Wall hung, fan flue, room sealed gas boiler

SERVICE MANUAL Parva

Models: G.C. Appl. No. 47--970--13 47--970--14

M90.24S M90.28S

Leave this manual adjacent to the gas meter
Biasi U.K. Ltd Unit 32/33, Planetary Road Industrial Estate, Neachells Lane Willenhall, Wolverhampton WV 13 3XB Tel: 400

Table of contents

1 1.1 1.2.1 2.2 2.3 2.4 2.5 2.3.1 3.2 3.5 5.1 5.2 5.6.1 6.7.1 7.2 7.8.1 8.2 8.3 8.9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 9.10 9.11 Overall information. Overall View. Hydraulic diagram. General access and emptying hydraulic circuits. Nomenclature. Body panels. Control panel. Access to the sealed chamber. Emptying the primary circuit. Emptying the d.h.w. circuit. Diagrams. Wiring diagram. Functional flow diagrams. Circuit voltages. Fault finding. Primary heat exchanger. Characteristics. Removal. Cleaning. 10.1 10.2 10.3 10.11.1 11.2 11.3 11.4 11.12.1 12.2 12.13.1 13.2 13.3 13.4 13.5 13.14.1 14.2 14.15.1 15.16.1 16.2 16.3 16.17.1 17.2 17.18.1 18.2 18.Full sequence ignition device. Function. Checks. Removal. Ignition and control sequence. Modulating gas valve. Function. Nomenclature of the parts. Adjustment. Checks. Removal. Primary circuit flow switch. Function. Checks. Removal. D.h.w. flow switch, filter and flow limiter Function. Nomenclature and location of parts. Checks. Removal of the flow switch sensor. Removal of the flow switch group and d.h.w. circuit filter. Flow limiter. Temperature probe. Function. Checks. Removal. 28 28
D.h.w. heat exchanger. 10 Function. 10 Removal. 10 Pump. Function. Checks. Removal. Three way diverter valve. Function. Checks. Removal of the electric actuator. Removal of the diverter group and its internal parts. Electronic control p.c.b. Function. Selection and adjustment devices. Checking the temperature. Operation/Service lamps. Dip---switch selectors. Ignition gas pressure adjustment. Max c.h. power adjustment. Checks. Removal of the electronic control p.c.b. Thermal control in the mode. Thermal control in the 17 19
By -- pass valve. 29 Function. 29 Removal. 29 Fan and Air pressure switch. Function. Checks. Removal of the Fan. Removal of the Air pressure switch. Ignition and detection electrodes. Function. Checks. Removal. Safety thermostat. Function. Checks. Removal. 33

mode. 19

Short spare parts list. 34

Overall information

Overall View

Fan Expansion vessel

Air pressure switch Main heat exchanger

Safety thermostat

Burner

Combustion chamber

Ignition electrodes Detection electrode Diverter valve Main circuit flow switch Gas valve Control panel
Automatic air release valve D.h.w. temp. probe Pump D.h.w flow switch

D.h.w. heat exchanger

Hydraulic diagram
Central heating (c.h.) operation
Domestic hot water (d.h.w.) operation

C.h. water return

C.h. water flow

D.h.w. inlet

D.h.w. outlet
General access and emptying hydraulic circuits

Nomenclature

Fig. 2 3
To remove the side panels loosen the screws B and C (Fig. 3), bring the base of the panels away from the boiler and lift them, freeing them from the top hooks.

Fig. 1

Right side panel Front panel Control panel lid Control panel cover Service panel Left side panel
Fig. 3 --- bottom view of the boiler C D C

Control panel

Warning: isolate the boiler from the mains electricity supply before removing any covering or component.

Body panels

For the most part of the check and maintenance operations it is necessary to remove one or more panels of the case. The side panels can be removed only after the removal of the front panel. To remove the front panel remove screws A (Fig. 2), lift the panel and remove it.
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 B and C (Fig. 3). 3 Remove the screws D 4 Move the lower part of the side panels as indicated in Fig. 4 and pull the control panel. When completely pulled out, the panel can rotate 45 downwards to facilitate the service operations on the internal parts.
General access and emptying hydraulic circuits 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 G as indicated in Fig. 6 and remove the lid.

