Trustpilot

iS Boiler System

i15S i18S i24S i32S i40S

Discover the Benefits of an ATAG System Boiler

If you’re looking for a reliable, high performance heating solution, an ATAG system boiler is a smart choice. Every ATAG boiler comes with a 12 year warranty as standard, with extended options available up to 18 years. Our boilers are always installed by trained ATAG Selected Partners, so you can be confident in the quality of both the product and the installation.

The ATAG iS system boiler is one of the most energy efficient models available in Europe. Designed with simplicity and usability in mind, it’s easy to operate, making it ideal for busy households that want reliable comfort without the fuss.

One of the standout features of our system boilers is the integrated ErP pump. This built-in component automatically adjusts the amount of heat output based on demand. As a result, it helps your boiler run as efficiently as possible, which can lead to ongoing energy savings year after year.

System boilers are often paired with an unvented hot water cylinder. This setup increases your hot water capacity, making it easier to meet the needs of larger households. Since the pump and controls are built into the boiler itself, you also benefit from a compact and tidy installation.

To learn more about our system boilers, visit our Find your perfect boiler page. You can also find your local ATAG installer to discuss your home’s requirements.

Get a Quote Manual Not sure which boiler you require? Key Features Specification

Key features and benefits

compact

Compact dimensions

h700 x w440 x d366 (mm)

compact

Five models available

15kW, 18kW, 24kW, 32kW, 40kW

compact

Up to 18 years warranty

Including all parts and labour

compact

Completely user friendly

with intuitive controls

compact

Quiet in operation

Due to bottom-up modulation

compact

Frost protection

With built-in frost protection

compact

ErP "A" rated

Achieves ErP ‘A’ rating for heating and hot water

compact

Loved by customers

ATAG is the UK’s highest rated boiler brand on Trustpilot

  • A 275 mm (deep) model is available to fit inside kitchen cupboards
  • 12 years warranty as standard with options up to 18 years
  • Control the system via smartphone using the ATAG ONE Zone
  • ATAG iCon stainless steel heat exchanger – with its unique lifetime replacement guarantee
  • Detailed fault codes on LCD display for quicker, more accurate boiler diagnostics
  • Fully compatible with ATAG iSteel cylinder range & the 3 port valve kit
  • Built-in anti-cycling function for improved efficiency
  • Combined condensate and pressure relief valve outlet pipe means less pipework
  • Fully compatible with solar thermal hot water systems and ATAG iSteel twin coil cylinder range
  • Supplied with fixing jig as standard, for rear piping up behind the boiler
  • Factory fitted ErP-ready pump for low electrical consumption and improved efficiency

Specifications

i15S
i18S
i24S
i32S
i40S

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PART NUMBER

BS300158

ERP SEASONAL SPACE HEATING ENERGY EFFICIENCY CLASS

A

ERP SEASONAL SPACE HEATING ENERGY EFFICIENCY (%)

93

CH OUTPUT KW (50/30°C)

14.7

SEDBUK 2009 (%)

89.8

DIMENSIONS (H X W X D) MM

700X440X355

BOILER LIFT WEIGHT WITH JIG (KG)

39

STANDARD WARRANTY (YEARS)

12

LPG CONVERSION KIT AVAILABLE

YES

NOX CLASS

6

INGRESS PROTECTION (IP)

IPPX4D

MAXIMUM EQUIVALENT HORIZONTAL FLUE LENGTH (M) 60/100MM

18

MAXIMUM EQUIVALENT VERTICAL FLUE LENGTH (M) 60/100MM

18

MAXIMUM EQUIVALENT HORIZONTAL FLUE LENGTH (M) 80/125MM

50

MAXIMUM EQUIVALENT VERTICAL FLUE LENGTH (M) 80/125MM

50

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PART NUMBER

BS300118

ERP SEASONAL SPACE HEATING ENERGY EFFICIENCY CLASS

A

ERP SEASONAL SPACE HEATING ENERGY EFFICIENCY (%)

93

CH OUTPUT KW (50/30°C)

17.5

SEDBUK 2009 (%)

89.8

DIMENSIONS (H X W X D) MM

700X440X355

BOILER LIFT WEIGHT WITH JIG (KG)

39

STANDARD WARRANTY (YEARS)

12

LPG CONVERSION KIT AVAILABLE

YES

NOX CLASS

6

INGRESS PROTECTION (IP)

