Baxi Combi 105e Installation And Servicing Instructions
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Baxi Combi 105e Installation And Servicing Instructions

Baxi Combi 105e Installation And Servicing Instructions

Gas fired wall mounted combination boiler
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Baxi Combi 80e & 105e
Gas Fired Wall Mounted Combination Boiler
Installation and
Servicing Instructions
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Questions and answers

Vince Ellicott
March 15, 2025

Have bled my radiators today, respressurised the system to 1.25 bar but now I **** unable to get heating or hot water - red flashing light (fault on pump or low pressure). As I said I have reset the pressure and don't think there is a fault, it was working yesterday!

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Mr. Anderson
March 15, 2025

If a Baxi Combi 105e has no heating or hot water after bleeding the radiators and repressurizing the system, possible causes include:

1. Airlock in the System – Air trapped in the boiler or pipes can prevent proper circulation.
2. Low System Pressure – Ensure the pressure is at the correct level after repressurization.
3. Safety Thermostat Activation – If the boiler overheated, the safety thermostat may have shut it down. Reset it by turning the selector fully anti-clockwise to the reset position.
4. Flame Failure – If the flame failure light is on, the boiler may not be igniting properly, requiring service.
5. Air Flow Monitor Issue – If the air pressure sensing device detects a problem with the flue system, the boiler may not operate.

If these checks do not resolve the issue, contacting a service engineer is recommended.

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Summary of Contents for Baxi Combi 105e

  • Page 1 Please leave these instructions with the user Baxi Combi 80e & 105e Gas Fired Wall Mounted Combination Boiler Installation and Servicing Instructions...
  • Page 2 Type test for purpose of Regulation 5 certified by: Notified Body 0051. We hope you get a satisfactory service from Baxi. If Product/Production certified by: not, please let us know. Notified Body 0051.

  • Page 3: Table Of Contents

    Contents Section Page Introduction General Layout Appliance Operation Technical Data Dimensions and Fixings System Details Site Requirements Installation Commissioning the Boiler 10.0 Completion 11.0 Servicing the Boiler 12.0 Changing Components 13.0 Illustrated Wiring Diagram 14.0 Fault Finding 15.0 Short Parts List...

  • Page 4: Installation

    Description 1. The Baxi Combi 80e or 105e is a fully automatic gas fired wall mounted combination boiler. It is room sealed and fan assisted, and will serve central heating and mains fed domestic hot water.

  • Page 5: General Layout

    2.0 General Layout Layout Air Pressure Switch Expansion Vessel Burner Manifold Automatic Air Vent DHW Plate Heat Exchanger Circulation Pump Drain Off Point Pressure Relief Valve Optional Integral Timer Central Heating System Pressure Gauge Control Box 3-Way Valve Assembly Spark Generator Flame Sensing Electrode Spark Electrode Burner...

  • Page 6: Appliance Operation

    3.0 Appliance Operation NOTE: All delay timers mentioned in 3.1 and 3.2 Central Heating Circuit are overridden by domestic hot water demand. Central Heating Mode (Fig. 2) 1. With a demand for heating, the pump circulates water through the primary circuit. At a pre- determined flow rate the central heating flow switch operates, initiating the ignition sequence.

  • Page 7: Technical Data

    4.0 Technical Data Combi 80e Appliance Type DHW Circuit NO x Class Pressures Appliance Category CAT II Flue Terminal Diameter 100mm Max Operating 2H 3+ Dimensions Projection 95mm Min Operating Heat Input C/H & DHW (Gross) Min Operating Pressure Connections copper tails at 9.8 l/min 26.3...

  • Page 8: Technical Data - Combi 105E

    4.0 Technical Data Combi 105e Appliance Type DHW Circuit NO x Class Pressures Appliance Category CAT II Flue Terminal Diameter 100mm Max Operating 2H 3P Dimensions Projection 95mm Min Operating Heat Input C/H & DHW (Gross) Min Operating Pressure Connections copper tails at 12.7 l/min 0.96...

  • Page 9: Dimensions And Fixings

    5.0 Dimensions and Fixings Dimensions A 780mm B 345mm C 450mm D 107mm Ø Min. E 200mm F 190mm G 143mm 360° Orientation Tube Ø 100mm Tap Rail 65 mm 65 mm 65 mm 65 mm 65 mm Heating Pressure Relief Heating Domestic Hot Cold Water...

  • Page 10: System Details

    6.0 System Details Information 1. The Baxi Combi 80e and 105e Combination Boilers are ‘Water Byelaws Scheme - Approved Products’. To comply with the Water Byelaws your attention is drawn to the following installation requirements and notes (IRN). a) IRN 001 - See text of entry for installation requirements and notes.
  • Page 11 6.0 System Details System Filling and Pressurising 1. A filling point connection on the central heating return pipework must be provided to facilitate initial filling and pressurising and also any subsequent water loss replacement/refilling. Double Stop 2. There are connection points on the mains cold Check Stop Valve...
  • Page 12 6.0 System Details Other Tap Domestic Hot Water Circuit (Fig. 6) Outlets 1. All DHW circuits, connections, fittings, etc. Boiler Expansion should be fully in accordance with relevant Vessel standards, the Water Supply (water fittings) Regulations and the Water Bylaws (Scotland). 2.

