Baxi Combi Instant 80 HE Installation & Servicing Instructions Manual
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Baxi Combi Instant 80 HE Installation & Servicing Instructions Manual

Baxi Combi Instant 80 HE Installation & Servicing Instructions Manual

Gas fired wall mounted condensing combination boiler
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Installation & Servicing Instructions
Baxi Combi Instant 80 HE
Baxi Combi Instant 105 HE
Gas Fired Wall Mounted
Condensing Combination Boiler
Please leave these instructions with the user

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Nigel Stephens
June 26, 2025

is the vertical flue on a 80 HE Instant compatible with a new 824

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Summary of Contents for Baxi Combi Instant 80 HE

  • Page 1 Installation & Servicing Instructions Baxi Combi Instant 80 HE Baxi Combi Instant 105 HE Gas Fired Wall Mounted Condensing Combination Boiler Please leave these instructions with the user...

  • Page 2: Natural Gas

    Notified Body 0051. success. Product/Production certified by: Notified Body 0051. We hope you get a satisfactory service from Baxi. If not, For GB/IE only. please let us know. Baxi is a BS-EN ISO 9001 Accredited Company This product has an energy rating (B) on a scale of A to G.
  • Page 3 Contents Section Page Legislation 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: Legislation

    (see section 6.2). conditions. Codes of Practice, most recent version should be used “Benchmark” Log Book As part of the industry-wide “Benchmark” initiative all Baxi boilers now include an In GB the following Codes of Practice apply: Standard Scope Installation, Commissioning and Service Record Log Book.

  • Page 5: Introduction

    1.0 Introduction Description Case Front Panel 1. The Baxi Combi Instant 80 HE or 105 HE is a fully automatic gas fired wall mounted condensing combination boiler. It is room sealed and fan assisted, and will serve central heating and mains fed domestic hot water.

  • Page 6: General Layout

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

  • Page 7: Appliance Operation

    Central Heating Mode 3.0 Appliance Operation NOTE: All delay timers mentioned in 3.1 and 3.3 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 20 22 the ignition sequence.
  • Page 8 3.0 Appliance Operation Domestic Hot Water Mode Domestic Hot Water Mode (Fig. 4) 1. Priority is given to the domestic hot water supply. A demand at a tap or shower will override any central heating requirement. 2. The flow of water will operate the DHW flow switch which requests the 3 way valve to change position.

  • Page 9: Technical Data

    Installation Lift Weight Fuse 2A Fast Blow to BS 4265 65°C Pre-heat ON ± 5°C dependent upon flow rate SEDBUK Declaration For Combi Instant 80 HE Pump - Available Head The seasonal efficiency (SEDBUK) is 87.3% (89.3% LPG) Band B This value is used in the UK Government’s Standard Assessment...
  • Page 10 4.0 Technical Data Combi Instant 105 HE Appliance Type Power Consumption 180W Central Heating Primary Circuit Pressures Appliance Category CAT II 2H 3P Electrical Protection IPX5D Safety Discharge Heat Input CH NO x Class Max Operating Min Operating Condensate Drain 1”...

  • Page 11: Dimensions And Fixings

    5.0 Dimensions and Fixings Dimensions A 780mm B 345mm C 450mm D 116mm Ø Min. E 185mm F 190mm G 131mm 360° Orientation Tube Ø 100mm Tap Rail 28mm Condensate Drain 65 mm 65 mm 65 mm 65 mm 65 mm Heating Heating Domestic Hot...

  • Page 12: System Details

    6.0 System Details Information 1. The Baxi Combi Instant 80 HE and 105 HE Condensing 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).
  • Page 13 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 Stop Check 2. There are connection points on the mains cold water Valve Valve Valve...
  • Page 14 6.0 System Details Other Tap Domestic Hot Water Circuit (Fig. 8) Outlets 1. All DHW circuits, connections, fittings, etc. should be Boiler Expansion fully in accordance with relevant standards, the water Vessel supply regulations. 2. Your attention is drawn to: for GB: Guidance G17 to G24 and recommendation R17 to R24 of the Water Check Regulations Guide.

