Bosch 24I RSF User Manual
WALL MOUNTED COMBINATION BOILER FOR CENTRAL HEATING
AND MAINS FED DOMESTIC HOT WATER
N.G. 47 311 37 L.P.G. 47 311 38
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 23.4 kW (80,000 Btu/h)
THESE INSTRUCTIONS APPLY IN THE UK ONLY
THESE INSTRUCTIONS ARE TO BE LEFT WITH THE USER OR AT THE GAS METER
This appliance must be installed by a competent person in accordance with the Gas Safety (Installation and Use) Regulations 1994
Installation Requirements . . . . . . . . . . . . . . . . . . . . . . . . .
General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Siting the Appliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Siting the Flue. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7. Sealed System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8. Open Vent System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9. Hot Water Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10. Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 9 11. Installing the Appliance . . . . . . . . . . . . . . . . . . . . . . . . . . Page 11 12. Commissioning the Appliance . . . . . . . . . . . . . . . . . . . . Page 16 13. Instructions to the User . . . . . . . . . . . . . . . . . . . . . . . . . . Page 18 14. Inspection and Service. . . . . . . . . . . . . . . . . . . . . . . . . . . Page 18 15. Replacement of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 20 16. Conversion Instructions. . . . . . . . . . . . . . . . . . . . . . . . . . Page 23 17. Operational Flow Diagrams. . . . . . . . . . . . . . . . . . . . . . . Page 24 18. Fault Finding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 26 19. Component Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 34
1.1Gas Safety (Installation and Use) Regulations, October 1994 all gas appliances must be installed by a competent person in accordance with the above regulations. Failure to install appliances correctly could lead to prosecution.
1.2The manufacturers notes must not be taken, in any way, as overriding statutory obligations.
1.3The compliance with a British Standard does not, of itself, confer immunity from legal obligations. In particular the installation of this appliance must be in accordance with the relevant requirements of the following;
Gas Safety (Installation and Use) Regulations 1994 as amended. Current IEE Wiring Regulations BS 7671.
Local Building Regulations.
Building Standards (Scotland)(Consolidation). Bylaws of the local Water Company.
Health and Safety Document No. 635 (Electricity at Work Regulations).
The British Gas Material and Installation Specification for central heating and hot water
It should be in accordance with the relevant recommendations of the following British Standards.
BS6798:1987 Specification for installation of gas fired hot water boilers of rated input not exceeding 60 kW.
BS5449:1990 Central Heating for Domestic Premises. BS5546:1990 Installation of gas hot water supplies for domestic purposes.
BS5440:1:1990 Flues and Ventilation for gas appliances of rated input not exceeding 60 kW: Flues.
BS5440:2:1989 Flues and Ventilation for gas appliances of rated input not exceeding 60kW: Air Supply.
BS6891:1988 Installation of low pressure gas pipework installations up to 28mm (R1).
BS7593:1993 Central Heating system cleansing and flushing. BS5482:PART 1 Domestic Butane and Propane gas burning installations in permanent dwellings.
1.4To ensure that the installation will perform to the highest standards, the system and components should conform to any other relevant British Standards in addition to those mentioned in the instructions.
1.5The appliance complies with the Essential Requirements of the Gas Appliance Directive and other Directives currently applicable.
1.6This appliance contains no asbestos products.
There is no potential hazard due to the appliance being electrically unsafe.
There are no substances used that are a potential hazard in relation to the COSHH Regulations 1988.
1.7 The advice and instructions given in this document covers, as far as possible, the foreseeable situations which may arise. Contact Worcester Heat Systems Technical Helpline for advice on specific installations.
2.1This appliance is not suitable for external installation.
2.2The appliance controls are set to provide a maximum output of 23.4 kW for the domestic hot water and central heating load.
2.3The control circuit provides direct burner ignition. A pilot is not used.
2.4PRINCIPAL APPLIANCE COMPONENTS.
See Fig. 1.
A low thermal capacity Gas to Water heat exchanger incorporating an integral Hot Water heat exchanger to provide domestic hot water.
Fully modulating controls in the central heating and domestic hot water modes of operation.
