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  4. 28Si
  5. Installation And Servicing Instructions

Worcester 28Si Installation And Servicing Instructions

Summary of 28Si

  • Page 1

    25 s i / 28 s i 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). 25si gc number 47 311 49 (n.G.) cg number 47 311 50 (l.P.G.) 28si gc number 47 311 51 (n.G.) ...

  • Page 2

    1.1 gas safety (installation & use) regulations 1998. It is the law that all gas appliances are installed by a competent person in accordance with the above regulations. Failure to install appliances correctly could lead to prosecution. It is in your interest, and that of safety, to ensure complianc...

  • Page 3

    2.6 controls controls for switching the appliance on or off and for adjusting the ch and dhw temperatures. The ch control knob also switches the ch off and on. A programmable room thermostat or a facia mounted programmer or clock is available. A room thermostat and/or an externally mounted programme...

  • Page 4

    The data plate is fixed to the inner casing cover. 4 3. Technical data maximum available pump head boiler output head min. Flow rate kw metres l/min. °c 8.5 5.9 11.0 11 25 2.0 30.5 12 28 2.0 30.5 13 table 3 flue details horizontal flue mm wall hole diameter external fix 110 internal fix 150 standard...

  • Page 5

    5 gas supply system - based on ng (g20) total length of gas supply pipe (copper) metres 3 6 9 12 gas discharge rate - pressure drop 1mbar. M 3 /h pipe diameter mm 8.7 5.8 4.6 3.9 22 18.0 12.0 9.4 8.0 28 table 7 clearances (mm) installation service above appliance and/or flue elbow 30 30 in frontof a...

  • Page 6

    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. Where a room sealed appliance ...

  • Page 7

    The flue system must be installed following the requirements of bs5440: 1. Standard flue kit length is 330 - 725mm (as measured from the centre of the flue turret) with extension kits for flues up to 2975mm measured from the centre line of the flue turret. The terminal must not cause an obstruction ...

  • Page 8

    The system must comply with requirements of bs6798 and bs5449 and must not be operated without being full of water and correctly pressurised. Refer to fig 8. The pressure relief valve will operate at 3 bar. The discharge pipe must be directed away from any electrics or from where it might be a hazar...

  • Page 9

    It may be necessary to contact the local water company before connecting the appliance. Devices, which would prevent the flow of expansion water, must not be fitted unless separate arrangements have been made. A mini-expansion vessel kit is available as an optional extra. The last 600mm of mains wat...

  • Page 10

    10 fig. 11. Wiring diagram. Fan flame sense electrode air pr essur e swit ch spark electrode spark transformer mains in link control board ch sensor (front of heat exchanger) flow switch st16 2 blue 2 orange 2 brown br own blue blue br own 2 violet white 2 red 2 yellow 2 pink st12 st8 st15 st1 pump ...

  • Page 11

    11 fig. 12. Functional flow diagram. M ains indicat o r on/off swit ch st8 (l s ) st8 (l r ) st8 (n s ) st1 centr e pin st15 pin l rel 1 rel 3 pump fan st12 pin n optional link r oom thermost at tr ansf ormer fuse f2 (1.6a slow) fuse f1 (2a slow) n n st12 pin l live in gr een electr onics electronic...

  • Page 12

    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. 11.2 unpacking remove the appliance from its packaging and check the contents against the packing list. Li...

  • Page 13

    11.7 install the boiler remove the cabinet by unscrewing the screw at the top front and releasing the sides. Lift from the top location. Refer to fig. 18. Check that the gas and water valves are closed. Refer to fig.16. Fit the new seals, in the hardware pack, to the service valves on the manifold. ...

  • Page 14

    If l is greater than 725mm then extension duct kit/s will be required - each kit extends the flue by 750mm up to a maximum of 2975mm. See table below. Extension maximum flue length mm 1 1475 2 2225 3 2975 11.9 measure and cut the ducts. General: cut the ducts as necessary, ensuring that the ducts ar...

