Bosch Group 24i RSF WALL MOUNTED COMBINATION BOILER FOR CENTRAL HEATING AND MAINS FED DOMESTIC HOT WATER INSTALLATION AND SERVICING INSTRUCTIONS GC NUMBERS N.G. 47 311 37 L.P.G. 47 311 38 BOILER OUTPUT To Domestic Hot Water – Modulated Control Minimum 7.5 kW (25,600 Btu/h) Maximum 23.4 kW (80,000 Btu/h) To Central Heating – Modulated Control\ Auto Range Rated Minimum 7.5 kW (25,600 Btu/h) Maximum 23.
Contents 1. Installation Requirements . . . . . . . . . . . . . . . . . . . . . . . . . Page 2 2. General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2 3. Data Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 4 4. Siting the Appliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 5 5. Siting the Flue. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 6 6. Air Supply . . . . . . . . . . . . . .
2.5 ELECTRICAL SUPPLY Mains supply: 230V ~, 50 Hz, 180 watts. External fuse: 3A., Internal fuses: 2AT HRC(F1), and 1 AF (F2). 2.6 GAS SUPPLY The boiler requires 2.76 m3/h (97.5 ft3/hr) of natural gas with a calorific value of 37.78 MJ/m3 (1014 Btu/ft3) or 1.07 m3/h (37.8 ft3/hr) of propane with a calorific value of 95.65 MJ/m3 (2568 Btu/ft3). The meter governor should deliver a dynamic pressure of 20 mbar (8in w.g.) at the appliance, equivalent to a pressure of about 19-19.
The data plate is fixed to the inner casing cover. 3. Data Tables Table 1 kW Btu/h 7.5 23.4 (25,600) (80,000) NOMINAL BOILER RATINGS BURNER SETTING INPUT (Net). PRESSURE kW Btu/h m bar. in. wg. NATURAL GAS 9.60 (32,750) 1.0 0.4 26.05 (88,890) 13.6 5.4 7.5 23.4 (25,600) (80,000) 9.60 26.05 OUTPUT GAS RATE 3 m /h ft3/h 1.01 2.76 35.7 97.5 0.39 1.07 13.9 37.8 PROPANE (32,750) (88,890) 3.5 35.0 1.4 14.0 Table 2.
4. Siting The Appliance Fig. 2. Appliance casing dimensions and required clearances. 4.1 The appliance may be installed in any room although particular attention is drawn to the requirements of the current IEE Wiring Regulations BS 7671 and, in Scotland, the electrical provisions of the Building Regulations applicable in Scotland, with respect to the installation of appliances in rooms containing baths or showers.
5. Siting The Flue 6. Air Supply See Fig. 3. 5.1 The flue must be installed as specified in BS 5440:Part 1. 5.2 The terminal must not cause an obstruction nor the discharge cause a nuisance. 5.3 If the terminal is fitted within 850mm of a plastic or painted gutter or within 450mm of painted eaves then an aluminium shield at least 750mm long should be fitted to the underside of the gutter or painted surface. 5.
.7 The filling point must be at low level. See Fig. 4. 7.8 Water loss must be replaced. See Fig 4. The connection should be made in the central heating return as close to the appliance as possible. 7.9 Repeated venting loses water from the system. It is essential that this water is replaced and the system pressure maintained. 7.10 Connections to the mains water supply must not be made without the authority of the local Water Company. 7.11 The pump is set at maximum and must not be adjusted. 7.
9.10 No anti-syphonage arrangements are necessary except for some loose head showers. See also Section 9.11 following. 9.11 Thermostatically controlled or pressure equalising shower valves will guard against the flow of water at too high a temperature. 9.12 The head of a loose head shower must not fall closer than 25mm (1in.) above the top edge of the bath to prevent its immersion in bath water.
conjunction with a programmer. Important: To provide external frost protection the appliance must have the Central Heating Temperature Control Knob set to supply heating (the appliance may then be left with the central heating turned off on the programmer). Connection must be made at X2 terminals RI and CL. For advice on external frost thermostats contact Worcester Heat Systems Technical Helpline 10.11 SAFETY CHECK.
CH control POT DHW temp. sensor CH temp. sensor X6 Pins 3 & 4 Flow signal Outputs X6 Pins 19 & 20 Air pressure switch X6 Pins 1 & 2 Overheat stat X6 Pins 15 & 16 X6 Pins 8 & 9 Modulating valve X6 Pins 5,6 & 7 Fig. 9. Functional flow diagram. Inputs FAN X4 Pin 3 X4 Pin 1 LOW VOLTAGE ELECTRONICS (Microcontroller) RL1 PUMP X3 Pin 1 Mains indicator X3 Pin 2 RL3 X5 Pin 3 GAS VALVE F2 1.
Technical Helpline. Flue components 1. Turret clamping ring. 2. Flue turret assembly 3. Flue terminal assembly 4. Extension air duct 5. Extension flue duct 6. In-line 90° flue bend 7. In-line 45° flue bend 8. Vertical flue adapter The flue must be installed as specified in BS 5440 Part 1. NOTE: READ THIS SECTION FULLY BEFORE COMMENCING INSTALLATION 11.2 GENERAL FITTING.
