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Ultimate₂ regular (open vent) boiler

Exclusive regular (open vent) boiler with 5 years warranty*

  • ErP A rated for efficiency - to reduce energy bills
  • £15 reward when registered through Club Energy
  • Lightweight boiler with cupboard fit dimensions
  • FREE 5 year warranty with option to extend*

High performance, lightweight boiler

The Ultimate₂ is Glow-worm’s high performance, ErP A rated boiler range developed for the one off installer market, and exclusively manufactured for City Plumbing Supplies.

The Ultimate₂ regular (open vent) boiler is designed for homes with a high hot water demand and is available as a 25kW model. The Ultimate₂ regular model is lightweight for easy installation, and is so flexible it can be sited inside a kitchen cupboard thanks to its compact dimensions.

Designed using an automotive grade, aluminium heat exchanger, the Ultimate₂ offers proven reliability and performance whilst being light to install and also easy to maintain. The model also offers flexible flue options for easy siting, and a modern, bright, LCD display with a simple-to-use interface.

The complete Ultimate₂ range (including combi, system and regular options) is compatible with the full range of Glow-worm controls including the popular MiGo app based control.

The Ultimate₂ offers installers a £15 reward and comes with a free 5 year warranty when registered through Club Energy; where installers can also benefit from business tools including the Plumbing Toolbox app, Gas Safe Notifications, Benchmark and some great rewards.

Features & benefits

  • Regular 25 kW output with small, compact, cupboard-fit dimensions
  • Modern, bright, LCD display with easy-to-use interface
  • High quality, automotive grade, aluminium heat exchanger providing excellent performance
  • High efficiency, A rated boiler for ErP energy labelling to reduce energy bills
  • Uses familiar Glow-worm diagnostics for easy install & servicing
  • Compatible with full range of Glow-worm controls, flues and accessories
  • Ideal for use with Glow-worms innovative MiGo app based control
  • 5 years parts and labour guarantee with option to extend*
  • Telescopic flue option available
  • ø60/100 and ø80/125 flue options available
  • Wide range of Glow-worm accessories available including spacing frame and pipe cover plate
  • Plume Management kit compatible

*When registered through Club Energy



Ultimate₂ system boilerUnit25s
Casing dimensions (H x W x D)mm740 x 418 x 300
Weight (lift)kg32
CH output minimum/maximumkW6.1/25.5
SEDBUK rating 2009 89.3
NOx class (natural gas) 5
LPG compatible No
ErP rating A
Heat exchanger materialAluminium/Stainless steelAluminium
Burner type Pre-mixed
Fully modulating Yes
DHW plate heat exchanger Yes
Integrated hydrobloc Yes
Suitable for sealed systems Yes
Inbuilt filling loop Integrated
Inbuilt condensate trap/siphon Yes
Inbuilt boiler frost protection 2 Stage
Zero compartment ventilation Yes
Pump Grundfos
Top (from top of boiler)mm300
User interface
User display Super Bright LCD
Diagnostics Advanced
User adjustable CH temperature control Yes
Water connectionsmm2 x 22/2 x 15
Maximum horizontal Ø60/100m9
Maximum vertical Ø60/100m9
Maximum horizontal Ø80/125m25
Maximum vertical Ø80/125m25
Optional flume management kit Ø60/100 Yes
Optional spacing frame Yes

*See manual for clearance if side panels are to be removed to assist future service and maintenance

** 5mm if removable panel/door

Related Products

Related Products

Climapro₂ RF Control

Climapro₂ RF

  • Two channel wireless programmable room thermostat
  • Backlit display provides advanced user control and functionality
  • Capable of room and weather compensation*
  • Simple to use handheld unit

Introducing MiGo

The personal heating assistant

  • Wi-Fi thermostat and easy-to-use app
  • Manage heating and hot water from anywhere
  • Reduces energy consumption, saves money
  • Internet weather compensation
  • eBUS communication

Climastat room thermostat

  • Easy to use
  • Extra low voltage
  • Simple & discreet 2 wire connection
  • Polarity not important

Climapro₁ control

Available wireless and wired

  • Annual service reminder function
  • Automatic update for summer and winter
  • Simple and discreet
  • Weather compensation ability (when used with optional outdoor sensor)



Alternative products

Alternative products

Ultimate₂ combi boiler

Exclusive combi boiler with 5 years warranty*

  • Leading combi boiler offering great performance
  • FREE 5 year warranty* with option to extend
  • £15 reward when registered through Club Energy
  • Available in 30kW and 35kW models

Ultimate₂ system boiler

Exclusive system boiler with 5 years warranty*

  • ErP A rated for efficiency - helping to reduce energy bills
  • FREE 5 year warranty with option to extend*
  • £15 reward when registered through Club Energy
  • Available as 25kW model