An expansion vessel, pressure gauge and pressure relief valve. A fixed
A Temperature safety
A standard telescopic horizontal flue assembly giving flue lengths from 127mm to 350mm.
Optional extra extension flue kits to provide for flue lengths up to 2500mm.
An optional vertical flue kit to provide for flue lengths up to 3000mm including vertical flue terminal.
Optional facia mounted mechanical programmer.
Fig. 1. Water flow diagram.
gas to water
Sealed system expansion vessel
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
The gas meter and supply pipes must be capable of supplying this quantity of gas in addition to the demand from any other appliances being served. The table below gives an indication of limiting gas pipe lengths and the allowance to be made for fittings. Refer to BS6891 for further information.
The complete installation, including the gas meter, must be tested for soundness and purged. Refer to BS 6891.
Total length of gas supply pipe
Note: Each fitting used in the gas line from the meter is equivalent to a length of straight pipe which must be added to the straight pipe length to give the total length.
i.e.: Bend = 0.5 metres, Tee = 0.5 metres, 90° Bend = 0.3 metres.
The appliance and flue components are packaged separately.
2.8 GENERAL INSTALLATION
The appliance is for connection to a sealed system only.
The specified ventilation openings made into a wall or compartment door must not be obstructed.
If the appliance is to be fitted into a compartment then the compartment must conform to the requirements of BS 6798: 1987: Section 7.
Do not place anything on top of the appliance.
The clearances specified for servicing must be maintained.
The appliance has a
The standard telescopic flue assembly length is from 127mm to 350mm.
Extension flue lengths available are from 350mm to 2500mm. An optional vertical flue kit to provide for flue lengths up to 3000mm including vertical flue terminal.
A terminal guard, Type K2, GC 393 553, is available from Tower Flue Components, Vale Rise, Tonbridge, TN9 1TB.
Do not allow the flue terminal fitted to the outside wall to become obstructed or damaged.
A kit for internal fixing of the flue is available separately.
The electronic control system and gas valve modulate the heat input in response to the domestic hot water temperature and central heating setting between minimum and maximum.
The Central Heating Temperature control knob provides for the selection of domestic hot water only (Turned fully
A facia mounted programmer is available as an optional extra. A remote mounted programmer may be connected to the appliance.
There is provision for the connection of a mains voltage room thermostat and/or a frost thermostat.
The electronic controls prevent rapid cycling of the appliance in the central heating mode.
2.11SYSTEM NOTES IMPORTANT
Check that no dirt is left in either the gas or water pipework as this could cause damage to the appliance. The heating system should be flushed and treated in accordance with the recommendations of BS 7593:1992. Thoroughly flush cold water mains supply and purge the gas supply before finally connecting the appliance.
The water pipe connections throughout a sealed system must be capable of sustaining a pressure of up to 3 bar.
Radiator valves must conform to the requirements of BS 2767:1991.
The relief valve discharge must be directed away from any electrical components or where it would cause a hazard to the user.
A drain cock to BS 2879 must be fitted to the lowest point of the system.
For circuit design purposes it is important that due note is taken of the information given in Table 3, section 3 relating to the available pump head.
2.12SHOWERS, BIDETS, TAPS AND MIXING VALVES
Hot and cold taps and mixing valves used in the system must be suitable for operating at mains pressure.
Thermostatically controlled shower valves will guard against the flow of water at too high a temperature.
Hot and cold mains fed water can be supplied direct to an overrim flushing bidet subject to local Water Company requirements. With all mains fed systems the flow of water from the individual taps will vary with the number of outlets operated simultaneously and the cold water mains supply pressure to the property. Flow balancing using
2.13 SAFETY CONSIDERATIONS
The appliance must not be operated in a waterless condition. The appliance must not be operated with the boiler inner casing cover removed.
Work must not be carried out on the appliance without the gas and electricity supplies being switched off.
Checks must be made to ensure that the ventilation openings made into walls and partitions are unobstructed and the correct size.
Domestic Hot Water: With a demand for hot water the burner will light at its maximum setting and then automatically adjust its output to maintain the temperature of the delivered water. When hot water is no longer required, the burner will extinguish. The fan and pump may continue to run for a short period to dissipate the residual heat from the appliance.
