the d.h.w. temperature probe is comparedwith the signal given by the control panel through theadjustment made by the user (knob ).

75 ° C

Fig. 31

Normally, the result of the comparison between thesetwo signals directly operates the adjustment elementsof the gas valve modulation device, adjusting the usefuloutput generated in order to stabilize the temperatureof the exiting water.If during the d.h.w. mode operation, the temperature ofthe primary circuit goes over 75°C, the useful output isautomatically reduced so that the primary circuit can-not reach excessive temperatures.

The control sequences in function and in func-tion are illustrated in detail in sections 9.10 and 9.11.9.4 Operation/Service lamps

The Electronic control p.c.b. is provided with threelamps (L.E.D. indicators) 7 in Fig. 29 that give optical in-formation during the normal operation of the boiler orfor service purpose.f Normal operationOnly the green lamp on the left is directly visible on thecontrol panel fascia and it gives information during thenormal operation of the boiler. The other two lamps arenormally switched off.


16

The following table gives the relationship between thevisible lamp indication and its meaning.

Boiler in stand---by condition.(function control in position).Anti--- freeze system active.

A short pulse every 4 seconds

(function control in position).Anti--- freeze system active.

Boiler ON condition(function control in orposition)

1 second ON 1 second OFF

(function control in orposition)

Very fast pulses (4 per second)

Faulty boiler or irregularoperation as:--- Empty primary circuit--- No primary circuit flow--- Lack of burner ignition--- Lack of burner ignition--- Excessive temperature in

the primary circuit.--- Dip---switch 3 left in the OFF

position--- Faulty temperature probe

f Service operation

With the boiler switched ON ( or ), by movingand re---setting to its original position any of the functionselectors 9 (Fig. 29), the Electronic control p.c.b. goesinto service operation mode and all the lamps (7 inFig. 29) are then activated.To reset the Electronic control p.c.b. to the normal oper-ation it is necessary to turn the knob to the posi-tion or switch off the boiler for a short while at the fusedspur isolation switch.The following table gives the relationship between eachof the possible lamp combinations and their meaning.

Normally operating boiler

C.h. operation

D.h.w. operation

Frost protect operation

D.h.w. operationExcessive 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 flow)

Lack of burner ignition (no ignition signal fromthe full seqence ignition device)

Ignition gas pressure adjustment

Minimum gas pressure adjustment

LampOFF

LampON

Flashing lamp, aloneor simultaneously

with an other lamp.

Flashing lamp,alternate withanother lamp.

9.5 Dip---switch selectorsThe function selectors 9 (Fig. 29 and Fig. 32) are micro-switches with which it is possible to select the variousboiler control function modes.In Fig. 32 the selectors are illustrated in the configur-ation in which the boiler is set in the factory (natural gasboiler).

ON (1)

OFF (0)

1 2 3 4

9

Gas conversionIgnition gas pressure adjustmentReignition frequency

Minimum gas pressure adjustment

Fig. 32f Selector 1This forces the boiler to operate at the minimum gaspressure in order to allow the adjustment of the mini-mum gas pressure at the burner (on the modulation op-erator of the gas valve).After any adjustment operation the selector has to bebrought back to the normal position (ON).


17

f Selector 2This selects the boiler functions on the basis of the typeof gas used.It allows the selection of the maximum supply currentgiven to the modulator device.To set selector 2 correctly follow the table in Fig. 33.

Gas supply Position of selector Approx. Max currentthrough the modu-lator device

Natural gas On 120 mAL.P.G. Off 165 mA

Fig. 33

f Selector 3This forces the functioning of the boiler in order to allowthe optimal gas pressure at the burner to be adjustedduring the ignition phase.The adjustment (see section 9.6) is done by means ofthe potentiometer ”11”marked “ACC”(Fig. 29 on page14).After the adjustment operations bring the selector backto the normal position (ON).

gas pressure calibration Normal

ON (1)

OFF (0)

Fig. 34

f Selector 4This allows you to select the minimum time that mustpass between two ignitions of the burner in c.h. func-tion.

30 sec. 3 min.

