This bundle brings together the Viessmann Vitodens 025-W (Type BPKB-24) gas condensing combi boiler, a reduced-height horizontal flue kit, and an Onyx in-line system protection filter, giving you a complete, ready-to-install heating and hot water package for smaller homes and flats.
At the heart of the bundle is Viessmann's MatriX-Plus cylinder burner, paired with a stainless steel Inox-Radial heat exchanger for long service life and resistance to corrosion. The boiler modulates heat output down to a 1:4 turndown ratio, so it can match its firing rate closely to demand rather than cycling on and off, helping to keep running costs and wear down.
The included reduced-height horizontal flue kit is designed for external wall termination where roof access isn't practical, while the Onyx filter protects the boiler's heat exchanger from magnetite and system debris from day one — a sensible addition on any new boiler installation, particularly where the existing system pipework hasn't been power flushed.
24 kW
DHW Output
20 kW
CH Output (50/30°C)
A Rated
ErP Efficiency
1:4
Modulation Ratio
34 kg
Boiler Weight
2 Yrs
Standard Guarantee
Good to Know
This is the Viessmann Vitodens 025-W, Type BPKB-24 — Viessmann's official model designation for this 5.0–20.0 kW (50/30°C) gas condensing combi boiler (Gas Council No. 47-819-64). It's sold under a range of retailer names including "Vitodens Classic"; the specification below reflects Viessmann's own published technical data for the BPKB-24.
MatriX-Plus Burner
A modulating, fan-assisted premix burner that adjusts output to demand, delivering quiet, efficient combustion across the boiler's full firing range.
Inox-Radial Stainless Steel Heat Exchanger
A stainless steel heat exchanger built for durability and resistance to corrosion, backed by Viessmann's standard boiler guarantee.
Compact, Cupboard-Friendly Design
At just 300mm deep, the boiler is sized to fit inside a standard kitchen cupboard without excessive clearance requirements.
A-Rated Efficiency
Rated A for both space heating and water heating under the ErP energy labelling scheme, supporting lower running costs.
Onyx System Protection Filter
An in-line filter that captures magnetite and system debris before it can reach and damage the boiler's heat exchanger and pump.
Reduced-Height Horizontal Flue Included
A 60/100mm reduced-height horizontal flue kit for external wall termination, supplied complete with wall bezels and a reduced-height elbow.
This is a gas-fired appliance. Installation, commissioning, and any servicing must be carried out by a Gas Safe registered engineer in accordance with Viessmann's installation and service instructions and current UK gas safety regulations.
Frequently Asked Questions
Is this the same boiler sold as the "Vitodens Classic"?
Yes. "Vitodens Classic" is a retailer name used for this model; Viessmann's own designation is Vitodens 025-W, Type BPKB-24, and the specification listed here is taken from Viessmann's official technical documentation for that model.
What size home is this boiler suitable for?
With a 24 kW DHW output and 20 kW heating output at 50/30°C, this model suits smaller homes and flats with modest hot water demand and heating loads, typically 1–3 bedrooms with a single bathroom.
Does the bundle include everything needed for installation?
The bundle includes the boiler, horizontal flue kit, and Onyx protection filter. Depending on the installation, an installer may still need additional items such as isolation valves, a filling loop, condensate drainage materials, and an outside temperature sensor if weather compensation is required.
What does the Onyx filter do and is it required?
The Onyx filter is a 22mm in-line magnetic filter fitted to the heating system pipework, designed to trap magnetite (rust sludge) and debris before it reaches the boiler. It isn't a Viessmann-branded part, but it's strongly recommended on any new boiler installation to protect the heat exchanger, and is required by many manufacturer warranty terms.
What size is the Onyx filter and will it fit my pipework?
The included Onyx filter is 22mm, matching the heating flow and return connection size on this boiler. If your system pipework runs in 28mm, a pipework reducer will be needed either side of the filter, or a 28mm filter should be sourced separately.
Is the flue kit suitable for a vertical (roof) installation?
No. The included flue kit is a 60/100mm horizontal kit for external wall termination. A separate vertical flue kit is needed where the flue must exit through the roof.
How long is the manufacturer's warranty?
The boiler carries a 2-year guarantee as standard, extendable up to 5, 7, 10 or 12 years when registered with Viessmann within the specified timeframe after installation — terms and conditions apply.
BTU & WATT Calculator
Room Dimensions
Room Type
Living Room
Bedroom
Kitchen
Bathroom
Conservatory
Hallway
Glazing Type
Single Glazed
Double Glazed
Triple Glazed
External Walls
0 Wall
1 Wall
2 Walls
3 Walls
4 Walls
Insulation Level
Poor
Average
Good (New Build)
Required Heating
0
Watts
0
BTUs
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