Baxi Duo-tec Combi GA

The Baxi Duo-tec Combi GA boiler uses gas adaptive control, which, together with a wide modulation range of 1:7, contributes to smooth operation which delivers more energy efficiency and reliability.  It is an Energy Saving Trust endorsed product, so you can be sure it meets the highest standards of energy efficiency. 

It is available in outputs of 24kW, 28kW, 33kW and the popular 40kW model, which delivers a higher domestic hot water flow rate for larger properties.

Please note: warranty and purchasing information on this site applies to the UK only. For information on how to buy these products in the Republic of Ireland, please visit Baxi Potterton Myson.

Duo-tec Combi GA

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  • Class leading hot water flow rates for increased comfort and convenience
  • User friendly controls with clear, easy to read display
  • Service due reminder notifies you when the boiler requires a service
  • A wide range of outputs to suit all heating and hot water requirements
  • Compatible with natural gas and LPG
  • Energy Saving Trust endorsed product
  • Aftersales services provided by Baxi Customer Support
  • Frost protection - for greater flexibility of siting in garages and lofts
  • Peace of mind is offered with a 2 year warranty*

* Subject to registration and an annual service

Duo-tec Combi GAA: Boiler width = 450mm

B: Boiler height = 763mm

C: Boiler depth = 355mm

D: Side clearance = 5mm

E: Upper clearance = 175mm

F: Lower clearance = 150mm

G: Front clearance = 5mm in operation, 450mm for servicing


Duo-tec Combi 24 Duo-tec Combi 28 Duo-tec Combi 33 Duo-tec Combi 40
Heat Output CH kW (Max) 20 24 28 33
kW (Min) 3.4 3.8 4.7 5.7
Heat Output DHW Output - kW (Max) 24 28 33 40
Maximum DHW Flow Rate (Delta T @ 35°Max) l/min 9.8 11.5 13.5 16.4
Minimum DHW Flow Rate Required l/min 2 2 2 2
Minimum Operating DHW Pressure Required bar 0.15 0.15 0.15 0.15
SEDBUK 2005 Seasonal Efficiency NG / LPG % 91.1 / 93.2 91.1 / 93.2 91.1 / 93.2 91.1 / 93.2
SEDBUK 2009 Seasonal Efficiency NG / LPG % 88.9 / 91.0 89.0 / 91.0 89.0 / 90.9 88.9 / 90.9
NOx Class (5 being lowest) 1 - 5 5 5 5 5
NOx Emission mg/kw/h 16,1 19,3 17 26.5
CO Emission mg/kw/h 5,1 8 7,5 22.8
Mechanical & Hydraulic Connections
CH Flow / Return Pipe Size (mm) 22 22 22 22
DHW Flow / Inlet / PRV Size (mm) 15 15 15 15
Condensate Discharge Pipe Size (mm) 21.5 21.5 21.5 21.5
  • Pre-plumbing jig, complete with pre-formed copper pipe tails, built in filling loop and 1 metre mains cable to save the installer time and money during installation
  • Automatic set up meaning that the boiler recognises the gas type and sets itself up accordingly
  • Compatible with Multifit flue kits, which provide an industry leading choice of lengths, bends and accessories, allowing for versatile siting
  • Front access to all components for straightforward and quick servicing
  • Service due indicator that you can programme to remind your customer to call you when it's time for their boiler's annual service
  • Free of charge Baxi product training throughout the UK
  • Free Gas Safe notification and warranty registration online, saving you time and money on any Baxi boiler you install through the works loyalty scheme


Additional heating and hot water controls can improve the overall performance of your heating system by as much as 13% (according to ErP Directive drafts), dramatically reducing the amount of fuel you use, and the amount you pay for your energy bill.

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

*Test conducted by independent scientific test house TNO, based on an average household's consumption of 100 litres of hot water per day

You can find out more about the Baxi Duo-tec Combi GA by reading the associated product literature, whether looking for a guide on how to use your boiler's controls, or instructions on how to install a product component.

  • Duo-tec GA installation instructions part 1 (PDF 8.00MB, 09/10/2014)
  • Duo-tec GA installation instructions part 2 (PDF 4.11MB, 09/10/2014)
  • Duo-tec GA brochure (PDF 0.81MB, 09/10/2014)
  • Duo-tec GA user operating instructions (PDF 2.35MB, 09/10/2014)
  • Find an installer or find a boilerWe have Gas Safe Registered installers all over the UK who will be able to give you a quote for the installation of your new boiler. To use our handy find an installer tool, simply enter a few details and we'll do all the hard work for you by contacting them on your behalf.

    The installer will get in touch to arrange a site survey to give you a competitive, no obligation quote.

    Unsure of what type of boiler you need?

    Try our find a boiler tool. It will ask you a few key questions relating to your heating and hot water requirements and recommend a suitable gas boiler.

    For more information about this type of boiler, please use the links below:

    FAQs about combi boilers

    The benefits of a combi boiler

    How combi works

    Brochures & guides

    Download documents about the Baxi Duo-tec Combi GA, from installation information, to brochures and user guides.