Baxi COMBI 224 Manual

These instructions include the Benchmark Commissioning Checklist and should be left with the
user for safe keeping.They must be read in conjunction with the Flue Installation Guide.
United Kingdom
en
Installation and Service Manual
High Efficiency Wall Hung Condensing Gas Boiler
Baxi Combi
224 — 228 — 424 — 428
428 LPG

Dear Customer,
Thank you very much for buying this appliance.
Please read through the manual carefully before using the product, and keep it in a safe place for later reference. In order to
ensure continued safe and efficient operation we recommend that the product is serviced regularly. Our service and customer
service organisation can assist with this.
We hope you enjoy years of problem-free operation with the product.

Contents
1 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1 Benchmark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1.1 Building Regulations and the Benchmark Commissioning Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
1.1.2 The Benchmark Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1.3 Installer Notification Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2 General safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4 Specific safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4.1 Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
1.5 Liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.5.1 Manufacturer's liability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.5.2 Installer's liability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.5.3 User's liability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
2 About this manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2 Additional documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.3 Symbols used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.3.1 Symbols used in the manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.4 Abbreviations/Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3 Technical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1 Homologations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.1 Safety, Performance & Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.2 Certifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.3 Gas category . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.4 Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
3.2.1 Technical information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
3.2.2 Technical parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3 Dimensions and connections/clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.4 Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4 Description of the product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
4.2 Operating principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.2.1 Air-gas adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
4.2.2 Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.2.3 Central heating and domestic hot water production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.3 Main components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.4 Control panel description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.4.1 Description of the keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.4.2 Description of the display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
4.5 Standard delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.5.1 Contents of the carton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.6 Accessories and options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.6.1 Optional accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5 Before installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.1 Installation regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.2 Installation requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
5.2.1 Gas supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
5.2.2 Electrical supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
5.2.3 Hard water area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
5.2.4 Bypass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
5.2.5 System control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
5.2.6 Treatment of water circulating systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.2.7 Showers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
5.2.8 Expansion vessel (CH only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
5.2.9 Pump available head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.2.10 Safety pressure relief valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.3 Choice of the location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.3.1 Location of the boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.3.2 Data plate and service label . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Contents
7696317 - 1 - 21032018 3

