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Savio GAIA 424 S Service Manual

Wall hung, fan flue, room sealed gas boiler
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Service manual
Models covered by these instructions
424 S
428 S
424 RS
Wall hung, fan flue, room sealed gas boiler
GAIA
Leave this manual adjacent to the gas meter
BIASI S.p.A.
37135 Verona (Italy)
Via Leopoldo Biasi, 1
Stabilimento:
33170 Pordenone (Italy)
Via Pravolton, 1/B
Table of contents
1
Overall information
1.1
Overall View
1.2
Hydraulic diagram
2
General access and emptying hydr. circuits
2.1
Nomenclature
2.2
Body panels
2.3
Access to the electric parts of the control panel
2.4
Access to the sealed chamber
2.5
Emptying the main circuit
2.6
Emptying the d.h.w. circuit
3
Diagrams
3.1
Wiring diagram
3.2
Functional flow diagrams
3.3
Control circuit voltages
4
Fault finding
5
Main heat exchanger
5.1
Characteristics
5.2
Removal
5.3
Cleaning
6
D.h.w. heat exchanger
6.1
Function
6.2
Removal
7
Pump
7.1
Function
7.2
Checks
7.3
Removal
8
Diverter valve and d.h.w. pressure switch
8.1
Function
8.2
Checks
8.3
Removal
9
Electronic control circuit
9.1
Function
9.2
Selection and adjustment devices
9.3
Checking the temperature
9.4
Function selectors
9.5
Ignition gas pressure regulator
9.6
Max. c/h power regulator
9.7
Checks
9.8
Removal of the control circuit
9.9
Thermal control in the mode
9.10
Thermal control in the mode
10
Display circuit
10.1
Function
10.2
Display circuit operation
10.3
Removal
11
Full sequence ignition device

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Summary of Contents for Savio GAIA 424 S

  • Page 1 Service manual Models covered by these instructions 424 S 428 S 424 RS Wall hung, fan flue, room sealed gas boiler GAIA Leave this manual adjacent to the gas meter BIASI S.p.A. 37135 Verona (Italy) Via Leopoldo Biasi, 1 Stabilimento: 33170 Pordenone (Italy) Via Pravolton, 1/B Table of contents...

  • Page 2: Overall Information

    11.1 Function 11.2 Checks 11.3 Removal 11.4 Ignition sequence Gas valve 12.1 Function 12.2 Nomenclature of the parts 12.3 Adjustment 12.4 Checks 12.5 Removal Main circuit flow switch 13.1 Function 13.2 Checks 13.3 Removal D.h.w. filter and flow limiter 14.1 General notes 14.2 Removal of the filter...

  • Page 3: General Access And Emptying Hydraulic Circuits

    1.2 Hydraulic diagram fig. 2 2 General access and emptying hydraulic circuits 2.1 Nomenclature...

  • Page 4: Body Panels

    fig. 3 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 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.
  • Page 5 Lift the front panel freeing it from the hooks placed on its left and right side. To remove the side panels loosen the screws B (fig. 5), bring the base of the panels far from the boiler and lift them, freeing them from the side hooks of the frame.

  • Page 6: Access To The Sealed Chamber

    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 remove the four screws D (fig. 7) and remove the cover pulling it towards the front. fig.

  • Page 7: Emptying The D.h.w. Circuit

    To facilitate the downflow of water, remove the front panel, also remove the sealed chamber cover and loosen the nut H (fig. 10) of the automatic air bleed valve. Tight it again once the emptying has been completed. 2.6 Emptying the d.h.w. circuit 1.

  • Page 8: Functional Flow Diagrams

    3.2 Functional flow diagrams General layout function switch position off...
  • Page 9 Function switch position Heat request on c/h Function switch position Heat request on d.h.w. Function switch position Heat request on d.h.w.

  • Page 10: Control Circuit Voltages

    3.3 Control circuit voltages a: never zero (short circuit) never 12V= (open circuit) Electrical voltages in Volts during normal operation with burner on at maximum power 4 Fault finding...

  • Page 12: Main Heat Exchanger

    5 Main heat exchanger 5.1 Characteristics The main heat exchanger (A in fig. 12) has the function of transferring heat of the gas produced by combustion to the water circulating in it. fig. 12 The hydraulic circuit consists of five elliptic pipes connected together in series (fig.
  • Page 13 5.2 Removal WARNING: isolate the boiler from the mains electricity supply before removing any covering or component. 1 Empty the main circuit of the boiler 2 Remove the front panel of the case 3 Remove the sealed chamber cover. For models 424 S, 424 RS… 4a Remove the cover of the combustion chamber;...
  • Page 14 6 Unscrew the automatic air valve connection nut D and remove the valve (fig. 14a); 7 Separate the heat exchanger from the hydraulic circuit, loosening the inlet and outlet pipe fittings; For models 424 S, 424 RS… 8a move the right pipe and free the right connection; lower the right side of the exchanger and extract it from the front; For model 428 S…...
  • Page 15 6.2 Removal WARNING: isolate the boiler from the mains electricity supply before removing any covering or component. 1. Empty the primary circuit and the d.h.w circuit of the boiler 2. Remove the front panel of the case and lower the instrument panel 3.
  • Page 16 7 Pump 7.1 Function The pump (A in fig. 19) has the function of making the water in the main circuit circulate through the main heat exchanger and therefore through the c/h system (during the c/h function) or through the secondary heat exchanger (during the d.h.w. function). fig.