Central Heating: With a demand for heating the burner will light at its minimum setting and gradually increase to give a controlled temperature rise. When the required heating temperature is achieved the output of the appliance is then automatically adjusted to maintain the temperature of the system. The output can reduce down to a minimum of 7.5 kW. If the system no longer requires even the minimum output to maintain the desired room temperature the burner will extinguish. The fan and pump may continue to run to dissipate the residual heat from the appliance. The appliance will remain off for a fixed period before
Domestic Hot Water and Central Heating: The appliance will supply heat to the central heating system as required. A demand for domestic hot water at a tap or shower will override the central heating requirement for the period of the domestic hot water demand. When hot water is no longer required the appliance will return to the central heating state and its normal mode of operation. The fan may continue to run to dissipate the residual heat from the appliance as necessary.
2.15 DOMESTIC SUPPLY
Devices capable of preventing the flow of expansion water must not be fitted unless separate arrangements have been made.
3. Data Tables
The data plate is fixed to the inner casing cover.
NOMINAL BOILER RATINGS
HORIZONTAL FLUE (Side or Rear)
WALL HOLE DIAMETER
WALL HOLE DIAMETER (using internal flue fitting kit)
STANDARD FLUE – MINIMUM LENGTH
STANDARD FLUE – MAXIMUM LENGTH
EXTENDED FLUE – MAXIMUM LENGTH
AVAILABLE PUMP HEAD
MIN. FLOW RATE
FLOW AND RETURN
CENTRAL HEATING FLOW FITTING
CENTRAL HEATING RETURN FITTING
COLD WATER MAINS INLET FITTING
DOMESTIC HOT WATER OUTLET FITTING
GAS INLET FITTING
PRESSURE RELIEF VALVE DISCHARGE FITTING
15 mm Copper Tube
OVERALL HEIGHT (including flue turret)
960mm (37.8 inches)
800mm (31.5 inches)
450mm (17.7 inches)
360mm (14.2 inches)
PRIMARY WATER CAPACITY
MAXIMUM COLD SUPPLY PRESSURE
10 Bar (150 psi)
MINIMUM COLD SUPPLY PRESSURE (working) for max. hot water flow
MINIMUM COLD SUPPLY PRESSURE (working) to operate appliance
MAXIMUM CENTRAL HEATING FLOW TEMPERATURE
Nominally 82°C (180°F)
OUTPUT TO DOMESTIC HOT WATER
Modulating 7.5 to 23.4 kW
OUTPUT TO CENTRAL HEATING
Modulating 7.5 to 23.4 kW
MAXIMUM DOMESTIC HOT WATER FLOW RATE (from the appliance)
Nominally 8.0 ± 15% litres/min
EQUIVALENT DOMESTIC HOT WATER FLOW RATE TO GIVE A TEMP RISE
Nominally 11.2 litres/min
OF 30°C (SPECIFIC RATE)
4.Siting The Appliance
4.1The 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.
Where a room sealed appliance is installed in a room containing a bath or shower, any electrical switch or appliance control using mains electricity must not be able to be touched by a person using the bath or shower.
4.2The appliance is not suitable for external installation.
4.3The appliance does not require any special wall protection.
4.4The wall must be capable of supporting the weight of the appliance. See Table 4.
4.5The following clearances must be available for installation and for servicing. See Fig. 2. (note the clearances at the front are for a removable panel e.g. a door).
4.6The appliance can be installed in a cupboard used for airing clothes provided that the requirements of BS 6798 and BS 5440:2 are strictly followed.
In front to a fixed surface
Notwithstanding the instructions given in BS 5440:2, this appliance may be fitted in a compartment with no vents as long as the minimum clearances stated in Section 6: Air Supply, are maintained.
4.7The airing space must be separated from the boiler space by a perforated
4.8No combustible surface must be within 75mm of the casing. See BS476:4.
4.9Always consider the possible need to disconnect the pipes from the appliance after installation.
4.10LPG Installation: The appliance shall not be installed in a room or internal space below ground level when it is intended for use with LPG. This does not preclude the installation into rooms which are basements with respect to one side of the building but open to ground level on the opposite side.