5.3.3 Bath and shower rooms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
5.3.4 Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5.3.5 Condensate drain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.3.6 Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
5.3.7 Flue/chimney location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.3.8 Horizontal flue/chimney systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.3.9 Flue/chimney trim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.3.10 Terminal guard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
5.3.11 Flue/chimney deflector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
5.3.12 Flue/chimney accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.4 Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
5.5 Unpacking & initial preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.5.1 Unpacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.5.2 Initial preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.6 Connecting diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.6.1 Filling information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
5.6.2 Domestic hot water circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
6 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
6.2 Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
6.2.1 Fitting the pressure relief discharge pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
6.3 Air supply/flue gas connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
6.3.1 Connecting the flue/chimney . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
6.4 Electrical connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
6.4.1 Panel removal to make electrical connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
6.4.2 Electrical connections of the boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
6.4.3 Connecting a room thermostat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
6.4.4 Connecting & setting outdoor weather sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
6.5 Filling the installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
6.5.1 Flushing the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
6.5.2 Fill the installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
7 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
7.2 Checklist before commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
7.2.1 Preliminary electrical checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
7.2.2 Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
7.3 Commissioning procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
7.3.1 De-Aeration function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
7.4 Gas settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
7.4.1 Check the operational (working gas inlet pressure and gas rate) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
7.4.2 Checking combustion - chimney sweep mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
7.5 Configuring the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
7.5.1 System draining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
7.6 Final instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
7.6.1 Handover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
8 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
8.1 Use of the control panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
8.1.1 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
8.2 Start up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
8.3 Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
8.4 Frost protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
9 Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
9.1 Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
9.2 Information menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
10 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
10.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
10.2 Standard inspection and maintenance operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.2.1 Periodic check and maintenance procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.2.2 Checking the water pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
10.2.3 Checking the expansion vessel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.2.4 Checking the automatic air vent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
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10.2.5 Checking the burner and cleaning the heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.3 Specific maintenance instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
10.3.1 Detection/spark ignition electrode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
10.3.2 NTC flue sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
10.3.3 Flow and return sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
10.3.4 Safety overheat thermostat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
10.3.5 HMI control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
10.3.6 Burner/combustion chamber door assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
10.3.7 Air/gas unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58
10.3.8 Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
10.3.9 Heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
10.4 Hydraulics maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
10.4.1 Expansion vessel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61
10.4.2 Pump - complete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
10.4.3 Auto air vent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
10.4.4 Plate heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
10.4.5 Hydraulic pressure sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63
10.4.6 DHW flow sensor (hall effect sensor) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
10.4.7 DHW flow regulator and filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63
10.4.8 Diverter valve motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
10.4.9 Diverter valve cartridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
10.4.10 Pressure relief valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
11 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
11.1 Error codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
11.2 Fault finding — temporary faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
11.3 Fault finding - permanent faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
11.4 Accessing the information menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
11.5 Reading out operating parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
11.6 Statuses and sub-statuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
12 Decommissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
12.1 Decommissioning procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
13 Spare parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
13.1 Short parts list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
14 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
14.1 Combustion check on small heating systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
14.2 LPG model supplement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75
14.2.1 Technical information - LPG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
14.2.2 Technical parameters - LPG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
14.2.3 Gas Category - LPG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
14.2.4 Setting the gas valve - LPG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76
14.2.5 LPG spare parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
14.3 Benchmark commissioning checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
14.4 Service records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
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1 Safety
1.1 Benchmark
1.1.1 Building Regulations and the Benchmark Commissioning
Checklist
Building Regulations (England & Wales) require notification of the
installation of a heating appliance to the relevant Local Authority Building
Control Department. This can be achieved via a Competent Persons Self
Certification Scheme as an option to notifying the Local Authority directly.
The Health & Safety Executive operates the ’Gas Safe Register’, a
selfcertification scheme for gas heating appliances.
This company is a member of the Benchmark initiative and fully supports
the aims of the programme. Its aim is to improve the standards of
installation and commissioning of central heating systems in the UK and to
encourage the regular servicing of all central heating systems to ensure
safety and efficiency.
Building Regulations require that installations should comply with
manufacturer’s instructions. It is therefore important that the
commissioning checklist is completed by the installer. The relevant section
of Building Regulations only relates to dwellings. Therefore the checklist
only applies if the appliance is being installed in a dwelling or some related
structure.
The flowchart opposite gives guidance for installers on the process
necessary to ensure compliance with Building Regulations.
1.1.2 The Benchmark Scheme
Benchmark places responsibilities on both manufacturers and installers.
The purpose is to ensure that customers are provided with the correct
equipment for their needs, that it is installed, commissioned and serviced
in accordance with the manufacturer’s instructions by competent persons
and that it meets the requirements of the appropriate Building Regulations.
The Benchmark Checklist can be used to demonstrate compliance with
Building Regulations and should be provided to the customer for future
reference.
Installers are required to carry out installation, commissioning and
servicing work in accordance with the Benchmark Code of Practice which
is available from the Heating and Hotwater Industry Council who manage
and promote the Scheme. Visit www.centralheating.co.uk for more
information.
Fig.1 Benchmark
AD-3000725-01
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1.1.3 Installer Notification Guidelines
Fig.2 Installer Notification Guidelines
AD-3000696-01
Choose Building
Regulations Notification
Route
Contact your relevant Local
Authority Building Control
(LABC) who will arrange
an inspection or contact
a government approved
inspector
LABC will record the data
and will issue a
certificate of compliance
‘Gas Safe Register’ will issue a
Building Regulations Compliance
Certificate to the property owner
and inform the relevant LABC
You must ensure that the
certificate number issued by
the ‘Gas Safe Register’ is written
onto the Benchmark Checklist
Scheme Members only
Call ‘Gas Safe Register’ on:
0800 408 5577
or log onto:
www.gassaferegister.co.uk
within 10 days
If you notify via the ‘Gas Safe
Register’, the register will issue
the Building Regulations
certificate on members’ behalf
Complete the
Benchmark Checklist
Install and Commission this
appliance to manufacturer's
instructions
Competent Person's
Self Certification Scheme
Building Control
Complete the
Benchmark Checklist
Install and Commission this
appliance to manufacturer's
instructions
1 Safety
7696317 - 1 - 21032018 7