  • Page 15

    Note: extension duct measurements do not include the socketed end. Unless specifically instructed the socketed end must not be removed. Fix the flue ducts together before fixing the surrounding air duct, the cut ducts fit into the flue assembly. 11.10 fitting the flue assembly with access to the ter...

  • Page 16

    If more than two extension ducts are needed in any section to achieve the required length then the final section of the assembly must not be less than 325mm without cutting the terminal assembly. Note: the flue duct of the final extension must be 30mm longer than the air duct. Each section must be c...

  • Page 17

    17 fig.29. Facia connections cover facia controls connections cover fixing screw facia bottom panel (clip-on) fig.30. Programmer cover cover panel facia programmer connections fig.33. Facia connections 1 2 3 4 5 6 7 8 9 10 1. Earth screw 2. Mains connection (l n) 3. Fuse f1 4. Mains voltage room the...

  • Page 18

    Benchmark water treatment: for optimum performance after installation, this boiler and its associated central heating system should be flushed in accordance with the guidelines given in bs7593:1992 - treatment of water in domestic hot water systems. Full instructions are supplied with proprietary cl...

  • Page 19

    Remove the clip-on facia bottom cover and controls connections cover. Refer to fig 29. Slide down the access panel to display the mode switch and the adjusting tool. Refer to fig 37. 12.6 checking the burner pressure check that all the radiator valves are open. Check that the system is pressurised a...

  • Page 20

    If the appliance is to be passed over to the user immediately then set the controls to the users requirements. If the appliance is to be left inoperative in frosty conditions then set the programmer, if fitted, to off. Do not turn the electricity or gas supplies off. The appliance will operate under...

  • Page 21

    21 fig.41. Inner case components flue spigot inner casing fan assembly flue hood combustion chamber/flue hood fixing screws heat exchanger combustion chamber fixing screw burner connection burner combustion chamber primary sensor overheat thermostat (at rear) combustion products test point (front ca...

  • Page 22

    Important: turn off the gas and electricity supplies before replacing any components. 15.1 after the replacement of any components always check for gas soundness where relevant and carryout functional checks as described in section 12-commissioning. Any o-ring or gasket that appears damaged must be ...

  • Page 23

    Switch on the gas and electricity supplies. Check for gas tightness at the gas valve inlet. Refer to section12-commissioning for the method of checking the pressures. Check for gas soundness at the gas valve outlet. Adjust the maximum and start pressure [minimum], as necessary, to obtain the require...

  • Page 24

    15.4.6 pressure gauge remove the cabinet and lower the facia panel. Refer to fig 40. Check that the appliance has been fully drained. Withdraw the clip and remove the pressure-sensing head. Refer to fig 50. Unclip the gauge head from its mounting bracket and remove.Refer to fig 49 do not omit the o-...

  • Page 25

    15.4.8 flow switch drain the dhw circuit as described in 15.3 preceding. Remove the cabinet and lower the facia panel. Carefully pull off the connections from the micro-switch. Undo the two union connections on the valve and remove the valve. Refer to fig 52. Do not omit the gaskets when fitting the...

  • Page 26

    15.4.11 transformer remove the cabinet and lower the facia panel as described in section 14, inspection and servicing. Unscrew the four screws and remove the metal cover. Refer to fig 54. Pull out the transformer. Refer to fig 56. 15.4.12 clock/programmer remove the clock/programmer assembly by care...

  • Page 27

    15.4.18 pump check that the primary circuit has been fully drained as described in 15.3 preceding. Release the water connections and remove the pump. Refer to fig 45. Disconnect and transfer the electrical connections to the new pump. Set the pump speed to maximum. Do not forget the gaskets at the c...

  • Page 28

    10 e27-572 flow switch prettl 1 8 717 002 122 0 15 e27-578 water filter prettl 1 8 716 148 410 0 17 e27-580 pressure relief valve altechnic 1 8 716 156 764 0 18 e27-582 pump grundfos 59896603 1 8 716 143 114 0 25 e27-586 pressure gauge inter albion x 32556 1 8 716 142 388 0 26 e27-587 expansion vess...