Fig. 4

Emptying the primary circuit
Close the c.h. circuit flow and return cocks H. (Fig. 7).
Remove the screws E and remove the service panel (Fig. 5); To gain access to the electronic regulation PCB and the full sequence ignition device remove the screws F and remove the control panel lid (Fig. 5);

230~ 0 230~
Full sequence Ignition device

Modulating Gas valve

Safety thermostat Fan

3 way diverter valve

Components to check --(3) --(4) --(5) 6 7.2 8.2 9.8 10.2 11.4 12.2 13.5 14.16.2 17.2 18.2 --(8) --(9) -----

Fault finding

Section of the manual ! (note ref. in brackets)

Defect #

Appliance operation lamp green (1)
Lock--- out signal lamp red

Flue pipes

D.h.w. circuit
Fuse (regulation p.c.b.) Regulation p.c.b.

Full sequence device

Gas valve (modulating operator) Main circuit flow switch

Ignition electrode

Detection electrode
Safety valve Injectors J J J J J J J J J

Power supply line

Gas supply line

C.h. circuit

Diverter valve
Function selectors (reg. p.c.b)
Gas valve (on--- off operators)

D.h.w. filter

Main circuit temp. probe

D.h.w. temp. probe

By--- pass valve

Fan and venturi device

The boiler does not start either in c/h or d.h.w. mode. Fan still. J J J J (7)
By pressing the reset push--- button the boiler turns on and operates correctly.
By pressing the reset push--- button the boiler starts the ignition cycle. The burner doesnlight on, the ignit tion sparks continue and the boiler locks again. J J

ON --- fast pul ulses

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
The burner doesnlight either in c.h. t or d.h.w. mode. Fan turn. J
The burner doesnlight either in c.h. t or d.h.w. mode. Fan doesnturn. t
The boiler doesncontrol the d.h.w. t temperature. Turning the d.h.w. temp. adjustment knob hasneffect on the modulation of t the flame. The boiler operates correctly on c.h.

ON --- fas pulses st

The boiler lights for a short while on c.h. Normal operation on d.h.w. function.

Expansion vessel

Pressure gauge
Safety valve Injectors J J J J
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 J J
On c/h mode the temperature of the main circuit reaches 75 and the c/h C system does not heat. The boiler operates correctly on d.h.w. mode. J J J J J J

Incorrect modulation

J3 connector J2 connector Lock ---out signal lamp Boiler reset button Function control / C.h. temperature adjustment D.h.w. temperature adjustment Service lamps (service mode) Appliance operation lamp (normal use mode) Dip---switch selectors Setting jumpers Ignition gas pressure adjustment (ACC.) Maximum c.h. gas pressure adjustment (RISC.) J1 connector Fuse 1,6 A T

Checking the temperature

Fig. 28
The Electronic control 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 electric signal by means of temperature probes.
Electronic control p.c.b. The user, setting the desired temperature with the control panel knobs operates the variable elements (5 and 6 in Fig. 29) of the electronic control p.c.b. If the power requested is lower than 40% of the maximum power output then control is achieved by switching ON the burner at minimum power, then switching OFF (ON/OFF function). If the power requested is higher, then the burner is switched ON at maximum power and will control by modulating to 40% of the maximum power output. During the c.h. operation (Fig. 30), the signal coming from the c.h. temperature probe is compared to the signal given by the control panel through the adjustment made by the user (knob ). The result of such a comparison operates the modulation of the gas valve, consequently changing the useful output of the boiler.

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 the useful output is C, automatically reduced so that the primary circuit cannot reach excessive temperatures. function and in funcThe control sequences in tion are illustrated in detail in sections 9.10 and 9.11.

Electronic control p.c.b. f Selector 2 (Technical information section, Gas pressures at the burner table). By rotating the device clockwise the pressure increases. Check the regular ignition of the burner by turning the boiler on and off repeatedly. After the adjustment operations bring the selector 3 back to the normal position (ON).
This selects the boiler functions on the basis of the type of gas used. It allows the selection of the maximum supply current given to the modulator device. To set selector 2 correctly follow the table in Fig. 33.
Gas supply Position of selector Approx. Max current through the modulator device 120 mA 165 mA
Max c.h. power adjustment
Natural gas L.P.G. Fig. 33