1.2 General safety instructions
Danger
This boiler can be used by children aged 8 years and above and
by persons with reduced physical, sensory or mental capabilities
or lack of experience and knowledge when they have been given
supervision or instruction concerning the safe use of the device
and understand the resulting risks. Children must not be allowed
to play with the appliance. Cleaning and user maintenance must
not be carried out by children without supervision.
Danger
If you smell gas:
1. Do not use a naked flame, do not smoke, do not operate
electrical contacts or switches (doorbell, light, motor, lift, etc.).
2. Shut off gas supply.
3. Open the windows.
4. Trace possible leaks and seal them immediately.
5. If the gas leak is before the gas meter, contact the supplier
6. Telephone the National Gas Emergency Service on:- 0800
111 999.
Danger
If you smell flue gases:
1. Switch off the boiler.
2. Open the windows.
3. Trace possible leaks and seal them immediately.
Warning
Do not touch the flue gas pipes. Depending on the boiler settings,
the temperature of the flue gas pipes may exceed 60oC.
Warning
Do not touch the radiators for long periods. Depending on the
boiler settings, the temperature of the radiators may exceed 60oC.
Warning
Take precautions with the domestic hot water. Depending on the
boiler settings, the domestic hot water temperature may exceed
65oC.
Danger
Before any work, switch off the mains supply to the boiler.
Caution
After maintenance or repair work, check the entire heating
installation to ensure that there are no leaks.
1.3 Recommendations
Warning
Installation and maintenance of the boiler must be carried out by a
qualified installer in accordance with local and national
regulations.
Warning
If the mains lead is damaged, it must be replaced by the original
manufacturer, the manufacturer's dealer or another suitably skilled
person to prevent hazardous situations from arising.
Warning
Always disconnect the mains supply and close the main gas tap
when working on the boiler.
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Caution
Make sure the boiler can be reached at all times.
The boiler must be installed in a frost-free area.
In the case of a fixed connection to the power cord, you must
always install a main double pole switch with an opening gap of
at least 3 mm (EN 60335-1).
Drain the boiler and central heating system if you are not going
to use your home for a long time and there is a chance of frost.
The frost protection does not work if the boiler is out of
operation.
The boiler protection only protects the boiler, not the system.
Check the water pressure in the system regularly. If the water
pressure is lower than 0.8 bar, the system must be topped up
(recommended water pressure between 1 and 2 bar).
Important
Keep this document near to the boiler.
Important
Casing panels may only be removed for maintenance and
servicing purposes. Refit all panels when maintenance work and
servicing are complete.
Note
Instruction and warning labels must never be removed or covered
and must be clearly legible throughout the entire service life of the
boiler. Replace damaged or illegible instruction and warning labels
immediately.
Note
The boiler must not be modified in any way.
1.4 Specific safety instructions
1.4.1 Handling
General
The following advice should be adhered to, from when first handling the
boiler to the final stages of installation, and also during maintenance.
Most injuries as a result of inappropriate handling and lifting are to the
back, but all other parts of the body are vulnerable, particularly
shoulders, arms and hands. Health & Safety is the responsibility of
EVERYONE.
There is no "safe" limit for one man - each person has different
capabilities. The boiler should be handled and lifted by TWO PEOPLE.
Do not handle or lift unless you feel physically able.
Wear appropriate Personal Protection Equipment e.g. protective gloves,
safety footwear etc.
Preparation
Co-ordinate movements - know where, and when, you are both going.
Minimise the number of times needed to move the boiler - plan ahead.
Always ensure when handling or lifting the route is clear and
unobstructed. If possible avoid steps, wet or slippery surfaces, unlit
areas etc. and take special care on ladders/into lofts.
Technique
When handling or lifting always use safe techniques - keep your back
straight, bend your knees. Don’t twist - move your feet, avoid bending
forwards and sideways and keep the load as close to your body as
possible.
Where possible transport the boiler using a sack truck or other suitable
trolley.
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Always grip the boiler firmly, and before lifting feel where the weight is
concentrated to establish the centre of gravity, repositioning yourself as
necessary. See the "Installation" section of these instructions for
recommended lift points.
Remember
The circumstances of each installation are different. Always assess the
risks associated with handling and lifting according to the individual
conditions.
If at any time when installing the boiler you feel that you may have
injured yourself STOP !! DO NOT "work through" the pain - you may
cause further injury.
IF IN ANY DOUBT DO NO HANDLE OR LIFT THE BOILER — OBTAIN
ADVICE OR ASSISTANCE BEFORE PROCEEDING !
1.5 Liabilities
1.5.1 Manufacturer's liability
Our products are manufactured in compliance with the requirements of the
various Directives applicable. They are therefore delivered with the
marking and any documents necessary. In the interests of the quality of
our products, we strive constantly to improve them. We therefore reserve
the right to modify the specifications given in this document.
Our liability as manufacturer may not be invoked in the following cases:
Failure to abide by the instructions on installing the appliance.
Failure to abide by the instructions on using the appliance.
Faulty or insufficient maintenance of the appliance.
1.5.2 Installer's liability
The installer is responsible for the installation and initial commissioning of
the appliance. The installer must abide by the following instructions:
Read and follow the instructions given in the manuals provided with the
appliance.
Install the appliance in compliance with prevailing legislation and
standards.
Carry out initial commissioning and any checks necessary.
Explain the installation to the user.
If maintenance is necessary, warn the user of the obligation to check the
appliance and keep it in good working order.
Give all the instruction manuals to the user.
1.5.3 User's liability
To guarantee optimum operation of the system, you must abide by the
following instructions:
Read and follow the instructions given in the manuals provided with the
appliance.
Call on a qualified professional to carry out installation and initial
commissioning.
Get your installer to explain your installation to you.
Have the required inspections and maintenance carried out by a
qualified installer.
Keep the instruction manuals in good condition close to the appliance.
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2 About this manual
2.1 General
This manual is intended for the installer of a Baxi Combi boiler.
2.2 Additional documentation
These Installation & Service Instructions must be read in conjunction with
the Flue Accessories Fitting Guide supplied in the Literature Pack.
Various timers, external controls, etc. are available as optional extras. Full
details are contained in the relevant sales literature.
2.3 Symbols used
2.3.1 Symbols used in the manual
This manual uses various danger levels to draw attention to special
instructions. We do this to improve user safety, to prevent problems and to
guarantee correct operation of the appliance.
Danger
Risk of dangerous situations that may result in serious personal
injury.
Danger of electric shock
Risk of electric shock.
Warning
Risk of dangerous situations that may result in minor personal
injury.
Caution
Risk of material damage.
Important
Please note: important information.
See
Reference to other manuals or pages in this manual.
2.4 Abbreviations/Glossary
BS British Standard
CH Central heating
DHW Domestic hot water
GB Great Britain
Hi Lower heating value (LHV)
Hs Higher heating value (HHV)
IE Ireland
PCU PCB for managing burner operation
Pn Nominal output
Pnc Condensing output
PWM Pulse wide modulation
Qn Nominal input
SU Safety PCB
2 About this manual
7696317 - 1 - 21032018 11