  • Page 13: Site Requirements

    WARNING - The addition of anything that may 200mm Min interfere with the normal operation of the appliance without the express written permission of Baxi UK Limited could invalidate the appliance warranty and infringe the G (Installation Fig. 7 AFETY...
  • Page 14 7.0 Site Requirements Ventilation of Compartments 1. Where the appliance is installed in a cupboard or compartment, no air vents are required. 2. BS 5440: Part 2 Clause 4.2 refers to room sealed appliances installed in compartments. The appliance will run sufficiently cool without ventilation.
  • Page 15 7.0 Site Requirements Flue 1. The flue terminal position must be in accordance with the current editions of B.S. 5440 Part 1, and either Part J of the Building Regulations England and Wales or Part F of the Building Standards (Scotland) Regulations as appropriate.
  • Page 16 7.0 Site Requirements Flue Dimensions The standard horizontal flue kit allows for flue lengths between 100mm and 1m from elbow to terminal (Fig. 12). The maximum permissible equivalent flue length is: 5 metres 105e 4 metres NOTE: Each additional 45° of flue bend will Fig.
  • Page 17 7.0 Site Requirements 7.12 Flue Options 1. The Baxi Combi 80e and 105e can be fitted with flue systems as illustrated. 2. The standard flue is suitable only for horizontal applications. Maximum Length = 3m inc. 2 x 45° bends 3.

  • Page 18: Installation

    NOTE: A small amount of water may drain from the boiler in the upright position. Fig. 17 Central Heating Return Baxi UK Limited declare that no substances harmful to health are contained in the appliance or used during construction of the appliance.
  • Page 19 Wall Plate 8.0 Installation Fitting The Boiler 1. Remove the sealing caps from the boiler connections. 2. Lift the boiler using the lower edges. Engage the slots at the top rear of the boiler on the wall plate (Fig. 18). 3.
  • Page 20 8.0 Installation Wall Thickness Fitting The Flue HORIZONTAL FLUE 1. The standard flue is suitable for lengths 100mm minimum to 1m maximum (measured from the edge of the flue elbow outlet). 80e model only If the optional rear flue kit is to be used, refer to the instructions supplied.
  • Page 21 (see Section 7.10 & 7.11). Fig. 24 VERTICAL FLUE 1. Only a flue approved with the Baxi Combi 80e and 105e can be used. Clip 2. For information on vertical flues consult the Baxi Combi Installer Guide or Notes for Guidance supplied with the vertical flue pack.
  • Page 22 8.0 Installation Making The Electrical Connections To connect the mains input cable proceed as follows:- 1. Slacken the facia securing screws and lift the outercase panel so that its locating tabs are clear of the facia. Remove the panel. Control Box Cover 2.

  • Page 23: Commissioning The Boiler

    Commissioning the Boiler Commissioning the Boiler Screw 1. Reference should be made to BS 5449 Section 5 when commissioning the boiler. 2. Open the mains water supply to the boiler. Automatic 3. Open all hot water taps to purge the DHW Air Vent system.

  • Page 24: Checking The Burner Pressure

    Commissioning the Boiler Pressure Test Point Sealing Screw Checking the Burner Pressure 1. Turn on the gas and electrical supplies to the boiler and ensure that all external controls are Gas Valve calling for heat. 2. Set the temperature controls to maximum and the selector switch to the Off position (Fig.

  • Page 25: Completion

    10.0 Completion 10.1 Completion Case Front Panel 1. Hinge the facia panel upwards and refit the case front panel. Secure them with the screws previously removed (Fig. 37). 2. Instruct the user in the operation of the boiler and system, explaining the operational sequence. 3.

  • Page 26: Servicing The Boiler

    11.0 Servicing the Boiler 11 .1 Annual Servicing Case Front Panel 1. For reasons of safety and economy, it is recommended that the boiler is serviced annually. Servicing must be performed by a competent person. 2. After servicing, complete the relevant section of the “Benchmark”...
  • Page 27 Baffle 11.0 Servicing the Boiler Spring Clip 11.1 Annual Servicing (Cont) 10. Remove the spring clips retaining the air box side baffle plates. Disengage the tabs on the baffles from the slots in the fan hood (Fig. 42). 11. Undo the screws securing the fan and hood to the appliance back panel.

  • Page 28: Changing Components

    12.0 Changing Components IMPORTANT: When changing components Pressure ensure that both the gas and electrical Switch supplies to the boiler are isolated before any work is started. When the new component has been fitted turn the selector switch fully anticlockwise against the spring pressure to Sensing position R and hold for 2 seconds to reset the Tubes...
  • Page 29 12.0 Changing Components 12.3 Heat Exchanger (Fig. 48) Heat Exchanger 1. Note the positions of the two sensing tubes on (80e model) the outlet elbow and three wires on the fan motor and remove them. 2. Slacken the screws on the outlet sealing collar. Ease the collar upwards as far as possible.