On Off

Selector 3
By using device 12 (Fig. 29) marked RISC.on the Electronic control p.c.b., you can limit the maximum useful output delivered during the c.h. operating mode. This adjustment does not influence the maximum useful output delivered during the d.h.w. operating mode. By rotating the device clockwise the pressure increases.
This forces the functioning of the boiler in order to allow the optimal gas pressure at the burner to be adjusted during the ignition phase. The adjustment (see section 9.6) is done by means of the potentiometer marked 11 ACC (Fig. 29 on page 14). After the adjustment operations bring the selector back to the normal position (ON). ON (1) OFF (0) gas pressure calibration

Fig. 34

Check that the fuse is complete
If the Electronic control p.c.b. does not supply any device (pump, fan, etc.) check that the fuse 14 (Fig. 29) is complete. If the fuse has blown replace it with one that has the same characteristics after having identified the reason for failure. n Check the setting jumpers position

Normal

Two setting jumpers must be fitted on the Electronic control p.c.b. as shown in Fig. 36. The numbers refer to the marking printed on the circuit board.

Selector 4

This allows you to select the minimum time that must pass between two ignitions of the burner in c.h. function. ON (1)

Fig. 36

30 sec.

Fig. 35

OFF (0)

3 min.

Removal of the electronic control p.c.b
Ignition gas pressure adjustment
By using the device 11(Fig. 29) marked ACC.on the Electronic control p.c.b., it is possible to adjust the gas pressure at the injectors in the ignition phase. This pressure is maintained at the injectors until ignition occurs (ionization signal from the full sequence ignition device). To carry out the adjustment move the function selector 3 to the OFF position (Fig. 34) and use the adjustment device 11(ACC). Adjust the gas pressure at the injectors to the value indicated in the tables of the User/Installation manual
Gain access to the parts located inside the control panel as explained in the section 2.3 of this manual. Remove all the wiring connected to the Electronic control p.c.b. To disconnect the connectors J1, J2 and J3 (13, 2 and 1 in Fig. 29) delicately flex the hook present on one side of each socket. Remove the spindles of the c.h. and d.h.w. temperature adjustment knobs by delicately pulling them with pliers in the direction shown by the arrow in Fig. 37. 17
Electronic control p.c.b. 9 While tightening the screws that fix the Electronic control p.c.b. on the control panel, keep the p.c.b. towards the control panel fascia making sure of the contact between the boiler reset button B and the tab C (Fig. 38).

Fig. 37

Unscrew the four screws that hold the Electronic control p.c.b. on to the control panel. Remove it by lifting its rear edge and freeing it from any of the wiring. Re---assemble the Electronic control p.c.b. following the removal procedures in the reverse order.

A Fig. 38

Attention After installing the Electronic control p.c.b. : 10 ) temMake sure the c.h. ( ) and d.h.w. ( perature adjustment knobs can move freely for the complete range. If not, remove the spindle again as described at step 3, turn the knob half a turn and re---insert the spindle. Operate the boiler and close the gas inlet cock so that the boiler goes into the safety lock ---out state. Verify the correct operation of the boiler reset button by pressing and releasing it.

Important When re---assembling the Electronic control p.c.b.: 7 Fit the p.c.b. into the control panel by first inserting the front lower edge under the control knob shafts. Lower the rear edge and ensure that no wiring is trapped beneath. Insert the spindles in the control panel knobs untill the notch A (Fig. 38) reaches the potentiometer edge. It is not necessary to force them in the knob.
9.10 Thermal control in the mode

Switch in the

See functioning with the function control in the mode (sec. 9.11)

function mode

Taking water from the domestic hot water circuit?
Is primary circuit temperature higher than that selected?
NO Circulator off Operates motorised valve Ignition device off Fig. 39
Request for heat from room thermostat?
YES Starts the circulator Operates motorised valve Supplies the ignition device
9.11 Thermal control in the
Switch in the function mode
Circulator off Ignition device off

Circulator on

Is domestic hot water outlet temperature lower than that required?
Supplies the ignition device Fig. 40