ON (1)

OFF (0)

Fig. 35

9.6 Ignition gas pressure adjustment

By using the device ”11”(Fig. 29) marked “ACC.”onthe Electronic control p.c.b., it is possible to adjust thegas pressure at the injectors in the ignition phase.This pressure is maintained at the injectors until ignitionoccurs (ionization signal from the full sequence ignitiondevice).To carry out the adjustment move the function selector3 to the OFF position (Fig. 34) and use the adjustmentdevice ”11”(ACC).Adjust the gas pressure at the injectors to the value indi-cated in the tables of the User/Installation manual

(Technical information section, Gas pressures at theburner table).By rotating the device clockwise the pressure in-creases.Check the regular ignition of the burner by turning theboiler on and off repeatedly.After the adjustment operations bring the selector 3back to the normal position (ON).

9.7 Max c.h. power adjustmentBy using device 12 (Fig. 29) marked “RISC.”on theElectronic control p.c.b., you can limit the maximumuseful output delivered during the c.h. operating mode.This adjustment does not influence the maximum use-ful output delivered during the d.h.w. operating mode.By rotating the device clockwise the pressure in-creases.

9.8 Checksn Check that the fuse is completeIf the Electronic control p.c.b. does not supply any de-vice (pump, fan, etc.) check that the fuse 14 (Fig. 29) iscomplete.If the fuse has blown replace it with one that has thesame characteristics after having identified the reasonfor failure.n Check the setting jumpers positionTwo setting jumpers must be fitted on the Electroniccontrol p.c.b. as shown in Fig. 36.The numbers refer to the marking printed on the circuitboard.

1 2 3 4 5 6 7 8 9Fig. 36

9.9 Removal of the electronic control p.c.b


1 Gain access to the parts located inside the con-trol panel as explained in the section 2.3 of thismanual.

2 Remove all the wiring connected to the Electroniccontrol p.c.b..To disconnect the connectors J1, J2 and J3 (13,2 and 1 in Fig. 29) delicately flex the hook presenton one side of each socket.

3 Remove the spindles of the c.h. and d.h.w. tem-perature adjustment knobs by delicately pullingthem with pliers in the direction shown by thearrow in Fig. 37.


18

Fig. 37

4 Unscrew the four screws that hold the Electroniccontrol p.c.b. on to the control panel.

5 Remove it by lifting its rear edge and freeing itfrom any of the wiring.

6 Re---assemble the Electronic control p.c.b. fol-lowing the removal procedures in the reverseorder.

ImportantWhen re---assembling the Electronic control p.c.b.:7 Fit the p.c.b. into the control panel by first insert-

ing the front lower edge under the control knobshafts. Lower the rear edge and ensure that nowiring is trapped beneath.

8 Insert the spindles in the control panel knobs un-till the notch A (Fig. 38) reaches the potentio-meter edge. It is not necessary to force them inthe knob.

9 While tightening the screws that fix the Electroniccontrol p.c.b. on the control panel, keep thep.c.b. towards the control panel fascia makingsure of the contact between the boiler reset but-ton B and the tab C (Fig. 38).

A B C

Fig. 38

AttentionAfter installing the Electronic control p.c.b. :

10 Make sure the c.h. ( ) and d.h.w. ( ) tem-perature adjustment knobs can move freely forthe complete range.If not, remove the spindle again as described atstep 3, turn the knob half a turn and re--- insert thespindle.

11 Operate the boiler and close the gas inlet cock sothat the boiler goes into the safety lock---out state.Verify the correct operation of the boiler reset but-ton by pressing and releasing it.


19

9.10 Thermal control in the ” ”mode

See functioning with the functioncontrol in the mode

(sec. 9.11)

Takingwater from the domestic hot

water circuit?

Switch in the function mode

NOYES

Is primary circuittemperature higher than that

selected?NO

Request for heat fromroom thermostat?

Starts the circulatorOperates motorised valve

Supplies the ignition device

NO

Circulator offOperates motorised valve

Ignition device off

YES

YES

Fig. 39

9.11 Thermal control in the ” ”mode

Is domestichot water outlet temperature

lower than thatrequired?

Supplies the ignition device Ignition device off

Circulator on

YES NO

Switch in the function mode

Takingwater from the domestic hot

water circuit?YES Circulator off

Ignition device offNO

Fig. 40

20

10 Full sequence ignition device10.1 Function

The Full sequence ignition device used on the boilercarries out the following fundamental functions:f does a sequence of operations (ignition cycle)

which lead to the ignition of the gas at the burnerf checks the presence of the flame during the en-

tire period in which it is activatedf supplies the fan and checks its functioning by

means of the signal coming from the air pressureswitch.