  • Page 15: Site Requirements

    7.0 Site Requirements 20mm/5mm Min see *NOTE: 450mm 5mm Min Location 1. The boiler may be fitted to any suitable wall with the 200mm Min flue passing through an outside wall or roof and discharging to atmosphere in a position permitting satisfactory removal of combustion products and providing an adequate air supply.
  • Page 16 7.0 Site Requirements Ventilation of Compartments 1. Where the appliance is installed in a cupboard or compartment, no air vents are required as the appliance will run sufficiently cool without ventilation. Gas Supply 1. The gas installation should be in accordance with the relevant standards.
  • Page 17 7.0 Site Requirement Termination to an internal soil and vent pipe Boiler Condensate Drain FAILURE TO INSTALL THE CONDENSATE DISCHARGE PIPEWORK CORRECTLY WILL AFFECT THE RELIABLE OPERATION OF THE BOILER The condensate discharge pipe MUST NOT RISE at any point along its length. There MUST be a fall of AT LEAST 2.5°...
  • Page 18 7.0 Site Requirements Flue NOTE: Due to the nature of the boiler a plume of water vapour will be discharged from the flue. This should be taken into account when siting the flue terminal. 1. The following guidelines indicate the general requirements for siting flue terminals.
  • Page 19 7.0 Site Requirements Flue Dimensions The standard horizontal flue kit allows for flue lengths between 100mm and 685mm from elbow to terminal (Fig. 14). The maximum permissible equivalent flue length is: Instant 80 HE 4 metres Instant 105 HE 3 metres NOTE: Each additional 45°...
  • Page 20 7.0 Site Requirements 7.11 Flue Options 1. The Baxi Combi Instant 80 HE and 105 HE can be fitted with flue systems as illustrated. 2. The standard flue is suitable only for horizontal applications. 3. Maximum permissible equivalent flue lengths are:-...

  • Page 21: Installation

    1. Connect a tube to the central heating flow or return pipe (Fig. 17). 2. Flush thoroughly (see System Details, Section 6.2). 3. The use of the optional Baxi Filling Loop Kit (Part No. 248221) will simplify the flushing and soundness checking.
  • Page 22 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 23 8.0 Installation Fitting The Flue HORIZONTAL FLUE 1. The standard flue is suitable for lengths between 100mm minimum and 685mm maximum, as measured from the edge of the flue elbow outlet to the joint between the terminal and air duct (Fig. 20). 2.
  • Page 24 11. Fit the flue trim if required, and if necessary fit a terminal guard (see Section 7.9 & 7.10). VERTICAL FLUE 1. Only a flue approved with the Baxi Combi 105 HE can be used. 2. For information on vertical flues consult the Baxi Flue Guide brochure.
  • Page 25 8.0 Installation Making The Electrical Connections To connect the mains input cable proceed as follows:- 1. Slacken the facia panel securing screws and lift the outercase panel so that its securing tabs are clear of the facia. Remove the panel. 2.

  • Page 26: 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 Air 3. Open all hot water taps to purge the DHW system. Vent 4.
  • Page 27 Commissioning the Boiler Burner Pressure Test Point Sealing Screw Checking the Burner Pressure Inlet Pressure Test 1. Turn on the gas and electrical supplies to the boiler Point Sealing Screw and ensure that all external controls are calling for heat. Gas Valve 2.

  • Page 28: Completion

    10.0 Completion 10.1 Completion Case Front Panel 1. Hinge the facia panel upwards and refit the case front panel. Tighten the securing screws (Fig. 38). 2. Instruct the user in the operation of the boiler and system, explaining the operational sequence. 3.

  • Page 29: Servicing The Boiler

    11.0 Servicing the Boiler Case Front Panel 11 .1 Annual Servicing 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 30 Baffle 11.0 Servicing the Boiler Spring Clip 11.1 Annual Servicing (Cont) 11. Ease the front edge of the left hand baffle upwards, disengaging the spring clip. Disengage the tab on the baffle from the slot in the fan hood (Fig. 42). 12.