3 Technical specifications
3.1 Homologations
3.1.1 Safety, Performance & Quality
This boiler has been assessed by an appropriate Notified Body and shown
to meet the requirements of all Directives and Regulations as applicable.
These Directives and Regulations lay down requirements for the safety
and efficiency of the appliance, together with its design, construction and
use of materials. They also require the production process to be covered
by an approved and monitored system of quality assurance.
3.1.2 Certifications
Tab.1 Certifications
CE certificate number 0085CQ0192
NOx class 6
Boiler type C13, C33
3.1.3 Gas category
Tab.2 Gas category, type and supply pressure
Gas category Gas type Supply pressure (mbar)
I2H G20 20
3.1.4 Standards
Codes of Practice — refer to the most recent version
Tab.3 In GB the following Codes of Practice apply:
Standard Scope
BS 6891 Gas Installation.
BS 5546 Installation of hot water supplies for domestic purposes.
BS EN
12828
Heating systems in buildings.
BS EN
12831
Heating systems in buildings — Calculation of load.
BS EN
14336
Installation & commissioning of water based heating sys
tems.
BS 6798 Installation of gas fired hot water boilers.
BS 5440
Part 1
Flues.
BS 5440
Part 2
Ventilation.
BS 7074 Expansion vessels and ancillary equipment for sealed wa
ter systems.
BS 7593 Treatment of water in domestic hot water central heating
systems.
BS 4814 Specification for Expansion Vessels using an internal dia
phragm, for sealed hot water systems.
IGE/UP/
7/1998
Guide for gas installations in timber framed housing.
3 Technical specifications
12 7696317 - 1 - 21032018

