24i / 28i junior WALL MOUNTED COMBINATION BOILERS FOR CENTRAL HEATING AND MAINS FED DOMESTIC HOT WATER INSTALLATION AND SERVICING INSTRUCTIONS This appliance is for use with Natural Gas or LPG (Cat II 2H3P TYPE C12 & C32) 24i GC NUMBER 47 311 69 (N.G.) GC NUMBER 47 311 71 (L.P.G.) 28i GC NUMBER 47 311 70 (N.G.) GC NUMBER 47 311 72 (L.P.G.) GB/IE APPLIANCE OUTPUTS Worcester, Bosch Group, Cotswold Way, Warndon, Worcester WR4 9SW. Telephone: (01905) 754624. Fax: (01905) 754619.
Contents commissioning procedure to confirm gas soundness and correct boiler operation. 10. Check and adjust the setting pressures to the values in the table overleaf and adjust if necessary. Refer to Installation and Service Instructions Section: Replacement of Parts. “To Set the Burner Pressure”. 20. Conversion Instructions 1. Installation Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TEST G Is the boiler in a very cold environment (less than 5°C)? No 2.3 Electrical Supply 230V - 50Hz. Load 152 watts. External fuse 3A, Internal fuses F1 - 2A, F2 - 1.25A (20mm). Replace control board. Note: A damp board could cause this fault. 2.4 Gas Supply The appliances require a maximum of 3.17 m3/h of natural gas (G20) or 1.23 m3/h of propane (G31) [28i] or 2.74 m3/h of natural gas (G20) or 1.06 m3/h of propane (G31) [24i].
2.11.2 Domestic Hot Water: The appliance can provide domestic hot water whenever it is switched on electrically. A demand for hot water will light the burner. The pressure will immediately rise to maximum. At the end of the demand the fan will continue to run for 35 seconds if there is no heating demand. In winter it may be necessary to reduce the flow at the taps to maintain the delivery temperature.
Is the multiway connector at board position ST16 pushed fully home on to the board? 3. Technical Data No Push fully home Table 1. No Re-fix sensor onto pipe Yes Remove multiway connector from board position ST16. Test resistance across pins 16 and 17 ( yellow wire). Is it between 1 kOhm and 30 kOhm? 7.5 23.
Table 5 PERFORMANCE SPECIFICATIONS PRIMARY WATER CAPACITY litres IP RATING (WHOLE OF BOILER) 24i 3 28i 3 IP 20 IP 20 MAXIMUM MAINS INLET PRESSURE bar 10 10 MINIMUM MAINS INLET PRESSURE (WORKING) FOR MAXIMUM FLOW bar 0.9 0.9 MINIMUM MAINS INLET PRESSURE (WORKING) FOR OPERATION bar 0.1 0.1 DOMESTIC HOT WATER TEMPERATURE RANGE °C 55 55 MAXIMUM CENTRAL HEATING FLOW TEMPERATURE °C 82 (nom) 82 (nom) MAXIMUM CENTRAL HEATING SYSTEM SET PRESSURE bar 2.5 2.
Is the gas supply connected and at the correct pressure? No Fig. 5. Pipework connections Rectify gas supply problem. Yes Remove front panel. Reset and restart the boiler. Can a flame be seen through the spy glass? No Is the boiler fully water pressurised and is all air vented? No Rectify fault Yes Remove inner cover. Reset and restart the boiler.
Notwithstanding the instructions given in BS 5440:2, these appliances can be fitted in a compartment with no vents as long as the clearances specified in Table 8 are maintained. LPG Installation. Refer to Section 1.9. 4. Siting The Appliance The appliance may be installed in any room but refer to the requirements of the current IEE Regulations and, in Scotland, the relevant electrical provisions of the Building Regulations with respect to the installation of appliances in rooms containing baths or showers.
The pump is set at maximum and should not be adjusted. All connections in the system must withstand a working pressure of up to 3 bar. The radiator valves must conform to BS 2767:10 and other valves to BS1010. 6. Air Supply NOTE: It is normal for there to be no facia lights if the boiler is in normal overtemperature condition. Continue this test if this fault occurs when the appliance is cold. 6.1 A separate vent for combustion air is not required. Refer to BS5440:2. Fig 8a - System make up 2 7.
9. Domestic Hot Water 11. Electrical It may be necessary to contact the local Water Company before connecting the appliance. Where back-flow prevention devices, including water meters, are fitted the expansion of hot water into cold water main can be prevented. This can result in a pressure build-up that may cause damage to the boiler and household devices such as showers, washing machines etc.
OVERRUN FUNCTION Fig. 9. Wiring diagram. Overheat cut-off device There is a delay of 6 seconds, pump pulses for 2 seconds, 60 second wait, 2 second pump pulse, 60 second wait, pump pulses for 2 seconds. END DHW DEMAND Fan low speed 35 seconds END CH DEMAND Air Pressure Switch Fan Black 6.3mm tag Common White 4.8mm tag Low Speed Red 2.8mm tag High Speed Fan low speed if primary temp above 85°C until below 80°C.