The Full sequence ignition device is supplied by theelectronic control p.c.b. when the ignition of the burneris requested.The Full sequence ignition device has a safety functionand any incorrect interventions or tampering can resultin conditions of dangerous functioning of the boiler.The Full sequence ignition device can lock the function-ing of the boiler (lock state) and stop its functioning upto the resetting intervention. The lock is signalled by thelighting of the lock---out signal lamp and the device canbe reset only by using the boiler reset button placed onthe control panel fascia.Some components which are connected to the devicecan activate the lock state. The causes of a lock statecould be:f The intervention of the safety thermostat (over-

heat of the primary circuit).f A fault on gas feedingf Faulty ignition (faulty ignition electrodes, their wir-

ing or connection).f Faulty flame detection (faulty detection electrode,

its wiring or connection).f Gas injectors blockedf Faulty modulation gas valve (faulty on---off oper-

ators or not electrically supplied).f Faulty Full sequence ignition device.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. 42 shows the sequence of the operations that arecarried out at the starting of every ignition cycle andduring normal functioning.

10.2 Checksn Lock sequenceStart the boiler until the burner is ignited.

With the burner firing, interrupt the gas supply. The Fullsequence ignition device must carry out a completeignition cycle and then stop.By turning the boiler on and off by means of the functionswitch the device must not unlock and the burner mustnot turn on.n Control of flue gas expulsionWith the boiler operating and the burner on, open thenegative pressure test point of the Venturi device.At the moment of opening the burner must turn off.

10.3 Removal


1 Gain access to the parts located inside the con-trol panel as explained in the section 2.3 of thismanual.

2 Remove all the wiring connected to the Full se-quence ignition device.To disconnect the connectors A, delicately flex thehook present on one side of each socket(Fig. 41).

3 Unscrew the two screws B that hold the Full se-quence ignition device on the panel and removethe component.

A

A

B

B

Fig. 41

4 Re---assemble the Full sequence ignition devicefollowing the removal procedures in the reverseorder.

Full sequence ignition device

21

10.4 Ignition and control sequence

lock memorised?

supply from the electronic control circuit

Air pressure switch atrest?

NO

NO

starts fan

YES

Air pressure switch atwork?

NO

beginning of wait period

presence of flame?NO YES

YES


NO

YES

starts ignition dischargesopens gas valve

beginning of ignition period

flame presence?

end of ignitionperiod?NO

NO YES

closes gas valvestops fan

interrupts ignition dischargesmemorizes lock

turns on lock---out light

YES

reset push---buttonpressed?

NO YES

cancels lock

interrupts ignition dischargesgas valve open

flame presence?


NO

YES

YES

closes gas valve

NO

YES

Safety thermostatopens the circuit?NO YES

Fig. 42

22

11 Modulating gas valve

11.1 Function

The Modulating gas valve A in Fig. 43 controls the gasinflow to the boiler burner.

A

Fig. 43

By means of an electric command given to the on---offoperators the passage of the gas through the Modula-ting gas valve can be opened or closed.

By means of an electric command given to the modula-tion operator the pressure can be varied and thereforethe gas flow rate to the burner (modulation). The mo-dulation operator has mechanical components whichallow the adjustment of the minimum and maximumpressure exiting the valve.

11.2 Nomenclature of the parts (Fig. 44)

1 Modulation operator’s electric connectors2 Minimum gas pressure adjustment3 On---off operators4 Maximum gas pressure adjustment5 On---off operators electric connector6 Gas valve inlet pressure test point7 Modulation operator8 Gas valve outlet pressure test point

3

7

1

6

8

5

2

4

Fig. 44

11.3 Adjustment


1 Remove the front panel of the case.2 Open the gas valve inlet pressure test point (6 in

Fig. 44) at the valve input, connect a suitablepressure gauge and check the gas pressure ofthe supply network.

3 Remove the gauge and close the pressure testpoint 6.

4 Open the gas valve outlet pressure test point (8in Fig. 44) and connect the gauge;

5 Remove the protection cap from the mechanicalpressure adjustment components;

6 Start the boiler at its maximum power.Operate the boiler in d.h.w. mode or ensure thatthe boiler is not range rated if the test is carried outin c.h. mode.