  • Page 17: Diverter Valve And D.h.w. Pressure Switch

    Check that the impeller is integral with the rotor. Remove the pump head loosing the screws which hold it to the pump body and check that the impeller is firmly jointed with the rotor. 7.3 Removal WARNING: isolate the boiler from the mains electricity supply before removing any covering or component. If the clearance to the right side of the boiler is restricted, the removal of the pump can be easily achieved by first removing the head by unscrewing the four Allen keys screws (B in fig.
  • Page 18 1. Switch off the boiler and open the control panel. 2. Connect a meter, set for direct voltage measurement, to the points indicated in fig. 3. Switch the boiler on position and verify the voltages during c/h and d.h.w. by matching the readings with the values indicated in the section 3.3.
  • Page 19 fig. 27 Assembling the part, ensure to place the concave side of the membrane towards the actuator plate I ( fig. 27 When fixing the actuator to the valve, fit the reference shaft J in the seat of the valve ( fig.
  • Page 20 Removal of the switch 1. Switch off the boiler; remove the front panel of the case, the lower protection plate and lower the control panel. 2. Remove the fork K that holds the d.h.w. pressure switch L placed on the right side of the valve and remove the switch (fig.
  • Page 21 fig. 32 fig. 33 The diverter mechanism is composed by two parts. To reach them remove the hydraulic actuator as explained at the step 3 of the part Removal of the membrane of this chapter. With a suitable spanner unscrew both plugs indicated in fig.

  • Page 22: Electronic Control Circuit

    Reassemble the valve proceeding in the reverse order. 9 Electronic control circuit 9.1 Function The fundamental function of the control circuit is that of controlling the boiler in relation to the external needs (heating the room, heating the water for d.h.w.

  • Page 23: Checking The Temperature

    Several of these devices are directly accessible by the user (function switch, temperature adjustment potentiometers etc.) others are accessible by removing the cover. 9.3 Checking the temperature The control circuit makes it possible to separately adjust the c/h water flow and d.h.w. outlet temperature. The temperatue of the water is converted into an electric signal by means of temperature probes.

  • Page 24: Function Selectors

    Normally, the result of the comparison between these two signals directly operates the adjustment elements of the gas valve, adjusting the useful output generated in order to stabilize the temperature of the exiting water. If during the functioning in d.h.w. mode, the temperature of the primary circuit goes over 75°, the useful output is automatically reduced so that the primary circuit cannot reach excessive temperatures.

  • Page 25: Ignition Gas Pressure Regulator

    The adjustment (see section 9.5) is done by means of the potentiometer “8” marked “ACC. ”(fig. 36). After the adjustment operations bring the selector back to the normal position (ON). fig. 41 Selector 4 It makes it possible to select the minimum time that must pass between two ignitions of the burner in c/h function. fig.

  • Page 26: Removal Of The Control Circuit

    The F2 fuse can be reached by removing the panel cover. If the fuse is blown replace it with one that has the same characteristics after having identified the cause of the interruption. 9.8 Removal of the control circuit WARNING: isolate the boiler from the mains electricity supply before removing any covering or component.
  • Page 27 3. extract the spinldes and insert them with the flat side pointing in the direction shown in fig. 4. position the spindles as in fig. 49 and mount the panel cover. fig. 47 fig. 48 fig. 49 After having installed the control panel make sure the central heating ( ) and domestic hot water temperature ( ) adjustment knobs can move freely (half a turn).

  • Page 28: Display Circuit

    9.10 Thermal control in the “ ” mode fig. 51 10 Display circuit 10.1 Function The boiler is equipped with a pcb that displays some information about the operation of the appliance. The electric signals that operate the display circuit are given directly by the electronic control circuit or by the water pressure switches. fig.

  • Page 29: Display Circuit Operation

    10.2 Display circuit operation The following drawing (fig. 53) and list illustrate the position of each light and its function. fig. 53 The colours are referred to the transparent windows of the control panel cover. 1 Boiler on - green It indicates the operation of the boiler.

  • Page 30: Full Sequence Ignition Device

    The lights are turned on referring to the signal that comes from the central heating temperature probe. Consequently, the reading of the temperature can be altered by a faulty temperature probe. 10.3 Removal WARNING: isolate the boiler from the mains electricity supply before removing any covering or component. 1.

  • Page 31: Ignition Sequence

    fig. 56 11.4 Ignition sequence fig. 57...

  • Page 32: Gas Valve

    12 Gas valve 12.1 Function...

  • Page 33: Nomenclature Of The Parts

    The gas valve controls the gas inflow to the boiler burner. By means of an electric command given to the on-off operators the passage of the gas through the valve can be opened or closed. By means of an electric command given to the modulating operator the pressure can be varied and therefore the gas flow rate to the burner (modulation).