Measure and cut the extension ducts to length ensuring that the cuts are square and free from burrs. Always check the dimensions before cutting the ducts. All extension duct dimensions refer to the straight lengths. The socketed ends must not be removed or included in any measurement. Connect the gas, water and pressure relief valve connections to the appliance. The primary system should be flushed and treated in accordance with the recommendations of BS7593:1992. Fig. 12. Appliance pipework connections.
Fig. 16. Standard flue assembly. Fig. 18. Flue turret fixing. Flue turret Rear flue L + 181mm Side flue L + 184mm Turret assembly Fixing screw Terminal assembly Appliance casing L Flue Gas Test Point 2. If L is within the range 127mm to 350mm then the flue can be telescopically adjusted to the correct length (L+184mm for side flues or L+181mm for rear flues).
11.5 INTERNAL FITTING OF THE DUCT ASSEMBLY The rubber sealing gasket and the clamping ring are available from Worcester Heat Systems. Measure and cut the ducts as previously described for external fitting (Section 11.4). Fix the ducts to the terminal and fit the rubber sealing gasket and clamp to the terminal. Centralise the gasket and tighten the clamping ring. See Fig. 19. Slide the flue centering ring onto the air duct and tighten the screw. See Fig. 20.
11.7 VERTICAL ADAPTER Measure and fit the flue as in Section 11.6 Flue bends except the first section length is measured from the case top and the ducts are cut to X – 168mm. The minimum length for X is 190mm. See Fig. 22. 11.8 FINAL INSTALLATION Check that all the water and gas connections have been tightened. If a facia mounted programmer is to be fitted follow instructions with the programmer.. Remove the facia bottom panel as described in Section 14.3(c).
12. Commissioning The Appliance Fig. 25. Appliance components and fixings (upper assembly). 12.1 SUMMARY The appliance is dispatched with the controls set to provide a maximum output for domestic hot water and central heating of 23.4 kW (80,000 Btu/h). The appliance automatically modulates to satisfy lower heat loads. Domestic Hot Water and Central Heating Systems. Check that both the mains water supply and central heating systems have been fully flushed out at installation. Gas Service.
12.3 PROGRAMMER Any programmer fitted on the appliance should be set up at this stage following the instructions sent with the programmer. 12.4 APPLIANCE OPERATION Turn off the gas and electricity supplies to the appliance. Undo the two screws and hinge down the facia. Loosen the burner pressure test point screw and connect a pressure gauge. See Fig. 27. Central Heating Check that all the radiator valves are open.
13. Instructions To The User 14. Inspection And Service 13.1 Tell the user how to operate the appliance and hand over the Users Instructions leaflet. 13.2 Tell the user what to do if the heating system is not to be used in frosty weather. 13.3 Tell the user the sealed system set pressure. 13.4 Tell the user of the importance of regular servicing. Worcester Heat Systems Ltd. offer a comprehensive maintenance contract. 13.5 Set the system controls to the user’s requirements. 13.
14.3 DISMANTLE THE APPLIANCE To carry out a full and comprehensive service of the appliance remove the following parts to gain access to the components which need to be checked or serviced. (d) Bottom panel. Unclip and remove the appliance bottom panel. (e) Fan. Remove the inner casing cover. Carefully unplug the electrical connections and pull off the sensing tubes. Unscrew the four fixing screws and remove the fan assembly. See Fig. 30. (f) Combustion Chamber Front. Remove the inner casing cover.
2. Air Pressure Switch. See Fig. 34. Check that the electricity supply to the appliance is turned off. Remove the cabinet front panel as described in Section 14.3 (a) and lower the facia. Section 14.3(c). Carefully pull off the sensing tubes and the electrical connections from the switch. Remember to note their positions. Unscrew the two screws behind the Air Pressure Switch and remove the switch from the appliance.
Restart the appliance in central heating mode and adjust the minimum adjustment screw on the gas valve to give a pressure of 1.0 mbar on natural gas or 3.5 mbar on propane. See Fig. 33. After completing the adjustments, check the minimum and maximum pressures and re-adjust as necessary. Once this has been done the clear cap should be re-fitted to the adjuster and the retaining screw tightened. Coat the screw with paint or nail varnish to prevent user adjustment. 6. Combustion Chamber Insulation.
13. Domestic Hot Water Sensor. Check that the electricity supply to the appliance is turned off. Hinge the facia assembly in the servicing position as described in Section 14.3(c and d). Carefully pull off the two leads from the sensor. Undo and remove the clamping screw. Pull off the sensor and spring retaining clip from the pipe. Fit the replacement sensor in the reverse order ensuring a layer of heat sink compound is between the faces. Refit the leads. 14. Circulating Pump. See Figs. 32 and 34.