7 Rotate the maximum gas pressure adjustment (4in Fig. 44) until you obtain the required pressure(by rotating clockwise the pressure increases).

8 Disconnect one of the two connectors (1 inFig. 44) or, alternatively, remove the service panelas explained in the section 2.3 of this manual andset the dip---switch selector 1 (see section 9.5) tothe OFF position.

9 Rotate the minimum gas pressure adjustment (2in Fig. 44) until you obtain the required pressure(by rotating clockwise the pressure increases).

10 Turn the boiler off and re---connect the wire to themodulating operator (or set the dip---switch se-lector 1 back to the ON position).

11 Start the boiler and check again the maximumgas pressure setting.

12 Turn the boiler off and disconnect the gauge.Important: after the gas pressure checks and anyadjustment operations, all of the test points must besealed.

Modulating gas valve

23


n Check the modulation operator coil1 Remove the front panel of the case.2 Disconnect the connectors B (Fig. 46) from the

modulating operator and measure the electricalresistance of the coil. Its electrical resistancevalue must be approx. 80 W*.

n Check the on---off operators coils1 Remove the front panel of the case.2 Disconnect the electrical connector C (Fig. 46).3 Measure the electrical resistance between the

connector pins of the on---off operators as illus-trated in Fig. 45.

Lower on---off operatorapprox. 920 W*

Upper on---off operatorapprox. 6 400 W*

* at ambient temperature.Fig. 45


1 Remove the front panel of the case as explainedin the section 2.3 of this manual.

2 Disconnect the connectors B and C (Fig. 46).3 Turn off the gas supply and disconnect the gas

isolation cock connector from the inlet port of thegas valve.

4 Unscrew the connectors D and remove the pipeE

5 Unscrew the screws F and remove the valve.6 Reassemble the valve carrying out the removal

operations in reverse order.After any service operation on the components ofthe gas circuit check all the connections for gasleaks.

B

C

D

E

F

Fig. 46

24

12 Primary circuit flow switch12.1 Function

The Primary circuit flow switch (A in Fig. 47) function isto detect water flowrate through the primary hydrauliccircuit of the boiler.

A

Fig. 47

This hydraulic/membrane operated electrical micro---switch device will control the functioning of the ignitioncontrol circuit, providing there is an adequate quantityand flow of water in the primary circuit. Any failure of thepump or obstructions in the primary circuit, whilst ineither c.h. or d.h.w. modes, will not allow the device tooperate.This device is connected to the electronic control p.c.b.and if, after the pump operates, it does not activate with-in 20 seconds the control board will indicate that a faultcondition (see section 9.4 of this manual) has occurred.

D

C

Fig. 48


n Mechanical function1 Remove the front panel of the case.2 Start and stop the boiler either in d.h.w. or c.h.

mode.3 Looking through the switch box verify the position

of the shaft B referring to Fig. 49.

BBoiler OFF Boiler ONFig. 49

n Electrical checkIt is possible to verify the general operation of the switchby measuring the electric resistance between the con-tacts C. and N.O. of the switch.1 Remove the switch as explained in section 12.3.2 Measure the electrical resistance between the

tabs marked C. and N.O. (Fig. 50).The contact must be normally open.

3 Operate the switch by hand and verify that thecontact is now closed.

N.O.

do not use

C

Fig. 50


n Removal of the switch1 Remove the front and right hand side panels of

the case.2 Remove the fork C (Fig. 48).3 Open the box and disconnect the switch.4 Re---assemble the parts proceeding in reverse

order of removal. Refer to Fig. 50 for the correctwiring connectors on the switch

n Removal of the membrane1 Remove the front and right hand side panels of

the case, turn off the flow and return isolationvalves and empty the primary circuit.

2 Remove the fork C that holds the micro---switchhousing D (Fig. 48).

3 Unscrew the four screws E (see Fig. 51) open thehydraulic operator and remove the membrane F.

Primary circuit flow switch

25

E

FG

H

Fig. 51

4 Reassemble the parts in reverse order of removal.When assembling the membrane, ensure that itsconcave side faces towards the actuator plate G andthe reference indicated aligns with the seat H (seeFig. 51).

26

13 D.h.w. flow switch, filter and flowlimiter

13.1 FunctionThe d.h.w. flow switch A in Fig. 52 is a device that gener-ates an electrical signal when hot water is drawn.

