The Baxi 424 Combi 2.1 is a 24kW combi boiler built for compact UK homes that need reliable heating and hot water without a bulky footprint. Part of Baxi's revamped 400 Combi 2.1 range, it is lightweight, quiet and compact enough to fit inside a 290mm deep cupboard, making it a practical replacement boiler for flats, terraces and small-to-medium properties.
Inside, a stainless steel heat exchanger and brass hydraulics are paired with an ErP A energy efficiency rating for both space heating and hot water, so running costs stay low while durability stays high. The boiler runs on natural gas or LPG without needing a separate conversion kit, giving installers flexibility on a single unit code.
Everyday reliability features include a pre-heated condensate trap to guard against freezing in cold weather, a combined pressure relief valve with separate drain for safer, faster drain-downs during servicing, and an external analogue pressure gauge that lets homeowners top up system pressure themselves, cutting down on avoidable call-outs.
10.2 l/min
DHW Flow Rate (ΔT 35°C)
28kg
Installer Lift Weight
7L
Integral Expansion Vessel
5 Yr
Parts & Labour Warranty
Good to Know
This is the 24kW model (424) in the Baxi 400 Combi 2.1 range. The same platform is also available as the 30kW (430 Combi 2.1) and 36kW (436 Combi 2.1) for larger heat and hot water demand — check property size and radiator count before ordering.
Dual Fuel Ready
Works on natural gas or LPG without a conversion kit, so the same unit code covers both fuel types on site.
Compact & Lightweight
At 395 x 700 x 285mm and a 28kg installer lift weight, it fits 290mm deep cupboards and is easy to manoeuvre into place single-handed.
Robust Build
A stainless steel heat exchanger and brass hydraulics are used throughout for long-term corrosion resistance and reliability.
Winter-Ready Condensate
A pre-heated condensate trap reduces the risk of the condensate pipe freezing during cold snaps, helping avoid winter lockouts.
Safer Servicing
The combined pressure relief valve with a separate drain allows a faster, safer boiler drain-down when repairs or servicing are needed.
Smart Control Ready
Compatible with the Baxi uSense 2 Smart Room Thermostat and the Baxi Easy-Flue system for quicker, safer one-person flue installation.
Please Note
Boiler installation, commissioning and any gas or LPG conversion work must be carried out by a Gas Safe registered engineer in accordance with current Building Regulations and Benchmark requirements.
Identification
Manufacturer Part Number (MPN)
7872835
Product Range
Baxi 400 Combi 2.1
GTIN / Barcode
5033313046194
Boiler Type
Gas Combi Boiler
Gas & Efficiency
Fuel Type
Natural Gas or LPG (no conversion kit required)
Inlet Supply Pressure, Natural Gas (nominal)
20 mbar
Maximum Gas Rate, G20 (Qmax)
2.61 m³/hr
Heat Input CH, Max Gross (QnHs)
20.6 kW
Heat Input CH, Min Gross (QnHs)
4.9 kW
Heat Output CH Non-Condensing, Max (Pn)
20 kW
Heat Output CH Non-Condensing, Min (Pn)
4.8 kW
Heat Output CH Condensing, Max (Pnc)
21.8 kW
Heat Output CH Condensing, Min (Pnc)
5.2 kW
Heat Input DHW, Max Gross (QnwHs)
27.4 kW
Heat Output DHW, Max
24 kW
Water Heating Efficiency Class
A
Space Heating Efficiency Class
A
Hydraulic
Maximum DHW Flow Rate (ΔT 35°C rise)
10.2 l/min
Minimum DHW Flow Rate Required
2 l/min
Minimum Operating DHW Pressure Required
0.5 bar
Integral Expansion Vessel Size
7 litres
Maximum CH System Capacity
100 litres
Integral Automatic Bypass
Yes
Electrical
Permanent Live Required
Yes
External Fuse Rating (connection board)
F0.5A L250VP
Integral Boiler-Only Frost Thermostat
Yes
Dimensions & Weight
Front Clearance (operation / servicing)
5mm / 450mm
Installer Lift Weight
28kg
Compatibility & Warranty
Smart Thermostat Compatibility
Baxi uSense 2 Smart Room Thermostat
Flue System Compatibility
Baxi Easy-Flue (internal fit, short & long)
Warranty
5 years parts and labour
What is the output of the Baxi 424 Combi 2.1?
The Baxi 424 Combi 2.1 (MPN 7872835) has a 24kW domestic hot water output, with a condensing central heating output of up to 21.8kW. It suits smaller to medium UK homes with modest hot water demand.
Can this boiler run on LPG?
Yes. The Baxi 424 Combi 2.1 is designed to work on natural gas or LPG without requiring a separate conversion kit, though installation and any fuel-related setup must still be carried out by a Gas Safe registered engineer.
Will it fit in a standard kitchen cupboard?
The boiler measures 395mm (W) x 700mm (H) x 285mm (D) and is designed to fit within a 290mm deep cupboard, making it suitable for typical UK kitchen and utility installations.
What smart thermostat is this boiler compatible with?
The Baxi 424 Combi 2.1 is compatible with the Baxi uSense 2 Smart Room Thermostat, which allows heating schedules to be controlled remotely via a smartphone app.
What warranty does the Baxi 424 Combi 2.1 come with?
It carries a 5-year parts and labour warranty as standard, subject to annual servicing and registration in line with Baxi's terms and conditions.
How does the pre-heated condensate trap help in winter?
The pre-heated condensate trap reduces the risk of the condensate discharge pipe freezing in cold weather, which is one of the most common causes of boiler lockouts during winter.
