ATAG insists that their boilers are installed and commissioned to the highest standard and that they take great care regarding how their boilers are installed to ensure you get the maximum benefits from your ATAG boiler. Even boilers manufactured to the highest specification will sometimes encounter an issue.
This article will help you identify your boiler’s error and fault codes so that you can inform your Gas Safe Engineer what the issue is.
Many may not have heard about ATAG boilers, however, they have been designing and manufacturing boilers for almost 70 years. During this time, they have set the highest standard for energy efficiency and engineering excellence across the world.
ATAG feel that they stand out from the rest by operating in many different countries across the world. ATAG claim to offer the most energy-efficient boilers in Europe with the lowest NOx emissions, meaning they’re kinder to the environment.
Fitted in each boiler is an iCon heat exchanger, which maintains 98% of its original efficiency levels throughout its lifetime, helping to lower your energy bills. No wonder so many customers love their ATAG boiler.
ATAG boilers are installed in large commercial buildings, as well as in domestic properties. They are trusted by many to deliver high performance, efficiency, and supreme reliability. This explains why ATAG boilers are the number one boiler choice for professionals such as architects and design engineers. In addition to winning numerous global awards, UK consumers also rate ATAG the number one boiler manufacturer on independent review site Trustpilot.
To learn more about ATAG and its history, you can visit its website.
The benefits of having an ATAG boiler installed:
- Quiet operation
- 4 different boiler models
- Reliable and efficient
- Compact design
- User friendly
- Comes with a standard 10-year warranty but can be extended to 14
When looking at Trustpilot, ATAG has been awarded a fantastic 4.9 stars out of 5 and has over 3.8k reviews. 99% of ATAG’s reviews are above average, showing that although ATAG boilers may not be a well-known boiler brand, those who have an ATAG are more than happy with their performance and reliability.
Here are what ATAG’s customers have had to say about their boilers and ATAG as a brand:
“The boiler has performed noticeably better than our previous condensing boiler and benefitted from valuable technical support from the ATAG Team”.
“Excellent boiler which is very efficient – already saving money on our bills”
“Highly recommended, reliable, easy, economical and good customer service”.
If you are looking for a new or replacement cost-effective boiler, but you’re unsure what boiler model you need, we have listed a few of our other blogs below that may be able to help:
If you suspect an issue with your ATAG boiler, we have provided a list of their fault/error codes that could help you to identify the issue and potentially point it out to your Gas Safe Engineer.

ATAG boiler error codes
Fault Code | System Behaviour |
10 | Outside sensor error |
20 | Flow sensor error |
40 | Return sensor error |
61 | Bus communication error |
78 | Water pressure out of range |
105 | Venting program active when power turn on/ interrupted (runs for 7 mins) |
110 | Exceeded safety temperature |
111 | Exceeded maximum pressure |
119 | X2 link positions 4 and 5 are missing |
129 | Fan doesn’t start |
133 | No flame after 5 ignition attempts |
151 | Fan error or control unit defective (speed control is not achieved) |
154 | Return greater than flow – flow temperature increases too fast |
101 | Overheat error |
102 | Pressure sensor fault |
104 | Flow check failed |
108 | Pressure needs filling |
1P4 | Pressure needs filling to 0.5 – 0.8 bar |
109 | Pressure > Pmax error |
110 | Send probe damaged |
112 | Return probe error – could be damaged |
114 | Outdoor sensor error – could be damaged |
141 | Central heating flow switch is open |
201 | Domestic hot water (DHW) probe damaged |
203 | Tank probe damaged |
303 | Printed circuit board (PCB) error |
304 | Too many resets have occurred |
501 | No flame detected |
612 | Fan fault – fan isn’t starting up |
iC & iS Combi Boiler Error Codes
Fault Code | System Behaviour |
50 | Domestic hot water (DHW) sensor error |
117 | Pressure greater than 3 bar or pump pressure increase is too high |
118 | Pressure less than 1 bar or pump pressure increase too low (no pump detection) |
ATAG Error code 133
If you are seeing the error code 133, your boiler’s flame is failing after 5 ignition attempts. This could be down to your condensate pipe freezing. A frozen condensate pipe is something that is often easily fixed, you can find out how in this guide to defrosting a condensate pipe.
Other Fault Codes
If you see a spanner symbol this could be one of two things:
- Firstly it could mean your boiler is in service mode.
- Secondly, it could be blocking, if the boiler is blocking the code is only temporary and will clear itself or will lock the boiler after several attempts if the error keeps on occurring.
If you’ve reached the end of this blog and still feel like you may benefit more from having a new boiler installed, then get a boiler quote from WarmZilla today! You can get a quote for a brand spanking new boiler in just a few minutes.
All you need to do is answer some simple questions online about your current boiler, your home demands, and we will provide you with a list of suitable boilers for your home. We also offer a Best Price Guarantee, ensuring that we will beat any competitors by £50 if you manage to find a boiler cheaper elsewhere (which you won’t 😉).

Boiler Manuals
- Atag premier
- Atag iC 24
- Atag iC 24 LPG
- Atag iC 28
- Atag iC 28 LPG
- Atag iC 36
- Atag iC 36 LPG
- Atag iC 40
- Atag iC 40 LPG
- Atag iC economiser 27
- Atag iC economiser 27 LPG
- Atag iC economoser 35
- Atag iC economiser 35 LPG
- Atag iC economiser 39
- Atag iC economiser 39 LPG
- Atag iR 12
- Atag iR 12 LPG
- Atag iR 15
- Atag iR 15 LPG
- Atag iR 18
- Atag iR 18 LPG
- Atag iR 24
- Atag iR 24 LPG
- Atag iR 32
- Atag iR 32 LPG
- Atag iR 40
- Atag iR 40 LPG
- Atag iS 12
- Atag iS 12 LPG
- Atag iS 15
- Atag iS 15 LPG
- Atag iS 18
- Atag iS 18 LPG
- Atag iS 24
- Atag iS 24 LPG
- Atag iS 32
- Atag iS 32 LPG
- Atag iS 40
- Atag iS 40 LPG
- Atag blauwe engel
- Atag A200S
- Atag A320S
- Atsg A203C
- Atag A325C
- Atag A325X
- Atag A200SOV
- Atag E22s
- Atag E32S
- Atag E22C
- Atag E32C
- Atag Q 25 S
- Atag Q 38 S
- Atag Q 51 S
- Atag Q 60 S
- Atag Q 25 C
- Atag Q 38 C
- Atag Q 51 C
- Atag XL 70
- Atag XL 110
- Atag XL 140
- Atag XL F 75
- Atag XL F 105
- Atag XL F 125
- Atag XL F 150
- Atag XL F 180
- Atag XL F 210
- Atag XL W 75
- Atag XL W 105
- Atag XL W 125
- Atag XL W 150
- Atag XL W 180
- Atag XL W 210