  • Page 30: Changing Injectors/Electrodes/Insulation

    12.0 Changing Components Injector Inlet Elbow Manifold 12.5 Injectors (Fig. 50) 1. Remove the burner as described in Section 12.4. 2. Undo the screws securing the injector Gasket manifold to the inlet elbow and remove the manifold. 3. Unscrew and replace injectors as required Injector and examine the sealing gasket, replacing as necessary.
  • Page 31 12.0 Changing Components 12.8 Gas Valve (Fig. 52) 1. Undo the nut on the gas feed pipe under the boiler. 2. Remove the securing screws and hinge the facia panel down. Gas Valve 3. Disconnect the earth wire and pressure sensing pipe from the valve.
  • Page 32 12.0 Changing Components 12.12 Pump - Head Only (Fig. 54) 1. Drain the primary circuit and remove the socket head screws securing the pump head to the body and draw the head away. 2. Undo the screw on the pump wiring cover and remove the cover.
  • Page 33 12.0 Changing Components 12.15 Pressure Gauge (Figs. 57 & 58) 1. Drain the primary circuit and undo the nut on the pressure gauge capillary. 2. Remove the timer cover and ease the timer wiring aside. Undo the screws securing the gauge retaining bracket.
  • Page 34 12.0 Changing Components 12.18 Pressure Relief Valve (Fig. 61) 1. Drain the primary circuit. 2. Disconnect the discharge pipe from the valve. Using a suitable hexagon key undo the grub screw sufficiently to release the valve. 3. Note the orientation of the valve, rotate it and withdraw it from the manifold.
  • Page 35 12.0 Changing Components Plate Heat Exchanger 12.21 Plate Heat Exchanger (Fig. 64) 1. Drain the primary circuit. 2. While supporting the heat exchanger undo the screws securing it to the brass manifolds. 3. Withdraw the heat exchanger upwards and to the left of the gas valve, taking care not to damage any wires or controls.
  • Page 36 12.0 Changing Components Central Heating Pressure Differential Microswitch / Bracket 12.22 Diverter Valve Assembly (Cont) Valve Sensing Pipe Pressure Differential Valve (Fig. 67) 1. Remove the pressure differential valve as described above. By-pass Pipe Diaphragm 2. From the brass diverter manifold undo the nut on the heating flow pipe.

  • Page 37: Illustrated Wiring Diagram

    13.0 Illustrated Wiring Diagram Air Pressure Switch Central Heating Temperature Sensor Domestic Hot Water Temperature Sensor Domestic Hot Water Flow Priority Pressure Switch Hydraulic Differential Pressure Switch Pump Control PCB Flame Sensing Electrode Mains Input Link Fuse Overheat Stat Gas Valve Spark Generator - brown - green...

  • Page 38: Fault Finding

    14.0 Fault Finding Carry out initial fault finding checks 1. Check that gas, water and electrical supplies are available at the boiler. Electrical supply = 230V ~ 50 Hz. CH water system pressurised to 0.5 bar when the boiler is cold. The preferred minimum gas pressure is 19.5mbar (natural gas), 27mbar (butane) or 36mbar (propane).
  • Page 39 14.0 Fault Finding Domestic Hot Water - Follow operational sequence Turn selector to Replace diaphragm Go to section ‘A’ neon illuminated Is mains water DHW flow valve filter and differential diaphragm damaged assembly clean? Turn thermostat to DHW flow rate more than DHW flow valve rod max.
  • Page 40 14.0 Fault Finding Fault Finding Solutions Sections A to E Is there 230V at: Main terminals L and N Check electrical supply Main terminal fuse Replace fuse neon Replace PCB illuminated Selector terminals a & b Check wiring and a & 3. PCB - A4 Replace selector connector terminals 4 &...
  • Page 41 14.0 Fault Finding Check and correct if necessary 1. Electrical and pressure tube connections Replace air 2. Blockage of pressure tubes pressure switch 3. Restriction in flue 4. Venturi Gas at burner Ensure gas is on and purged PCB - A1 connector has 230V AC Replace gas valve across terminals 2 &...
  • Page 42 14.0 Fault Finding Ensure that mains input terminal L is Live (230V) and N is Neutral (0V) Check and correct if necessary 1. Flame sensing electrode and lead connections 2. Electrode position Replace PCB Flame current should be 1 µA approx. Replace flame sensing electrode Overheat thermostat operated Allow to cool.

  • Page 43: Short Parts List

    15.0 Short Parts List Short Parts List G.C. Description Manufacturers Part No. E66 383 Fan 80e 248001 E66 527 Fan 105e 248002 393 974 Pressure Switch 247380 E66 393 Heat Exchanger 80e 248016 E66 535 Heat Exchanger 105e 248017 E66 398 Burner 80e 248029 E66 399...

  • Page 44: After Sales Service

    Comp N 247938 - Iss 5 - 5/02 After Sales Service 08706 096 096 Technical Enquiries 08706 049 049 Baxi UK Limited Brownedge Road Bamber Bridge Preston Lancashire PR5 6SN www.baxi.com 921.660.3...

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