  • Page 34: Main Circuit Flow Switch

    9. turn the boiler off and connect the wire to the modulating operator; 10. start the boiler; 11. rotate the maximum pressure adjuster “6” until you obtain the espected pressure (by rotating clockwise the pressure increases); 12. turn the boiler off and disconnect the gauge; At the end of the adjustment ensure to seal the gas test point.
  • Page 35 13.1 Function The main circuit flow switch (A in fig. 62) is a device that controls the speed of water that crosses the main heat exchanger. fig. 62 This device controls the regular functioning of the pump, the presence of water in the primary circuit of the boiler and the absence of obstructions of the main heat exchanger during the c/h function as well as during the d.h.w.
  • Page 36 Mechanical function 1. Remove the front panel of the case and lower the control panel as described in the section 2.2 of this manual. 2. Remove the fork C that holds the main circuit flow switch B (fig. 64). 3. Start and stop the boiler in c/h operation (time switch and external controls must call for heat) and verify the position of the shaft D referring to fig.

  • Page 37: General Notes

    Assembling the part, ensure to place the concave side of the membrane towards the actuator plate H and the reference hole indicated in the seat I ( fig. 66 Removal of the switch 1. Switch off the boiler; remove the front panel of the case, lower the protection plate and lower the control panel. 2.

  • Page 38: Temperature Probes

    Nominal flow rate (litres/min) Colour Blue To install the flow limiter operate as in the following sequence: 1. Remove the d.h.w. filter as explained in the section 14.2. 2. Unscrew the part B (fig. 69) and remove it from the body of the filter. 3.
  • Page 39 In the boilers with mixed function (c/h + d.h.w.) two temperature probes are assembled, one on the output of the main heat exchanger (main circuit temperature probe) A, (fig. 71 fig. 72) one on its input, before the pump (d.h.w. temperature probe) B (fig.

  • Page 40: By-Pass Valve

    16 By-pass valve 16.1 Function The by-pass valve is located between the c/h water flow and return (A in fig. 74) and its function is that of guaranteeing a minimum flow across the main heat exchanger also if the circulation across the c/h system is completely closed. fig.
  • Page 41 fig. 76 17 Water pressure switch and pump relay 17.1 Function The boiler is equipped with two water pressure switches which are connected to the main (c.h.) water circuit. They have two different operating points and, by switching an electric circuit, they indicate the water pressure by means of the display circuit (fig.

  • Page 42: Flue Fan, Venturi, Air Pressure Switch

    Black 17.2 Checks WARNING: isolate the boiler from the mains electricity supply before removing any covering or component. 1 Switch off the boiler. Remove the front panel of the case, lower the control panel and empty the main circuit. If you need to verify the operating point of the switches, connect a suitable water pressure gauge to a test point of the circuit near the boiler; 2 disconnect the connectors to the pressure switches and measure the electrical resistance between the connections (fig.
  • Page 43 Check of the air pressure switch operation WARNING: isolate the boiler from the mains electricity supply before removing any covering or component. 1 Remove the front panel of the body and the lid of the sealed chamber 2 Disconnect the wires and check the electrical resistance between its connections Between COM and NO the contact must be open.

  • Page 44: Removal Of The Fan

    fig. 80c 18.3 Removal of the fan WARNING: isolate the boiler from the mains electricity supply before removing any covering or component. 1. Remove the front panel of the body and the lid of the sealed chamber; 2. disconnect the connectors A and the earth connection B (fig.

  • Page 45: Removal Of The Air Pressure Switch

    18.4 Removal of the air pressure switch Note that there are two different air pressure switches with different operating values for the 424 S, 424 RS and 428 S boilers. Refer to the short spare parts list for the correct selection of the switch. WARNING: isolate the boiler from the mains electricity supply before removing any covering or component.
  • Page 46 19.2 Checks Check the position of the electrode edges WARNING: isolate the boiler from the mains electricity supply before removing any covering or component. Remove the front panel of the body, the sealed chamber cover and the combustion chamber panel. Check for the correct distance between the metallic edges of the ignition electrodes and refer it to the fig.

  • Page 47: Safety Thermostat

    In order to recognize the electrodes refer to fig. NOTE: the metallic edge of the detection electrode is longer than the one of the ignition electrodes. 20 Safety thermostat 20.1 Function The safety thermostat (A in fig. 86) is a device that senses the temperature of the main circuit water which flows in the outlet pipe of the main heat exchanger.
  • Page 48 The safety thermostat has two parts: the temperature probe C which is fitted on the outlet pipe of the main heat exchanger (fig. 88) and the electric switch D which is fitted in the control panel (fig. fig. 88 fig. 89 20.2 Checks...

  • Page 49: Short Spare Parts List

    WARNING: isolate the boiler from the mains electricity supply before removing any covering or component. Position of probe and integrity Remove the front panel of the case and the sealed chamber cover. Verify the soundness of the fitting between the main circuit pipe and the temperature probe C (fig.

This manual is also suitable for:

Gaia 428 sGaia 424 rs

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