Ignition device off

With the burner firing, interrupt the gas supply. The Full sequence ignition device must carry out a complete ignition cycle and then stop. By turning the boiler on and off by means of the function switch the device must not unlock and the burner must not turn on. n Control of flue gas expulsion With the boiler operating and the burner on, open the negative pressure test point of the Venturi device. At the moment of opening the burner must turn off.
The Full sequence ignition device used on the boiler carries out the following fundamental functions: f f f does a sequence of operations (ignition cycle) which lead to the ignition of the gas at the burner 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 Full sequence ignition device is supplied by the electronic control p.c.b. when the ignition of the burner is requested. The Full sequence ignition device has a safety function and any incorrect interventions or tampering can result in conditions of dangerous functioning of the boiler. The Full sequence ignition device can lock the functioning of the boiler (lock state) and stop its functioning up to the resetting intervention. The lock is signalled by the lighting of the lock ---out signal lamp and the device can be reset only by using the boiler reset button placed on the control panel fascia. Some components which are connected to the device can activate the lock state. The causes of a lock state could be: f f f f f f f The intervention of the safety thermostat (overheat of the primary circuit). A fault on gas feeding Faulty ignition (faulty ignition electrodes, their wiring or connection). Faulty flame detection (faulty detection electrode, its wiring or connection). Gas injectors blocked Faulty modulation gas valve (faulty on---off operators or not electrically supplied). Faulty Full sequence ignition device.

Fig. 43

By means of an electric command given to the on---off operators the passage of the gas through the Modulating gas valve can be opened or closed. By means of an electric command given to the modulation operator the pressure can be varied and therefore the gas flow rate to the burner (modulation). The modulation operator has mechanical components which allow the adjustment of the minimum and maximum pressure exiting the valve. 7
Nomenclature of the parts (Fig. 44)
Modulation operator electric connectors s Minimum gas pressure adjustment On---off operators Maximum gas pressure adjustment On---off operators electric connector Gas valve inlet pressure test point Modulation operator Gas valve outlet pressure test point
Important: after the gas pressure checks and any adjustment operations, all of the test points must be sealed.
Check the modulation operator coil Remove the front panel of the case. Disconnect the connectors B (Fig. 46) from the modulating operator and measure the electrical resistance of the coil. Its electrical resistance value must be approx. 80 W*. Check the on---off operators coils Remove the front panel of the case. Disconnect the electrical connector C (Fig. 46). Measure the electrical resistance between the connector pins of the on---off operators as illustrated in Fig. 45.
Remove the front panel of the case as explained in the section 2.3 of this manual. Disconnect the connectors B and C (Fig. 46). Turn off the gas supply and disconnect the gas isolation cock connector from the inlet port of the gas valve. Unscrew the connectors D and remove the pipe E Unscrew the screws F and remove the valve. Reassemble the valve carrying out the removal operations in reverse order.
After any service operation on the components of the gas circuit check all the connections for gas leaks.
Upper on---off operator approx. W* Lower on---off operator approx. 920 W* * at ambient temperature.

Fig. 45

E D B C

Fig. 46

Primary circuit flow switch
The Primary circuit flow switch (A in Fig. 47) function is to detect water flowrate through the primary hydraulic circuit of the boiler.
Mechanical function Remove the front panel of the case. Start and stop the boiler either in d.h.w. or c.h. mode. Looking through the switch box verify the position of the shaft B referring to Fig. 49.

Boiler OFF

A Fig. 49

Boiler ON

Electrical check
It is possible to verify the general operation of the switch by measuring the electric resistance between the contacts 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 the contact is now closed.

C Fig. 47 N.O.

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

do not use Fig. 50

Removal of the switch Remove the front and right hand side panels of the case. Remove the fork C (Fig. 48). Open the box and disconnect the switch. Re---assemble the parts proceeding in reverse order of removal. Refer to Fig. 50 for the correct wiring connectors on the switch

Removal of the membrane

Remove the front and right hand side panels of the case, turn off the flow and return isolation valves and empty the primary circuit. Remove the fork C that holds the micro---switch housing D (Fig. 48). Unscrew the four screws E (see Fig. 51) open the hydraulic operator and remove the membrane F.

Fig. 48

F G E H
Reassemble the parts in reverse order of removal.
When assembling the membrane, ensure that its concave side faces towards the actuator plate G and the reference indicated aligns with the seat H (see Fig. 51).

Fig. 51

D.h.w. flow switch, filter and flow limiter
Nomenclature and location of parts (Fig. 54)
Flow switch sensor Plug Magnetic ring Float Spring Filter Body Spring seat Flow limiter (M90.28S optional accessory) Threaded ring
The d.h.w. flow switch A in Fig. 52 is a device that generates an electrical signal when hot water is drawn.