  • Page 29

    29.

  • Page 30

    30 17. Operational flow diagrams main switch on green light on room thermostat and/or mains programmer (or link) on and electronic facia programmer (if fitted) on and st13 link in and ch control knob on central heating demand ch light on. Pump on. Fan on/ ignition sequence. Burner light on. Three mi...

  • Page 31

    31 fan overrun function active for 3 minutes overrun function above 9°c commence normal central heating mode until temperature reaches 30°c 5°c to 9°c below 5°c no demand and primary temperature below 8°c internal “autofrostat” demand wait in normal off state for 30 minutes run pump for four minutes...

  • Page 32

    Note: this fault-finding information is for guidance only. Worcester heat systems cannot be held responsible for costs incurred by persons not deemed to be competent. The electronic control system for this boiler incorporates four lights on the facia. These are used to show normal operating status. ...

  • Page 33

    33 is the facia on/off switch turned on? `(clockwise) is there a 230v ac live supply across terminal st12 pins l and n has fuse f1 blown? Replace fuse and investigate cause. Suggestions: cable damage, connections to (or faults within) pump, fan, external 230v controls, transformer or board. Turn swi...

  • Page 34

    34 red diode is damaged. Replace control board. (section 15.4.10) is there a link at terminal st13 pins 1 and 2? Is there an electronic programmer at position st5 at right- hand end of board? Replace control board. (section 15.4.10). With ch control knob fully clockwise, does the boiler ignite and a...

  • Page 35

    35 boiler is running in “autofrost stat” mode. See section 17. Replace control board. (section 15.4.10). Note: a damp board could cause this fault. Is the boiler in a very cold environment (less than 5°c)? Fail point f no yes is the boiler fully water pressurised and is all air vented? Rectify fault...

  • Page 36

    36 remove front panel. Reset and restart the boiler. Can a flame be seen through the spy glass? Turn off boiler. Remove inner cover and combustion chamber cover. Are the sense electrode and lead in good condition and is gap correct? Remove multiway connector from board position st16. Is there contin...

  • Page 37

    37 remove multiway connector from board position st16. Test resistance across contacts 17 and 18 (yellow wires). Is it between 1 kohm and 30 kohm? Test resistance across contacts 12 and 13 (red wires). Is it between 1 kohm and 30 kohm? Test resistance across contacts 7 and 8 (brown wires) and 9 and ...

  • Page 38

    38 does the fan run before the fault occurs? Turn off boiler. Is there continuity across the c and no terminals of the air pressure switch (where green wires are fitted)? Remove the fan connector from board position st1 and restart the boiler. Is there mains 230v across the centre (l) and left (n) t...

  • Page 39

    39 light indication during fault not covered by above details. Control board is likely to be wet or damaged or malfunctioning. Check for wet board or connections. Dry and re-use or replace control board. (section 15.4.10). Fail point l hot water temperature always too hot during a demand (not regula...

  • Page 40

    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....

  • Page 41: Bosch Group

    Timeswitch instructions for si range bosch group 8 716 145 228a 01/00 fig. 1. Fig. 2. Gas safety (installation and use) regulations 1984: all gas appliances must be installed by a competent person, in accordance with the above regulations. Failure to install the appliance correctly could lead to pro...

  • Page 42: Bosch Group

    Bosch group vertical balanced flue system installation instructions room sealed non-condensing combination/system boilers and water heaters 24i 47 311 37/38 15sbi 41 311 43/45 28i 47 311 54 24sbi 41 311 44/46 25si 47 311 49/50 9/14 cbi 41 311 50/51 28si 47 311 51/52 14/19 cbi 41 311 52/53 c1 47 311 ...

  • Page 43

    2 the flue system must be installed in accordance with bs 5440: part 1 2000 where applicable. When installed the minimum clearance between the terminal and any adjoining vertical walls or obstructions must be at least 500mm. The terminal must not be installed within 600mm of an openable window, air ...