A

Fig. 52

When the flow rate through the d.h.w. circuit reachesabout 2,5 litres/min’, the float 4 (Fig. 54) is drawn to-wards the right.The resulting magnetic field of ring 3 increases and re-aches the flow switch sensor 1.The sensor generates an electrical signal that switchesthe boiler d.h.w operation ON.The state of the sensor is also indicated by means of thelamp B placed on the sensor body.

BC

Fig. 53

13.2 Nomenclature and location of parts(Fig. 54)

1 Flow switch sensor2 Plug3 Magnetic ring4 Float5 Spring6 Filter7 Body8 Spring seat9 Flow limiter (M90.28S optional accessory)10 Threaded ring

1

23

45

67

89

10

Fig. 54


n Flow switch sensor operation1 Remove the front panel of the case.2 Switch on the boiler and open a d.h.w. tap. The

lamp B (Fig. 53) placed on the sensor body isswitched on when the flow rate reaches about 2,5litres/min’.

13.4 Removal of the flow switch sensor


1 Remove the front panel of the case.2 Disconnect the connector C (Fig. 53) and remove

the sensor by pulling it towards the front of theboiler (the sensor is held in place by means of aspring).

13.5 Removal of the flow switch group andd.h.w. circuit filter


1 Remove the front panel of the case and empty thed.h.w. circuit.

D.h.w. flow switch, filter and flow limiter

27

2 Remove the flow switch sensor (see section13.4).

3 Remove the gas valve (see section 11.5).4 Unscrew the plug 2 (Fig. 54) and extract the flow

switch group.5 To remove the filter from the flow switch group

separate the body 7 from the plug 2 (Fig. 54) byunscrewing it.

6 Reassemble the parts following the removing se-quence in reverse order.

13.6 Flow limiter

The M90.24S model is factory fitted with a 10 litre/min.flow limiter.

If on the M90.28S model the flow rate of the d.h.w. cir-cuit is too high, it is possible to limit it by installing a flowlimiter. The following sizes are available:

Nominal flow rate (litres/min) Colour10 Yellow12 Brown

To install the flow limiter:1 Remove the flow switch group as explained in the

section 13.5.2 Unscrew the threaded ring 10 (Fig. 54) and re-

move it from the body 7.3 Install the flow limiter 9 putting its smaller diam-

eter side towards the threaded ring.4 Reassemble the group following the above se-

quence in reverse order.

28

14 Temperature probe14.1 Function

The Temperature probe has the function of convertingthe temperature of the water in the hydraulic circuitwhere it is installed into an electrical signal (resistance).The relation between temperature and electrical resis-tance is stated in Fig. 55.

500100015002000250030003500400045005000550060006500700075008000850090009500

100001050011000115001200012500

20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

W

° CFig. 55

On the boiler there are two Temperature probes. Oneon the output of the primary heat exchanger (c.h. Tem-perature probe) A in Fig. 56 and Fig. 57; one on itsinput, before the pump (d.h.w. Temperature probe) B inFig. 56 and Fig. 58.

A

c.h.flow

c.h.return

d.h.w.inlet

d.h.w.outlet

B

Fig. 56

14.2 Checksn Temperature---resistance relationship


Disconnect the cable from the Temperature probe.Measure the temperature of the brass group where theTemperature probe is located and check the electricalresistance according to the graph in Fig. 55.


Refer to Fig. 57 for the c.h. Temperature probeand to Fig. 58 for the d.h.w. Temperature probe.

1 To remove the Temperature probes remove thefront and right hand side panels of the case.

2 Empty the primary circuit of the boiler.3 Remove the electric connector of the Tempera-

ture probe and unscrew it.4 Reassemble the Temperature probe carrying out

the removal operations in reverse order.

A

Fig. 57

B

Fig. 58

29

15 By---pass valve15.1 Function

The By---pass valve A in Fig. 59 is located between thec.h. water flow and return and its function is that of guar-anteeing a minimum flow across the primary heat ex-changer if the circulation across the c.h. system is com-pletely closed.The By---pass valve is fitted on the rear side of the div-erter group.

A

Fig. 59

15.2 Removal


1 Remove all the case panels.2 Empty the primary circuit of the boiler.3 Remove the diverter group as described in the

section 8.4 of this manual.4 Unscrew the connector B and remove the by---

pass valve C (Fig. 60).