  • Page 31: Changing Components

    12.0 Changing Components IMPORTANT: When changing components ensure Pressure that both the gas and electrical supplies to the Switch 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 position R and hold for 2 seconds to Sensing reset the boiler before recommissioning.
  • Page 32 12.0 Changing Components 12.3 Heat Exchanger (Fig. 50) 1. Remove the fan as described in section 12.1. 2. Drain the primary circuit. Prise the three pipe connecting clips off the joints in the flow and return pipes. Remove the heat exchanger return pipe. 3.
  • Page 33 12.0 Changing Components Injector Inlet Elbow Manifold 12.5 Injectors (Fig. 52) 1. Remove the burner as described in Section 12.4. 2. Undo the screws securing the injector manifold to the inlet elbow and remove the manifold. Gasket 3. Unscrew and replace injectors as required and examine the sealing gasket, replacing as necessary.
  • Page 34 12.0 Changing Components 12.8 Gas Valve (Fig. 54) 1. Undo the nut on the gas feed pipe under the boiler. Modulator 2. completely undo the securing screws and hinge the Wires facia panel down. Ignition Lead Gas Valve 3. Disconnect the wires from the valve modulator and the ignition lead from the spark generator.
  • Page 35 12.0 Changing Components 12.12 Pump - Head Only (Fig. 57) 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 36 12.0 Changing Components 12.15 Pressure Gauge (Figs. 60 & 61) 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 Fig.
  • Page 37 12.0 Changing Components 12.18 Pressure Relief Valve (Fig. 64) 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 38 12.0 Changing Components Plate Heat Exchanger 12.21 Plate Heat Exchanger (Fig. 67) 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 39 12.0 Changing Components Diverter Valve Operating Head 12.22 Diverter Valve Assembly (Cont) CH Pressure Differential Valve Diaphragm (Fig. 70) Spring Clip 3-pin Plug 1. Isolate the boiler from the central heating flow and return pipes and drain the boiler primary circuit. Diverter Valve 2.
  • Page 40 12.0 Changing Components Secondary 12.24 Secondary Heat Exchanger (Fig. 73) Heat Exchanger 1. Drain the primary circuit Pipe Connecting Clip 2. Undo the four screws securing the right hand case panel. Remove the panel. Fan Spigot Outlet 3. Prise the connecting clips from the heat exchanger Pipe Clamp return pipe and the boiler return pipe.

  • Page 41: Illustrated Wiring Diagram

    13.0 Illustrated Wiring Diagram Air Pressure Switch Central Heating Temperature Sensor Domestic Hot Water Temperature Sensor Optional Timers Microswitch Microswitch Control PCB Flame Sensing Electrode Diverter Valve Operating Head Mains Input Link Fuse Overheat Stat Flue Stat Pump Gas Valve Condensate Trap - brown...

  • Page 42: 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), or 36mbar (propane). 2.
  • Page 43 14.0 Fault Finding Domestic Hot Water - Follow operational sequence Turn On/Off/Reset selector to position. Go to section ‘A’. neon illuminated. Primary water diverted to Go to section ‘M’. DHW preheating circuit. Go to section ‘L’. Turn preheat control to on. External controls and where Ensure controls are set to Preheating function starts after...
  • Page 44 14.0 Fault Finding Central Heating - Follow operational sequence Turn selector to Go to section ‘A’. neon illuminated. Ensure controls are set to demand and verify the contacts are closed. Turn Central Heating External controls calling for neon flashing thermostat to maximum. heat and where fitted, internal Go to section ‘B’.
  • Page 45 14.0 Fault Finding Central Heating - Follow operational sequence (Continued) Continued from previous page Does the burner remain lit ? CH temperature higher than set point of CH thermostat control. When CH temperature decreases cycle continues. Turn the selector to reset. If regular resetting is required Go to section ‘J’...
  • Page 46 14.0 Fault Finding Fault Finding Solutions Is there 230V at: Main terminals L and N Check electrical supply Main terminal fuse Replace fuse neon Replace main PCB illuminated Selector terminals a & b and a Check wiring & 3. PCB - A4 connector Replace selector terminals 4 &...
  • Page 47 14.0 Fault Finding Fault Finding Solutions Check and correct if necessary 1. Electrical and pressure tube connections Replace air pressure 2. Blockage of pressure tubes switch 3. Restriction in flue 4. Venturi Gas at burner Ensure gas is on and purged PCB - A1 connector has 230V across Replace gas valve terminals 2 &...
  • Page 48 14.0 Fault Finding Fault Finding Solutions 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. Flame sensing electrode position Replace main PCB Flame current should be 1 µA approx.