IPPX4D

MAXIMUM EQUIVALENT HORIZONTAL FLUE LENGTH (M) 60/100MM

18

MAXIMUM EQUIVALENT VERTICAL FLUE LENGTH (M) 60/100MM

18

MAXIMUM EQUIVALENT HORIZONTAL FLUE LENGTH (M) 80/125MM

50

MAXIMUM EQUIVALENT VERTICAL FLUE LENGTH (M) 80/125MM

50

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PART NUMBER

BS300124

ERP SEASONAL SPACE HEATING ENERGY EFFICIENCY CLASS

A

ERP SEASONAL SPACE HEATING ENERGY EFFICIENCY (%)

94

CH OUTPUT KW (50/30°C)

23.2

SEDBUK 2009 (%)

89.8

DIMENSIONS (H X W X D) MM

700X440X355

BOILER LIFT WEIGHT WITH JIG (KG)

39

STANDARD WARRANTY (YEARS)

12

LPG CONVERSION KIT AVAILABLE

YES

NOX CLASS

6

INGRESS PROTECTION (IP)

IPPX4D

MAXIMUM EQUIVALENT HORIZONTAL FLUE LENGTH (M) 60/100MM

18

MAXIMUM EQUIVALENT VERTICAL FLUE LENGTH (M) 60/100MM

18

MAXIMUM EQUIVALENT HORIZONTAL FLUE LENGTH (M) 80/125MM

50

MAXIMUM EQUIVALENT VERTICAL FLUE LENGTH (M) 80/125MM

50

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PART NUMBER

BS300132

ERP SEASONAL SPACE HEATING ENERGY EFFICIENCY CLASS

A

ERP SEASONAL SPACE HEATING ENERGY EFFICIENCY (%)

94

CH OUTPUT KW (50/30°C)

31.2

SEDBUK 2009 (%)

89.8

DIMENSIONS (H X W X D) MM

700X440X355

BOILER LIFT WEIGHT WITH JIG (KG)

42

STANDARD WARRANTY (YEARS)

12

LPG CONVERSION KIT AVAILABLE

YES

NOX CLASS

6

INGRESS PROTECTION (IP)

IPPX4D

MAXIMUM EQUIVALENT HORIZONTAL FLUE LENGTH (M) 60/100MM

6

MAXIMUM EQUIVALENT VERTICAL FLUE LENGTH (M) 60/100MM

6

MAXIMUM EQUIVALENT HORIZONTAL FLUE LENGTH (M) 80/125MM

45

MAXIMUM EQUIVALENT VERTICAL FLUE LENGTH (M) 80/125MM

45

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PART NUMBER

BS300140

ERP SEASONAL SPACE HEATING ENERGY EFFICIENCY CLASS

A

ERP SEASONAL SPACE HEATING ENERGY EFFICIENCY (%)

94

CH OUTPUT KW (50/30°C)

38.8

SEDBUK 2009 (%)

89.8

DIMENSIONS (H X W X D) MM

700X440X355

BOILER LIFT WEIGHT WITH JIG (KG)

42

STANDARD WARRANTY (YEARS)

12

LPG CONVERSION KIT AVAILABLE

YES

NOX CLASS

6

INGRESS PROTECTION (IP)

IPPX4D

MAXIMUM EQUIVALENT HORIZONTAL FLUE LENGTH (M) 60/100MM

6

MAXIMUM EQUIVALENT VERTICAL FLUE LENGTH (M) 60/100MM

6

MAXIMUM EQUIVALENT HORIZONTAL FLUE LENGTH (M) 80/125MM

45

MAXIMUM EQUIVALENT VERTICAL FLUE LENGTH (M) 80/125MM

45

3

OneZone

Control the temperature in your home remotely using the ATAG One Zone App, available for FREE on the App Store or Google Play.

OneZone Smart Controller
2

Cylinders

Need replacement cylinders? Check out our range to see which one your boiler requires.

View all Cyclinders
3

Complete Care

Ask your ATAG installer about the complete care pack, including the ONEZone smart controller, to increase your standard warranty from 12 to 18 years.

Find out more

Installers that you can depend on

From design through to installation and after-care service, our ATAG selected gas-safe installers are on hand to offer you excellent advice and the best solution possible that suits your needs.

Find an Installer