7 A Fig. 6

Fig. 52
When the flow rate through the d.h.w. circuit reaches about 2,5 litres/min the float 4 (Fig. 54) is drawn to, wards the right. The resulting magnetic field of ring 3 increases and reaches the flow switch sensor 1. The sensor generates an electrical signal that switches the boiler d.h.w operation ON. The state of the sensor is also indicated by means of the lamp B placed on the sensor body.

Flow switch sensor operation Remove the front panel of the case. Switch on the boiler and open a d.h.w. tap. The lamp B (Fig. 53) placed on the sensor body is switched on when the flow rate reaches about 2,5 litres/min.
Removal of the flow switch sensor
Remove the front panel of the case. Disconnect the connector C (Fig. 53) and remove the sensor by pulling it towards the front of the boiler (the sensor is held in place by means of a spring).
Removal of the flow switch group and d.h.w. circuit filter

Fig. 53

Remove the front panel of the case and empty the d.h.w. circuit.
D.h.w. flow switch, filter and flow limiter Remove the flow switch sensor (see section 13.4). Remove the gas valve (see section 11.5). Unscrew the plug 2 (Fig. 54) and extract the flow switch group. To remove the filter from the flow switch group separate the body 7 from the plug 2 (Fig. 54) by unscrewing it. Reassemble the parts following the removing sequence in reverse order. If on the M90.28S model the flow rate of the d.h.w. circuit is too high, it is possible to limit it by installing a flow limiter. The following sizes are available: Nominal flow rate (litres/min) Colour Yellow Brown

Flow limiter

The M90.24S model is factory fitted with a 10 litre/min. flow limiter.
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 remove it from the body 7. 3 Install the flow limiter 9 putting its smaller diameter side towards the threaded ring. 4 Reassemble the group following the above sequence in reverse order.

Temperature probe

Temperature---resistance relationship Warning: isolate the boiler from the mains electricity supply before removing any covering or component.
The Temperature probe has the function of converting the temperature of the water in the hydraulic circuit where it is installed into an electrical signal (resistance). The relation between temperature and electrical resistance is stated in Fig. 55. W 12500
Disconnect the cable from the Temperature probe. Measure the temperature of the brass group where the Temperature probe is located and check the electrical resistance according to the graph in Fig. 55.
Warning: isolate the boiler from the mains electricity supply before removing any covering or component. Refer to Fig. 57 for the c.h. Temperature probe and to Fig. 58 for the d.h.w. Temperature probe.
To remove the Temperature probes remove the front and right hand side panels of the case. Empty the primary circuit of the boiler. Remove the electric connector of the Temperature probe and unscrew it. Reassemble the Temperature probe carrying out the removal operations in reverse order.

Fig. 55

On the boiler there are two Temperature probes. One on the output of the primary heat exchanger (c.h. Temperature probe) A in Fig. 56 and Fig. 57; one on its input, before the pump (d.h.w. Temperature probe) B in Fig. 56 and Fig. 58.

Fig. 63

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

Fig. 66

G Fig. 64
Removal of the Air pressure switch
Remove the three screws securing the Fan to the flue hood. Assemble the fan carrying out the removal operations in reverse sequence.
Remove all the case panels and the sealed chamber lid. Disconnect the wires from the Air pressure switch. Remove the pipes from the Air pressure switch. Unscrew the screws which hold the Air pressure switch to the frame. Assemble the Air pressure switch carrying out the removal operations in reverse sequence.
Warning: to correctly connect the venturi device to the Air pressure switch, refer to Fig. 65 for the model M90.24S and to Fig. 66 for the model M90.28S.

Fig. 65

Warning: to correctly connect the Air pressure switch, refer to Fig. 65 for the model M90.24S, to Fig. 66 for the model M90.28S and Fig. 62 for the correct wiring.
Ignition and detection electrodes
Check the integrity of the detection electrode and ensure that its metallic edge is correctly placed over the ramp of the burner. Check the connection wires. Warning: isolate the boiler from the mains electricity supply before removing any covering or component.
Three electrodes are fitted on the burner. Two of them are the ignition electrodes and are fitted near the front part of the burner. The ignition sparks take place between their metallic edges over the central ramp of the burner during the ignition sequence. The third electrode is the detection electrode and it detects the presence of the flame. Detection Ignition Male
Remove all the case panels, the sealed chamber lid and the combustion chamber lid. Check for the integrity of the insulation of wires which connect the electrodes to the ignition device.