  • Page 49: Short Parts List

    15.0 Short Parts List Short Parts List G.C. Description Manufacturers Part No. Fan (105) 5112430 Fan (80) 5112627 Pressure Switch (105) 248466 Pressure Switch (80) 5112999 Heat Exchanger 5112431 Burner 248029 Injector (105) 5112376 Injector (80) 248210 E66 408 Electrode Lead 248037 E66 411 Spark or Sensing...
  • Page 50 16.0 Notes...
  • Page 51 16.0 Notes...
  • Page 52 923.612.1 BAX I POTT ER TON A Trading Division of Baxi Heating UK Ltd Brownedge Road Bamber Bridge Preston Lancashire PR5 6UP After Sales Service 08706 096 096 Technical Enquiries 08706 049 049 Website www.baxi.co.uk company Comp N 5111807 - Iss 1 - 06/04...
  • Page 53 User’s Operating Instructions Baxi Combi Instant 80 HE Baxi Combi Instant 105 HE Gas Fired Wall Mounted Condensing Combination Boiler Please keep these instructions safe. Should you move house, please hand them over to the next occupier.
  • Page 54 Notified Body 0051. success. Product/Production certified by: Notified Body 0051. We hope you get a satisfactory service from Baxi. If not, please let us know. For GB/IE only. Baxi is a BS-EN ISO 9001 Accredited Company This product has an energy rating (B) on a scale of A to G.
  • Page 55 Legislation IMPORTANT - Installation, Commissioning, Service & Repair Baxi declare that no substances harmful to health are contained in the appliance or used during appliance This appliance must be installed in accordance with the manufacturer’s instructions and manufacture. the regulations in force. Read the instructions fully before installing or using the appliance.
  • Page 56 1.0 Warnings In an Emergency If a water or gas leak occurs or is suspected, the boiler can be isolated at the inlet valves as follows; 1. Turn off the electrical supply and turn the selector switch on the facia box to the OFF position. Gas Tap 2.
  • Page 57 2.0 Introduction Introduction 1. Your Baxi Combi Instant 80 HE or 105 HE is a gas fired, room sealed, powered flue condensing combination boiler, providing central heating for your home and mains fed domestic hot water to taps and shower. It is fully automatic and does not have a pilot light.
  • Page 58 3.0 Operating the Boiler Operating the Boiler 1. Ensure that the electricity and gas supplies are turned on. Check that the central heating pressure is between 0.5 and 1.0 bar (Fig. 4). 2. Turn the On/Off/Reset selector switch either anti- clockwise from the off position (Fig.
  • Page 59 3.0 Operating the Boiler Temperature Control 1. Central Heating: The central heating hot water flow temperature can be adjusted between 30° C (± 5° C) minimum and 85° C (± 5° C) maximum. 2. Turn the control knob clockwise to increase the temperature (Fig.
  • Page 60 Monitor Neon Sensor Fault Neons Safety 1. Your Baxi Combi Instant 80 HE or 105 HE is fitted Thermostat with additional safety devices, which shut down the Neon boiler in the event of the system, the boiler or the flue overheating.
  • Page 61 3.0 Operating the Boiler Pressure Gauge Central Heating System Pressure 1. The water pressure in the central heating system is indicated by the pressure gauge. 2. With the system cold and the boiler not operating Fig. 18 the pressure should be between 0.5 and 1.0 bar. During Normal Pressure (when cold) operation the pressure should not exceed 2.5 bar, and will normally be between 1.0 and 2.0 (Figs.
  • Page 62 4.0 Clearances and Check List 20mm/5mm Min 450mm see *NOTE: 5mm Min Clearances around the Boiler (Figs. 23 & 24) 1. The minimum clear spaces needed around the boiler 200mm Min measured from the casing are as follows: 200mm Bottom 200mm Left Side Right Side...
  • Page 63 (see back page). Guarantee 1. Your Baxi Combi Instant 80 HE or 105 HE is designed and produced to meet all the relevant Standards. 2. Baxi provide a 12 month guarantee on the boiler. The guarantee operates from the date installation is completed for the customer who is the original user.
  • Page 64 When contacting Baxi Potterton please have the following information to hand: Appliance Name Model Number Serial Number A label giving these details is situated on the rear of the hinged lower door panel attached to the users operating instruction label.

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