Baxi 400 Combi

The Baxi 400 is a brand new boiler from Baxi which is available exclusively from independent merchants.

Available in outputs of 24kW and 28kW, the Baxi 400 is powerful enough to meet the heating and hot water demands of most property sizes. We've designed it to be one of our quietest boilers - and with it's small, lightweight design it can be installed virtually anywhere in your house. The Baxi 400 comes with a 5 year parts and labour warranty for complete peace of mind.

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The Baxi 400 Combi has been shortlisted for Domestic Heating Product of the Year at the Heating and Ventilation News Awards 2017

  • Available in outputs: 24 and 28kw to suit most property types
  • Compact size that can be installed in a 290mm deep cupboard
  • Includes the option to be controlled by your smartphone or tablet
  • Rigid filling loop
  • 5 year warranty as standard*
  • 26kg lift weight making it easy to transport, unpack and install
  • Neater installations for hidden pipework
  • Optional stand off frame
  • Industry leading choice of flue lengths, bends and accessories

*Available until 31st December 2017. Subject to registration and an annual service. Terms and conditions apply.


A: Boiler width = 395mm

B: Boiler height = 700mm

C: Boiler depth = 279mm

D: Side clearance = 5mm

E: Upper clearance = 178mm

F: Lower clearance = 200mm

G: Front clearance = 6mm in operation, 450mm for servicing

Baxi 400 Combi 424 Combi 428 Combi
Sales Code

Boiler only




Concealed User Controls No No
Operating mode selector switch with reset Yes Yes
User adjustable DHW temperature Range - 35° to 60° (±5ºC) Yes Yes
User adjustable CH temperature Range - 25° to 80° (±5ºC) Yes Yes
Temp/status/fault diagnosis display LCD display LCD display
Integral 24 hour mechanical timer combi Optional Optional
Plug-In 24 hour mechanical timer combi Optional Optional
Plug-In receiver 7 day RF thermostat-combi Optional Optional
 Single channel 7 day wired programmable thermostat-combi   Optional Optional 
Single channel wired timer Optional Optional
Room thermostat Optional Optional
Wired outdoor weather sensor Optional Optional
Baxi 200 and 400 stand off kit (7659335) Optional Optional
Multifit filling loop (2498221) Optional Optional
SAP 2009 Annual Efficiency (PCDB/SEDBUK) % 89 89
NOx class 5 5
ErP Product Information
NOx mg/kWh 38 40
Sound Power Level, Indoors LWA dB 48 50
Space Heating Efficiency Class A A
Water Heating Declared Load Profile XL XL
Water Heating Efficiency Class A A
Heat Input CH kW max gross (QnHs) 22.87 27.42
kW min gross (QnHs) 5.44 5.44
Heat Output CH (non condensing) kW (Pn) 20 20
kW (Pn) 4.8 4.8
Heat Output CH (condensing) kW max (PnC) 21.8 21.8
kW min (PnC) 5.2 5.2
Gas supply pipe size (mm) 22 22
Inlet supply pressure (natural gas) mbar (nominal) 20 20
Maximum gas rate (natural gas after 10 mins) m3/hr 2.61 3.06
Mechanical and hydraulic
Heat input domestic hot water (DHW) kW max gross (QnwHs) 27.4 32.1
Heat output domestic hot water kW max 24 28
Maximum DHW flow rate (Delta T @ 35ºC max) l/min 9.8 11.5
Minimum DHW flow rate required l/min 2 2
Minimum operating DHW pressure required bar 0.15 0.15
Maximum DHW system pressure bar 8 8
Safety discharge pressure bar 3 3
Compartment ventilation required No No
Flow / return pipe size (mm) 22 22
Integral expansion vessel Size (litres) 7 7
CH system inhibitor required Yes Yes
Condensate discharge pipe size (mm) 21.5 21.5
Electrical supply Volts/Hz 230V/50Hz 230V/50Hz
Permanent live required Yes Yes
Electrical power cable required core 3 x 0.75 3 x 0.75
Power consumption when firing Watts 84 94
External fuse rating Amps 3 3
Internal fuse rating - Connection board Amps 0.5 0.5
Internal fuse rating - Man PCB board Amps 1.6 1.6
Boiler IP rating (electrical protection) without integral timer fitted Approval category IPX5D IPX5D
Circulating pump exercise feature Yes Yes
Pump overrun Yes Yes
Integral 'boiler only' frost thermostat Yes Yes
Concentric flue system
Standard telescopic concentric flue Length in mm 315-500 315-500
Horizontal concentric (60/100 mm) Max equivalent length (m) 10 10
Reduction per 135° bend (m) 0.5 0.5
Reduction per 93° bend (m) 1 1
Horizontal concentric (80/125mm) Max equivalent length 20 20
Installer lift weight (boiler) Max (kg) 26 26
Gross packaged boiler weight (kg) 30 30


Additional heating and hot water accessories can improve the overall efficiency and performance of your heating system. This could reduce your fuel consumption and your energy bills.

For more information on any of the below accessories please speak to your installer as they will be able to advise you on the controls that are right for you.

  • Baxi plug-In 24 hour single channel mechanical timer
  • Baxi plug-In 7 day single channel digital timer
  • Baxi plug-In receiver 24 hour single channel programmable mechanical room thermostat
  • Baxi plug-In receiver 7 day RF digital single channel programmable room thermostat
  • Baxi single channel wired programmable room thermostat
  • Baxi room thermostat

For more information on the Baxi 400 accessories, click here

You can download product information on the Baxi 400 Combi here:

  • Baxi 200 & 400 Combi installation servicing manual (PDF 6.25MB, 15/09/2016)
  • Baxi 200 & 400 Combi user guide (PDF 6.25MB, 15/09/2016)
  • We don't sell our products directly to consumers which is why our prices aren't on our website.

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