Tab.4 In IE the following Code of Practice apply:
Standard Scope
IS 813 Domestic Gas Installations.
The following standards give valuable additional information:
BS 5546 Installation of hot water supplies for domestic purposes.
BS EN
12828
Heating systems in buildings.
BS EN
12831
Heating systems in buildings — Calculation of load.
BS EN
14336
Installation & commissioning of water based heating sys
tems.
BS 7074 Expansion vessels and ancillary equipment for sealed wa
ter systems.
BS 7593 Treatment of water in domestic hot water central heating
systems.
3.2 Technical data
3.2.1 Technical information
Important
All data in these sections are nominal and subject to normal
production tolerances.
Important
LPG information can be found in Technical information - LPG,
page 75
Tab.5 General
Baxi Combi 224 228 424 428
Gas Council Numbers 47–077–21 47–077–22 47–077–23 47–077–24
Nominal heat input Domes
tic Hot Water — Maximum
Rate
Nett (Qn
Hi)
kW 24.7 28.9 24.7 28.9
Gross
(Qn Hs)
kW 27.4 32.1 27.4 32.1
Nominal Heat Input Central
Heating — Maximum Rate
Nett (Qn
Hi)
kW 20.6 24.7 20.6 24.7
Gross
(Qn Hs)
kW 22.9 27.4 22.9 27.4
Nominal Heat Input — Min
imum Rate
Nett (Qn
Hi)
kW 4.9 4.9 4.9 4.9
Gross
(Qn Hs)
kW 5.4 5.4 5.4 5.4
Nominal heat output
80/60°C — Domestic Hot
Water — Maximum Rate
Pn kW 24.0 28.0 24.0 28.0
Nominal heat output
80/60°C — Central Heating
— Maximum Rate
Pn kW 20.0 24.0 20.0 24.0
Nominal heat output
80/60°C — Central Heating
— Factory Setting
Pn kW 20.0 20.0 20.0 20.0
Nominal heat output
80/60°C — Minimum Rate
Pn kW 4.8 4.8 4.8 4.8
3 Technical specifications
7696317 - 1 - 21032018 13

Baxi Combi 224 228 424 428
Nominal heat output
50/30°C — Central Heating
— Maximum Rate
Pnc kW 21.8 26.1 21.8 26.1
Nominal heat output
50/30°C — Central Heating
— Minimum Rate
Pnc kW 5.2 5.2 5.2 5.2
Tab.6 Central heating circuit specifications
Baxi Combi 224 228 424 428
Maximum pressure bar 3 3 3 3
Minimum pressure bar 0.5 0.5 0.5 0.5
Central heating temperature adjust
ment ±5°C
°C 25/80 25/80 25/80 25/80
Expansion vessel water capacity litres 7.0 7.0 7.0 7.0
Expansion vessel pre charge pres
sure
bar 1.0 1.0 1.0 1.0
Maximum capacity of central heat
ing system
litres 120 120 120 120
Primary water content of boiler (un
pressurised)
litres 2.5 2.5 2.5 2.5
Tab.7 Domestic hot water circuit specifications
Baxi Combi 224 228 424 428
Maximum pressure bar 8.0 8.0 8.0 8.0
Dynamic minimum pressure bar 0.5 0.5 0.5 0.5
Minimum working water flow rate l/min 2.0 2.0 2.0 2.0
Specific flow rate (D) l/min 11.5 13.4 11.5 13.4
Domestic hot water temperature
range adjustment ±5°C
°C 35/60 35/60 35/60 35/60
Production of domestic water with
ΔT = 30°C
l/min 11.4 13.3 11.4 13.3
Production of domestic water with
ΔT = 35°C
l/min 9.8 11.5 9.8 11.5
Where low flow taps or fittings are intended to be used in the DHW system connected to the boiler, it is strongly recommended
that the DHW flow rate DOES NOT fall below 2.5 l/min. This will ensure reliable operation of the DHW function.
Tab.8 Characteristics of combustion
Baxi Combi 224 228 424 428
Natural gas rate (G20) Qmax m3/h 2.61 3.06 2.61 3.06
Natural gas rate (G20) Qmin m3/h 0.52 0.52 0.52 0.52
Diameter of coaxial discharge
pipes
mm 60/100 & 80/125 60/100 & 80/125 60/100 & 80/125 60/100 & 80/125
Important
Dynamic (nominal) inlet pressure (Natural gas — G20) 20mbar
with a CV of 37.78 MJ/m3
Tab.9 Electrical specifications
Baxi Combi 224 228 424 428
Nominal electrical power supply
voltage
V 230 230 230 230
Nominal electrical power supply
frequency
Hz 50 50 50 50
3 Technical specifications
14 7696317 - 1 - 21032018