C

B

Fig. 60

5 Reassemble the by---pass valve as illustrated inFig. 60 reversing the order of removal.

30

16 Fan and Air pressure switch16.1 Function

The function of the Fan is to force the products of com-bustion to the outside air via the flue system.The Fan is supplied by the full sequence ignition deviceat the beginning of the ignition cycle.Its correct functioning is controlled by means of a sys-tem incorporating a built in venturi device and an Airpressure switch.

16.2 Checksn Check of the fan


1 Remove all the case panels and the sealedchamber lid.

2 Disconnect the connectors A (Fig. 61) andmeasure the electrical resistance of the motorthat has to be about 32 W --- M90.24S and 30 W--- M90.28S (at ambient temperature).

A

B

G

Fig. 61

n Check of the Air pressure switch operation



2 Disconnect the wires and check the electrical re-sistance between the connections of the Air pres-sure switch (Fig. 62).

Between COM and N.O. the contact must be open.Between COM and N.C. the contact must be closed(electrical resistance zero).3 Connect the black wire (COM) and the brown

wire (N.C.).

4 Run the boiler (the Fan must run) and check thethe electric resistance between COM and N.O.

Between COM and N.O. the contact must beclosed (electrical resistance zero).

N.O.

N.C.

”L”connectionCOM

”H”connection

Fig. 62

16.3 Removal of the Fan


1 Remove all the case panels, the sealed chamberlid and the combustion chamber lid.

2 Disconnect the connectors A and the earth con-nection B (Fig. 61).

3 Disconnect the pipes which connect the venturidevice to the Air pressure switch.

4 Unscrew the screws C and remove the clamp D(Fig. 64).

4b For model M90.28S only, remove the screw E andthe plate F (Fig. 63).

E

F

Fig. 63

5 Unscrew the screws G (Fig. 61 and Fig. 64).andremove the flue hood with the Fan.

Fan and Air pressure switch

31

CD

G

Fig. 64

6 Remove the three screws securing the Fan to theflue hood.

7 Assemble the fan carrying out the removal oper-ations in reverse sequence.

Warning: to correctly connect the venturi device tothe Air pressure switch, refer to Fig. 65 for the modelM90.24S and to Fig. 66 for the model M90.28S.

--- +

Fig. 65

--- +

Fig. 66

16.4 Removal of the Air pressure switch



2 Disconnect the wires from the Air pressureswitch.

3 Remove the pipes from the Air pressure switch.4 Unscrew the screws which hold the Air pressure

switch to the frame.5 Assemble the Air pressure switch carrying out the

removal operations in reverse sequence.

Warning: to correctly connect the Air pressureswitch, refer to Fig. 65 for the model M90.24S, toFig. 66 for the model M90.28S and Fig. 62 for thecorrect wiring.

32

17 Ignition and detection electrodes17.1 Function

Three electrodes are fitted on the burner. Two of themare the ignition electrodes and are fitted near the frontpart of the burner. The ignition sparks take place be-tween their metallic edges over the central ramp of theburner during the ignition sequence.The third electrode is the detection electrode and it de-tects the presence of the flame.

Ignition

Detection

Male

Female

Fig. 67

17.2 Checksn Check the position of the electrode edges



2 Check for the correct distance between the me-tallic edges of the ignition electrodes (seeFig. 68).

Ignition

4 mm

Fig. 68

3 Check the integrity of the detection electrode andensure that its metallic edge is correctly placedover the ramp of the burner.

n Check the connection wires.



2 Check for the integrity of the insulation of wireswhich connect the electrodes to the ignition de-vice.

17.3 Removal



2 Disconnect the electrode wires from the full se-quence ignition device.

3 Remove the burner by unscrewing the fourscrews placed at the right and left sides of theburner.

3b For model M90.28S only, remove also the plate F(see Fig. 63 on page 30).

4 Unscrew the screws A (Fig. 69) which hold theelectrodes to the burner.

A

Fig. 69

5 Extract the electrodes from the burner.6 Assemble the electrodes carrying out the removal

operation in reverse order.Refer to Fig. 67 in order to recognize the elec-trodes and to correctly connect the wiring.

Note: the metallic edge of the detection electrode islonger than the one of the ignition electrodes.