Fig. 2. Appliance casing dimensions and required clearances.
* Space required for installation and servicing
5. Siting The Flue
See Fig. 3.
5.1The flue must be installed as specified in BS 5440:Part 1.
5.2The terminal must not cause an obstruction nor the discharge cause a nuisance.
5.3If 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.
5.4If a terminal is fitted less than 2 metres above a surface to which people have access then a guard must be fitted. See Section 2.9.
5.5The terminal guard must be evenly spaced about the flue terminal and fixed to the wall using plated screws.
5.6In certain weather conditions a terminal may steam and siting where this could cause a nuisance should be avoided.
5.7Take care to ensure that combustion products do not enter ventilated roof voids.
6. Air Supply
6.1 The appliance does not require a separate vent for combustion air.
6.2 The appliance can be fitted in a cupboard with no vents for cooling but the minimum clearances must be increased to those given below (note the clearances at the front are for a removable panel e.g. a door).
Above the Turret
6.3If the appliance is to be fitted in a cupboard or compartments with less clearance than those above (minimum clearances given in Section 4. Siting The Appliance) then permanent vents for cooling are required. One at high level and one at low level, either direct to outside air or to a room. Both vents must pass to the same room or be on the same wall to the outside air.
6.4The minimum free areas required are given below.
6.5 Refer to BS 6798 and BS 5440:2 for additional information.
Fig. 3. Siting of the flue terminal.
A– directly below an openable window or
From a terminal facing a terminal
other opening e.g. air brick.
From an opening in a car port (e.g. door
B– Below gutters, soil pipes or drain pipes.
window) into dwelling.
Vertically from a terminal on the same
D– Below balconies or car port roof.
From vertical drain pipes and soil pipes.
Horizontally from a terminal on the same
From internal or external corners.
G– Above ground, roof or balcony level.
M– From door, window or air vent (achieve
H– From a surface facing a terminal.
7. Sealed System
See Figs. 4.
7.1The system must comply with the requirements of BS 6798 and BS 5449.
7.2The appliance must not be operated without the system being full of water, properly vented and pressurised.
7.3The pressure relief valve operates at 3 bar (45lb/in2). The discharge must be directed away from electrical components or where it might be a hazard to the user.
7.4The pressure gauge indicates the system pressure which must be maintained.
7.5The 8 litre expansion vessel is charged to 0.5 bar and is suitable for a static head of 5 metres (17.5ft). The pressure can be increased if the static head is greater than 5 metres (17.5ft).
7.6With an initial system pressure of 0.5 bar, a system capacity of up to 100 litres can be accommodated. For system capacities greater than this an extra expansion vessel must be fitted. Refer to BS 7074 Pt. 1 for more information. The charge pressure can be increased but with a consequent decrease in system volume.
7.7The filling point must be at low level. See Fig. 4.
7.8Water loss must be replaced. See Fig 4. The connection should be made in the central heating return as close to the appliance as possible.
7.9Repeated venting loses water from the system. It is essential that this water is replaced and the system pressure maintained.
7.10Connections to the mains water supply must not be made without the authority of the local Water Company.
7.11The pump is set at maximum and must not be adjusted.
7.12Connections in the system must sustain a pressure of up to 3 bar.
7.13Radiator valves must conform to BS 2767:10.
7.14Other valves used should conform to the requirements of BS 1010.
7.15The appliance is fitted with a fixed internal
8. Open Vent System
The appliance is NOT suitable for connection to an open vented system.
Fig. 4. Sealed primary water system.
NOTE: A drain cock should be installed at the lowest point of the heating circuit and beneath the appliance.
Automatic air vent
Fixed spindle type
Filling Loop Detail
9.Hot Water Supply
9.1The following are general requirements and, if necessary, reference should be made to the local Water Company before fitting the appliance.
9.2MAINS COLD WATER INLET. Devices capable of preventing the flow of expansion water must not be fitted unless separate arrangements have been made.
A mini expansion vessel kit is available which contains the necessary parts for fitting an internal expansion vessel to the appliance.
See Section 19 COMPONENT PARTS LIST.
A thread sealant compatible with potable water must be used. An external expansion vessel may be fitted on the mains cold water connection to the appliance.