Female 3

Remove all the case panels, the sealed chamber lid and the combustion chamber lid. Disconnect the electrode wires from the full sequence ignition device. Remove the burner by unscrewing the four screws placed at the right and left sides of the burner. For model M90.28S only, remove also the plate F (see Fig. 63 on page 30). Unscrew the screws A (Fig. 69) which hold the electrodes to the burner.

Fig. 67

Check the position of the electrode edges Warning: isolate the boiler from the mains electricity supply before removing any covering or component.
Remove all the case panels, the sealed chamber lid and the combustion chamber lid. Check for the correct distance between the metallic edges of the ignition electrodes (see Fig. 68). 4 mm

Ignition

Fig. 69
Extract the electrodes from the burner. Assemble the electrodes carrying out the removal operation in reverse order. Refer to Fig. 67 in order to recognize the electrodes and to correctly connect the wiring.

Fig. 68

Note: the metallic edge of the detection electrode is longer than the one of the ignition electrodes.
The safety thermostat A in Fig. 70 is a device that senses the temperature of the primary circuit water which flows in the outlet pipe of the primary heat exchanger. If the temperature control system of the boiler fails and the temperature of the primary circuit reaches a dangerous temperature, the safety thermostat opens the electric circuit that supplies the on---off operators of the gas valve. Consequently, the full sequence ignition device attempts to light the burner and, at the end, locks the boiler and lights the lock ---out signal lamp.
Disconnect the safety thermostat and check its electrical function. Normally (no intervention) the contact must be closed (electrical resistance zero W).
Remove all the case panels and the lid of the sealed chamber. For model M90.28S only, remove the screw B and the plate C (Fig. 71).

B Fig. 71

Disconnect the wiring D (Fig. 72). Remove the spring E which holds the overheat thermostat on the pipe of the primary heat exchanger and remove it.

Fig. 70

Overheat temperature value Set the temperature control knobs to their max. position and run the boiler in d.h.w. and c.h. Allow the boiler to reach its maximum operating temperature (monitor the temperature gauge on the instrument panel). The boiler should maintain a temperature below that of the safety thermostat and no overheat intervention should occur. Electrical function Remove all the case panels and the lid of the sealed chamber.

Fig. 72

Reassemble the overheat thermostat carrying out the operations in reverse order. Apply an adequate quantity of heat conducting compound between the pipe and the thermostat.

Short spare parts list

Description Burner (mod. M90.24S) Burner (mod. M90.28S) Injectors for natural gas (mod. M90.24S) Injectors for natural gas (mod. M90.28S) 169---070 Injectors for LPG (mod. M90.24S) Injectors for LPG (mod. M90.28S) Expansion vessel Main heat exchanger (mod. M90.24S) Main heat exchanger (mod. M90.28S) Fan (mod. M90.24S) Fan (mod. M90.28S) Gas valve E05---422 169---127 Air pressure switch (mod. M90.24S) Air pressure switch (mod. M90.28S) Safety valve Combustion chamber side panels Combustion chamber rear panel (mod. M90.24S) Combustion chamber rear panel (mod. M90.28S) Combustion chamber front panel (mod. M90.24S) Combustion chamber front panel (mod. M90.28S) Electronic regulation p.c.b. Full sequence ignition device E01---204 E01---205 D.h.w. heat exchanger (mod. M90.24S) D.h.w. heat exchanger (mod. M90.28S) Pump E00---684 E00---688 Primary circuit flow switch D.h.w. flow switch Main. flow switch membrane Three way diverter valve (electric actuator) Overheat thermostat 169---083 164---026 Fuse 1,6 A T Temperature probe (main or d.h.w. circuit) Ignition electrode (left) Ignition electrode (right) Detection electrode Temperature ---pressure gauge Q.ty ManufacManufacturer reference s turer part no. BIBIBIBIBIBIBIKIBIBIBIBIBIBIBIBIBIBIBIBIBIBIBIBIBIBIBIBIBIBIIMIT Elbi ELTH --- type 261 Wilo --- NFHUL 15/5 Bertelli & Partners FM30 Orkly SIT 845 Sigma Yamatake ---Honeywell C6065 CIMM 6 litres KIKIKIKIPolidoro Polidoro 173---148 173---149 169---069

Key G.C. part no.

*1796208420*
17962.0842.0 --- 0701 10A3