Baxi Combi 224 228 424 428
Nominal power consumption when
firing
W 84 94 84 94
External fuse rating Amp 3 3 3 3
F2 Internal fuse rating — Connec
tion board ’B’
Amp 0.5 0.5 0.5 0.5
F1 Internal fuse rating — Main PCB
board ‘A’
Amp 1.6 1.6 1.6 1.6
Important
Boiler must be connected to an earth supply.
Tab.10 Other specifications
Baxi Combi 224 228 424 428
Degree of protection against hu
midity (EN 60529) without plug-in
timer / receiver fitted
IP IPX5D IPX5D IPX5D IPX5D
Degree of protection against hu
midity (EN 60529) with plug-in tim
er / receiver fitted
IP IPXO IPXO IPXO IPXO
Dimensions (height/width/depth) mm 700/395/279 700/395/279 700/395/279 700/395/279
Tab.11 Connections (copper tails)
Baxi Combi 224 228 424 428
Gas inlet mm 22 22 22 22
Heating flow mm 22 22 22 22
Heating return mm 22 22 22 22
Cold water inlet mm 15 15 15 15
Hot water outlet mm 15 15 15 15
Pressure relief discharge mm 15 15 15 15
Condensate discharge drain plastic
waste pipe
mm 21.5 21.5 21.5 21.5
Tab.12 Clearances
Baxi Combi 224 228 424 428
Above casing mm 183 183 183 183
Below casing (min)
Below casing (recommended)
mm
mm
200
250
200
250
200
250
200
250
Front — for servicing (min)
Front — for servicing (recommen
ded)
mm
mm
450
1000
450
1000
450
1000
450
1000
Front — for operation mm 6 6 6 6
Sides LH mm 5 5 5 5
Sides RH mm 5 5 5 5
Tab.13 Weights
Baxi Combi 224 228 424 428
Packaged boiler kg 30.0 30.0 30.5 30.5
Boiler lift weight (dry) kg 26.0 26.0 26.0 26.0
Installed weight (dry) kg 28.0 28.0 28.5 28.5
Installed weight when filled with wa
ter
kg 30.5 30.5 31.0 31.0
3 Technical specifications
7696317 - 1 - 21032018 15

3.2.2 Technical parameters
Tab.14 Technical parameters for boiler combination heaters
Baxi Combi 224 228 424 428
Condensing boiler Yes Yes Yes Yes
Low-temperature boiler(1) No No No No
B1 boiler No No No No
Cogeneration space heater No No No No
Combination heater Yes Yes Yes Yes
Rated heat output
Prated kW 20 24 20 24
Useful heat output at rated heat output
and high temperature regime(2)
P4 kW 20.0 24.0 20.0 24.0
Useful heat output at 30% of rated heat
output and low temperature regime
P1 kW 6.7 8.0 6.7 8.0
Seasonal space heating energy efficiency ƞs % 93 93 93 93
Useful efficiency at rated heat output and
high temperature regime
ƞ4 % 88.1 88.0 88.1 88.0
Useful efficiency at 30% of rated heat
output and low temperature regime
ƞ1 % 97.8 97.8 97.8 97.8
Auxiliary electricity consumption
Full load elmax kW 0.028 0.038 0.028 0.038
Part load elmin kW 0.011 0.011 0.011 0.011
Standby mode
PSB kW 0.003 0.003 0.003 0.003
Other items
Standby heat loss
Pstby kW 0.069 0.069 0.069 0.069
Ignition burner power consumption
Pign kW 0.000 0.000 0.000 0.000
Annual energy consumption
QHE GJ 62 74 62 74
Sound power level, indoors
LWA dB 48 50 48 50
Emissions of nitrogen oxides NOXmg/kWh 38 40 38 40
Domestic hot water parameters
Declared load profile XL XL XL XL
Daily electricity consumption
Qelec kWh 0.151 0.151 0.151 0.151
Annual electricity consumption
AEC kWh 33 33 33 33
Water heating energy efficiency ƞwh % 86 85 86 85
Daily fuel consumption
Qfuel kWh 22.770 22.930 22.770 22.939
Annual fuel consumption
AFC GJ 17 17 17 17
(1) Low temperature means for condensing boilers 30°C, for low temperature boilers 37°C and for other heaters 50°C return temperature
(at heater inlet).
(2) High temperature regime means 60°C return temperature at heater inlet and 80°C feed temperature at heater outlet.
See
The back cover for contact details.
3 Technical specifications
16 7696317 - 1 - 21032018