9.3The final 600mm of the mains cold water connection to the appliance should be made in copper tube only.
9.4The appliance is suitable for a mains pressure of up to 10 bar (150 lb/in2).
9.5The appliance is fitted with a mains supply isolating valve.
9.6The maximum domestic hot water flow rate is 8.0 litres/min (±15%) (1.8 gallons/min).
9.7In winter (when the mains inlet water temperature is lower) a reduced flow rate at the taps may be required to achieve the type of hot water delivery temperature available in warmer weather.
9.8It is suggested that long pipe runs to the taps or shower should be insulated to prevent the rapid cooling of domestic hot water after a tap or shower has been turned off.
9.9Hot and cold taps and mixing valves used with this appliance must be suitable for operating at mains pressure and temperatures of 65°C.
9.11Thermostatically controlled or pressure equalising shower valves will guard against the flow of water at too high a temperature.
9.12The 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. Alternatively the shower must be fitted with an
9.13The supply of hot and cold mains water direct to a bidet is permitted, (subject to local Water Company requirements), provided that the bidet is of the
9.14LIME SCALE. In temporary hard water areas (more than 350mg/litre or 200ppm calcium bicarbonate) it is recommended that a proprietary scale reducer is fitted in the mains cold water connection to the appliance. Consult the local water company for additional advice.
Installation of a scale inhibitor assembly should be in accordance with the requirements of the local Water Company. An isolating valve should be fitted to allow servicing. The water hardness can be determined by reference to the local Water Company.
9.15NOTE: HOT WATER ONLY.
If required the appliance may be used for Hot Water only before the Central Heating is connected. A 22mm copper bypass pipe at least 4 meters long must be connected between the Central Heating Flow and Return, but it is advisable to connect a small radiator instead.
IT IS NOT RECOMMENDED TO USE THE BOILER IN THIS CONDITION FOR EXTENDED PERIODS.
Fig. 5. 230V room thermostat connections.
RN RI RL
Fig. 6. 230V programmer connections.
CN CI CL
10.1 MAINS SUPPLY.
230 V ~, 50 Hz, 180 watts.
External Fuse: 3A. Internal Fuses: 2AT HRC(F1), and 1.AF (F2).
10.2It must be possible to completely isolate the appliance.
10.3The following connection alternatives must be used:
A 3 amp fused
10.4The appliance must be earthed.
10.5Mains Cable. 0.75mm2 (24 x 0.20mm) to BS 6500 Table 16. The mains cable must be connected into the terminal X1, marked L (Brown or Red lead), N (Blue or Black lead) and the earth stud and be held securely in the cable clamp. For access undo the three bottom screws and remove the facia access cover. See Fig. 7.
10.6The wiring between the appliance and the electrical supply shall comply with current IEE Wiring Regulations and any local regulations which apply.
10.7If a room thermostat and/or external programmer is to be fitted refer to Figs 5 and 6. The devices must be suitable for use with mains voltage.
10.8A facia mounted mechanical programmer is available as an optional extra. Instructions are supplied with the programmer kits.
10.9A time switch or programmer can be fitted externally to the appliance.
10.10The boiler provides automatic frost protection, the use of a frost thermostat is not recommended. However if an external frost thermostat is considered necessary then it must be used in
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.
After installation or in the event of an electrical fault the electrical system shall be checked for short circuits, fuse failure, incorrect polarity of connections, earth continuity and resistance to earth.
Fig. 7. Mains electricity connections.
Strain relief clamp
Programmer and room thermostat
strain relief clamps
Fig. 8. Wiring diagram.
Flame sense electrode
CH Safety sensorlimit
Fig. 9. Functional flow diagram.
Air pressure switch
Pins3 & 4
DHW temp. sensor
Pins8 & 9
Pins5,6 & 7
Pins1 & 2
Pins19 & 20
CH temp. sensor
CH control POT
Pins 15 & 16
LOW VOLTAGE ELECTRONICS (Microcontroller)
3 2 1
X4 Pin 1
X4 Pin 3
X3 Pin 1
X3 Pin 2
X5 Pin 3
X5 Pin 1
X5 Pin 2