18. Operational Flow Diagrams 24V programmer (if applicable) Overheat cut-off Flame sense Air pressure switch DHW sensor CH sensor Flow sensor Main valves CENTRAL HEATING FUNCTION MAIN SWITCH ON Room thermostat and/or mains programmer (or link) On AND facia programmer (if fitted) On AND CH control knob On Inputs Indicators Red Outputs CH Control knob Electronics/ microprocessor (Safety Low Voltage) Settings Red Flame detect Error indicator indicator/reset Regulator valve Fig. 10.
12. Installing The Appliance 6 9 1-2 27 NOTE: READ THIS SECTION FULLY BEFORE COMMENCING THE INSTALLATION. 11.1 General The appliance is only suitable for fitting to a sealed system. The flue must be installed as specified in BS5440:1 and the current Building Regulations, and, in Eire in accordance with the current edition of IS813. 10 8 11.2 Unpacking Open the carton and check the contents against the packing list. 10 3-4 Fig. 12. Wall mounting assembly 11.
17. Short Parts List Fig. 15 . Appliance location Fig. 13 . Manifold assembly 1 Fibre Washer 2 4 65 CH Flow 65 65 65 3 DHW Flow Gas DHW Cold * Inlet CH Return Lower fixing screws (2) * Filling loop not shown All dimensions in mm 1. Casing location bracket 2. Appliance location bracket 3. Wall mounting frame 4. Pipe channel Fig. 14 . Facia cover 1 Unscrew the facia fixing screws. Refer to Fig 18. Unhook the panel and lower it into the bottom support lugs. Do not strain the support strap.
Fig. 17 . Relief valve discharge connection Fig. 19. Flue spigot and restrictor Fig. 61. Primary heat exchanger 1 6 1 4 2 5 4 5 ! IMPORTANT 2 3 7 1 2 1. 2. 3. 4. 3 Flue spigot fixing screws Flue spigot Restrictor ring Flue spigot fixing holes 4 8 6 Fig. 20. Standard flue assembly 3 20 Auto Air Vent Remove the complete pump assembly as described in Section 16.18. Take care not to strain the electrical connections. Pull out the clip securing the auto air vent cartridge. Refer to Fig 52.
Fig. 21. Extension duct Terminal assembly L Flue turret assembly Fixing screw Fixing screw casing Fig. 22. Flue duct length - side Terminal assembly L Flue turret assembly Fig. 23.
9 Inlet Water Filter and Flow Restrictor Remove the flow turbine as described in 16.8 preceding. Taking care, remove flow restrictor assembly from the flow turbine. Carefully clean wire mesh by back flushing with water or replace assembly if necessary. Refer to Fig. 55. 12 Clock/Programmer Remove the clip-on facia. Remove the clock/programmer assembly by releasing the clip at the top of the clock/programmer and ease away from the control panel being careful not to pull on the connector lead.
11.14 Completion of the Installation Check that all the gas and water connections on the manifold have been tightened. Undo the two screws and remove the connections cover panel. Refer to Fig. 29. Connect the mains supply lead to the appliance and secure the cable clamp. Refer to Fig. 29. Check that there is sufficient loose lead to allow the release of the facia panel assembly. Connect the earth lead. The earth lead of the mains supply must be longer than the live and neutral leads.
Fig. 47. Spark electrode assembly. 3 Flame Sense Electrode Remove the inner casing cover and the combustion chamber cover. Carefully pull off the lead from the electrode assembly. Remove the burner as described in the text following Unscrew the screw and remove the assembly. Refer to Fig. 48. Fig 31 - Mains Voltage External Controls Connections Fig. 30. Optional programmer connection 7 6 230 V Room Thermostat Connections Fig. 48. Flame sense electrode (rear view) Ns Ls LR spare 5 2 2 1.
Check that the pressure relief valve operates by turning the knob anti-clockwise until it releases. Refer to Fig. 17. Water should be expelled from the discharge pipe. 13. Commissioning The Appliance In Eire additional guidance on commissioning is contained in paragraph 15 of IS 813:2001 13.
Inner Case Cover Unscrew the two screws and lift off. Refer to Fig. 39. Combustion Chamber Cover Unscrew the two screws, lift and pull forward to remove. Refer to Fig. 41. Fan Carefully pull off the electrical connections and the tubes from the airflow-sensing device. Unscrew the three screws and remove the fan assembly. Refer to Fig. 42. Flue Hood Remove the fan. Slide out the hood. Ensure the rear seal is in good condition and secure before replacing the flue hood. Refer to Fig. 43.
NOTE: For flues greater than 725mm without a restrictor the CO2 may be up to 0.5% lower. These figures cover all flue conditions. 14. Hand Over 15.4 Component Access Isolate the electrical supply at the mains and turn off the gas supply at the gas service cock on the appliance before starting any service procedures. Always test for gas soundness after the service has been completed.