33

18 Safety thermostat18.1 Function

The safety thermostat A in Fig. 70 is a device thatsenses the temperature of the primary circuit waterwhich flows in the outlet pipe of the primary heat ex-changer.If the temperature control system of the boiler fails andthe temperature of the primary circuit reaches a dan-gerous temperature, the safety thermostat opens theelectric circuit that supplies the on---off operators of thegas valve.Consequently, the full sequence ignition device at-tempts to light the burner and, at the end, locks theboiler and lights the lock---out signal lamp.

A

Fig. 70


n Overheat temperature value1 Set the temperature control knobs to their max.

position and run the boiler in d.h.w. and c.h.2 Allow the boiler to reach its maximum operating

temperature (monitor the temperature gauge onthe instrument panel). The boiler should maintaina temperature below that of the safety thermostatand no overheat intervention should occur.

n Electrical function1 Remove all the case panels and the lid of the

sealed chamber.

2 Disconnect the safety thermostat and check itselectrical function. Normally (no intervention) thecontact must be closed (electrical resistance zeroW).


1 Remove all the case panels and the lid of thesealed chamber.

1b For model M90.28S only, remove the screw B andthe plate C (Fig. 71).

B

C

Fig. 71

2 Disconnect the wiring D (Fig. 72).3 Remove the spring E which holds the overheat

thermostat on the pipe of the primary heat ex-changer and remove it.

D

E

Fig. 72

4 Reassemble the overheat thermostat carrying outthe operations in reverse order.

5 Apply an adequate quantity of heat conductingcompound between the pipe and the thermostat.

34

19 Short spare parts listKey G.C. part no. Description Q.ty Manufac-

turer part no.Manufacturer’s reference

1 173---148 Burner (mod. M90.24S) 1 KI1004 102 Polidoro173---149 Burner (mod. M90.28S) 1 KI1004 147

2 169---069 Injectors for natural gas (mod. M90.24S) 12 KI1064 505 PolidoroInjectors for natural gas (mod. M90.28S) 14

169---070 Injectors for LPG (mod. M90.24S) 12 KI1064 506Injectors for LPG (mod. M90.28S) 14

3 Expansion vessel 1 BI1172 103 CIMM 6 litres4 Main heat exchanger (mod. M90.24S) 1 BI1172 100

Main heat exchanger (mod. M90.28S) 1 BI1172 1065 Fan (mod. M90.24S) 1 BI1336 104

Fan (mod. M90.28S) 1 BI1336 1056 Gas valve 1 BI1093 104 SIT 845 Sigma7 E05---422 Air pressure switch (mod. M90.24S) 1 BI1036 102 Yamatake---Honeywell C6065

169---127 Air pressure switch (mod. M90.28S) 1 KI1267 1038 Safety valve 1 BI1131 100 Orkly9 Combustion chamber side panels 2 BI1326 10010 Combustion chamber rear panel (mod. M90.24S) 1 BI1326 107

Combustion chamber rear panel (mod. M90.28S) 1 BI1326 10811 Combustion chamber front panel (mod. M90.24S) 1 BI1326 101

Combustion chamber front panel (mod. M90.28S) 1 BI1326 10212 Electronic regulation p.c.b. 1 BI1475 11613 Full sequence ignition device 1 BI1305 101 Bertelli & Partners FM3014 E01---204 D.h.w. heat exchanger (mod. M90.24S) 1 BI1001 101

E01---205 D.h.w. heat exchanger (mod. M90.28S) 1 BI1001 10215 Pump 1 BI1172 104 Wilo --- NFHUL 15/516 E00---684 Primary circuit flow switch 1 BI1011 50517 D.h.w. flow switch 1 BI1091 10418 E00---688 Main. flow switch membrane 1 BI1011 10319 Three way diverter valve (electric actuator) 1 BI1011 102 Elbi20 Overheat thermostat 1 BI1172 105 ELTH --- type 26121 169---083 Fuse 1,6 A T 1 BI1005 10522 164---026 Temperature probe (main or d.h.w. circuit) 1 BI1001 11723 Ignition electrode (left) 1 BI1123 10124 Ignition electrode (right) 1 BI1123 10325 Detection electrode 1 BI1123 10226 Temperature---pressure gauge 1 BI1475 108 IMIT

Short spare parts list

35

1 2

64

5

7

3

8

15 18

12 13

20 21 22 23 25 26

14 16

24

17 19

9

10

11 9

*1796208420*17962.0842.0 --- 0701 10A3

biasi service manual

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