20. Control Board. Check that the electricity supply to the appliance is turned off. Undo the 3 screws and remove the facia bottom panel. Remove the two upper screws and hinge down the facia assembly. Carefully pull off all the connectors. Disconnect the mains supply lead at terminal X1 and the earth connection at the back. Remove the four corner screws on the back of the facia and separate the metal back panel from the plastic facia. Remove and retain the brass nut and washer.
Pump on Water flow temperature monitored by central heating sensor Escape pause by resetting the mains electricity supply OFF-ON Is fan in overrun mode? YES NO Wait (pump on in central heating mode) FAIL Air pressure switch test PASS AUTOMATIC START-UP SEQUENCE Internal "Autofrostat" demand CENTRAL HEATING DEMAND Operating Switch (or programmer) and room thermostat on End of a domestic hot water overrun 1.
Inhibit operations for approximately 1 second. 6 second delay before reignition from any other demand. Run pump Burner pressure at 1.
CH control POT DHW temp. sensor CH temp. sensor X6 Pins 3 & 4 Flow signal Outputs X6 Pins 19 & 20 Air pressure switch X6 Pins 1 & 2 Overheat stat X6 Pins 15 & 16 X6 Pins 8 & 9 Modulating valve X6 Pins 5,6 & 7 18. Fault Finding Inputs FAN X4 Pin 3 X4 Pin 1 LOW VOLTAGE ELECTRONICS (Microcontroller) RL1 PUMP X3 Pin 1 Mains indicator X3 Pin 2 RL3 X5 Pin 3 GAS VALVE F2 1.
Fault in Domestic Hot Water Fault in Central Heating Is mains LED flashing? YES GO TO CHECK D YES NO NO Is mains LED illuminated? NO GO TO CHECK C NO Is mains LED iluminated? YES YES Is control knob set for demand? Is mains LED flashing? NO Turn control knob fully clockwise NO Ensure link is fitted at X2 pins 5 & 6 NO Set room stat to call for heat NO Ensure link is fitted at X2 pins 2 & 3 YES Is a room thermostat fitted? YES Is room thermostat calling for heating? YES Is programmer
No mains LED Is mains present at X1 pins 1 & 3? NO Connect mains supply YES Is F1 (2ATHRC) OK? NO Replace fuse YES Is F2 (1.
Overheat Thermostat Check The overheat thermostat can be reset by pressing the reset button, but if it trips immediately or on a regular basis a serious problem has occurred therefore contact your installer Reset thermostat Does button hold in? NO Is capillary broken? YES YES Is capillary firmly ATTACHED to exchanger? NO Replace overheat thermostat ATTACH to heat exchanger YES GO TO CHECK I Pump Check Is pump connector secure on the PCB (X3)? NO Secure Connector YES Is mains present at the pu
Thermistor Check Remove connectors from thermistor YES Is resistance between terminals of thermistor between 690ohms & 33k NO Faulty thermistor YES Thermistor OK Harness Continuity Check Remove appropriate connectors YES Is continuity observed between each end of wire in question? NO Faulty harness or connector YES Harness OK Harness Short Check Remove appropriate connectors YES Is short circuit observed between pair of wires in question? NO Faulty harness YES Harness OK 30
Ignition Check Is fan running? NO GO TO CHECK G NO GO TO CHECK E NO Is sparking present at the electrodes? YES Does sparking occur? GO TO CHECK L Faulty PCB Replace YES Does ignition occur? NO YES YES Are ignition leads connected both ends securely? Are leads breaking down? YES Replace leads NO YES Is flame sense electrode in flame? NO YES Is lead secure both ends? NO YES GO TO CHECK I HARNESS OK Faulty PCB Replace Does gas pressure modulate? NO Connect ignition leads securely NO
L Air Pressure Switch Check Remove BROWN and WHITE terminals from air pressure switch With no demand, is a short-circuit observed at exposed APS terminals? NO Air pressure switch faulty YES Reconnect the WHITE & BROWN wire and remove the GREEN wire. Initiate a demand. Does the fan run? NO YES Fan or fan cable faulty YES With fan running disconnect BROWN wire. (DO NOT touch chassis with it).
N Modulating Valve Check Is minimum pressure observed at burner at all times? YES Remove X6, measure resistance between pins 15 & 16 NO GO TO CHECK I NO Is resistance nominally 125ohms YES Is pressure at burner always the same? YES NO With pressure above minimum, remove Modureg Lead. Does pressure drop to minimum? NO Faulty modulating valve . Replace gas valve Reconnect X6 and measure voltage across modulating valve during operation YES Gas valve OK YES Does voltage go above 6.
19. Component Parts List Key No. 1 G.C. No.
9 8 14 3 21 1 15 22 4 13 12 7 11 10 20 23 23 25 24 2 35 6 19 18 16
Bosch Group Worcester Heat Systems Limited, Cotswold Way, Warndon, Worcester WR4 9SW. Telephone: (01905) 754624. Fax: (01905) 754619. Technical Helpline (0990) 266241. This booklet is accurate at the date of printing but will be superseded and should be disregarded if specifications and/or appearances are changed in the interests of continued improvement. All goods sold are subject to our official Conditions of Sale, a copy of which may be obtained on application.