  • Page 44

    3 2.1. Terminal assembly the overall height of the terminal assembly is 1100mm. Note. A minimum of 300mm shall extend above the surface of the roof. Refer to fig. 2. 2.2. Nominal flue height (no offset). The maximum equivalent flue heights, excluding the flue terminal assembly are: table 2. 24i, 28i...

  • Page 45

    4 3.1. Flue height and offsets. Determine the height of the flue system and if offsets are needed for the system to miss ceiling/roof joists and any other obstruction. Refer to fig. 8. 3.2. Installation of boiler. Refer to the relevant installation and servicing instructions for the fitting of the w...

  • Page 46

    5 3.8. Positioning the flue system it may be necessary to deviate from the following method of installation because of site conditions. However, joints must be sealed and fixed as described. Align the centre of the flue spigot with the ceiling and mark the centre position. Refer to fig. 8. Cut a hol...

  • Page 47

    6 4.1 air and flue duct lengths - no offset for a flat roof measure the distance from the appliance top panel to the outside edge of the hole diameter marked on the inside surface of the roof. This is dimension 'e 1 ' refer to fig. 9. For a pitched roof, measure the distance from the appliance top p...

  • Page 48

    7 4.2 air and flue duct lengths - offset with vertical adapter (90° or, where applicable, 45° bends) 1st vertical section: measure from the top of the flue spigot on the appliance to the centre-line of the horizontal section of the offset. Dimension 'j'. Refer to fig. 10. Duct length = j — 173mm not...

  • Page 49

    8 4.3 air and flue duct lengths - offset without vertical adapter (90° or, where applicable, 45° bends) measure the distance from the centre of the flue spigot on top of the appliance to the centre line of the vertical sections. Dimension d. Refer to fig. 11,12. Duct length: 90° bends = d — 162mm 45...

  • Page 50

    9 air inlet flange weather sealing collar (secure with screw provided and seal with silicone sealant) roof flashing (not supplied) flat roof pitched roof ceiling fire stop spacer note: 45° bends may be applied in any system layout as with 90° bends. Note: for more information on bends in flue see in...

  • Page 51

    Terminal assemblly height 1100mm diameter 106mm smear silicone sealant on this joint. Seal ensure the ducts are correctly located into the socketed joints. Vertical flue adaptor 88mm high. Clamping ring appliance front seal fixing screws note: the flue terminal must be connected a minimum of 55mm ab...

  • Page 52

    11 important: do not forget to fix the fire stop spacer as the assembly of the system proceeds. 5.9 fix the flue terminal assembly fit the roof flashing loosely to the roof. From outside, pass the terminal assembly through the roof flashing. From inside the roof space align the assembly with the air...

  • Page 53

    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....

  • Page 54

    Digital single-channel programmer fitting and operating instructions general information is given in the users instruction leaflet despatched with the appliance and/or on the lighting instruction plate fitted to the appliance. These instructions apply in the uk only these instructions are to be left...

  • Page 55

    Gas safety (installation and use) regulations 1984 : all gas appliances must be installed by a competent person, in accordance with the above regulations. Failure to install the appliance correctly could lead to prosecution. The manufacturers notes must not be taken, in any way, as overriding statut...

  • Page 56

    To replace the programmer follow the preceding instructions. 3 programmer connection fig. 1. St5.

  • Page 57

    4 off twice once on.

  • Page 58

    The programmer controls the operation of the central heating circuit. The domestic hot water is permanently available upon demand and will take priority over the supply of heat to the system during the demand. Pressing the set button repeatedly progresses you through the settings. To reset at any po...

  • Page 59

    The test feature enables you to quickly run through the programme which has been set and check that all is correct with both the programme and the system. Pressing the yes button in response to test? Selects the test mode. Pressing and holding down the yes button starts the clock fast running until ...

  • Page 60

    Temperature control: the central heating water temperature is controlled by the centre knob on the facia. The domestic hot water temperature is controlled by the right hand knob on the facia. Standard programme: to return to the standard programme press the select and + buttons together. Refer to th...

  • Page 61

    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....