3.3 Dimensions and connections/clearances
Fig.3 Dimensions and connections
1
2
3
4
5 6 7
8
700
279
395
PN-0000501
1Safety valve
2Heating circuit water flow
3Condensate discharge
4Heating system/boiler drain tap
5Domestic hot water outlet
6Gas inlet
7Mains cold water inlet
8Heating circuit water return
A* Clearances below — 200mm minimum, 250mm recommended
B* Clearances in front — 450mm minimum, 1000mm recommended
The clearances shown in the diagram are minimum requirements to allow
for case removal, spanner access and air movement. These should be
observed at all times and kept clear of obstructions.
Fig.4 Clearances
A*
5.0
6
B*
285
700
395
PN-0000503
5.0
183
3 Technical specifications
7696317 - 1 - 21032018 17

Fig.5 Paper template
Ø 8
34 33.5 65 65 65 65 67.5
198 198
50 MIN
82.5
32
116 Dia Minimum
Aperture For
Flue Tube
Vertical Flue
Centre Line
Ø 22
Heating
Return
(22mm)
Heating
Flow
(22mm)
Hot Water
Outlet
(15mm)
Combi Only
Not System
Cold Water
Inlet
(15mm)
Combi Only
Not System
Side Clearance 5Side Clearance 5
Clearance below 250
Clearance above 183
Wall
View from under boiler
PN-0000504
3 Technical specifications
18 7696317 - 1 - 21032018

3.4 Electrical diagram
Fig.6 Electrical diagram
HMI
1
1
1
GND
1
1
PWM - P
L-BUS
E
1
1
1
L
N
G/Y
G/Y
W
Br
Bl
DV
PN-0000505
Bl
Br
Bl Br P
230V - 50Hz
Gy
R
W
Bk
Vt
Br
Bl 13
R
R
R
R
Gn
W
Br
R Bl Gn
Br
Bl
Y
Bk
Bk
R
R
Vt
Vt
Vt Vt
Br
Br
Br Br
R R Bk Bk
W
Br
1 2 3 4 5 1 2 3 4 5 6 7 1
2 1
1 2 3
Br
Br
Bl
Bk
Bk
Gy
Bl
W
Gy
Vt
Br
Bk
W
Gn
Br
R
Bl
R
L-BUS
Bk
R
W
Gn
Gn
Wk
Bk
Br
R
16
F1
F1 (1,6A)
L
N
L(CH)
L(DW)
N
GV
W8-1
W8-2 W8-4
W8-3
ST
HS
WPS
DS RS
FS
X6-A
X9-1
X14-A
X4-A W8
X5-A
X1-A
X3-A
X2-A
A
JP1
G/Y
G/Y
SERVICE
X7 X6 F2
0.5A
X14
OS
X13
J
X9
L-BUS
3
On
B
X12 X11 X10 X3
TIMER
X2
X5
Off
230V - 50Hz
LN
21
X1 MAINS
X4
RT
X8
OT
Gn
Bk
W4
W3
+
C2
C1
SIG
W2
W1
W5
F
1
2
1Circuit board ‘A’
2Circuit board ‘B’
Tab.15 Circuit board wiring
Br Brown Gy Grey Gn Green
Bl Blue R Red W White
G/Y Green/Yellow Vt Violet Mains (230V)
Bk Black
3 Technical specifications
7696317 - 1 - 21032018 19

Tab.16 Electrical connections inside the boiler (A)
X1–A
Electrical power supply 230 V — 50 Hz
1: Earthing connector
2: L (230 V)
3: N
X2–A
Pump
1: Earth connection
2: L (230 V)
3: N
X3–A
3-way valve
1: L (CH) 230 V — Heating circuit opening command
2: L (DW) 230 V — Domestic water circuit opening command
3: N — Common
X4–A Pump PWM signal
X5–A
Sensor connection
HS: domestic water request
RS: heating circuit water return
DS: heating circuit water flow
FS: flue gas
WPS: hydraulic pressure switch
ST: safety thermostat
X6–A Boiler PCB and control panel connection (electrical connection board)
X13–A Not used
X14–A Connection L-BUS
Tab.17 Electrical connections to be made to the boiler (B)
X1–B
Electrical power supply 230 V — 50 Hz
1: Earthing connector
2: L (230 V)
3: N
X4–B Room thermostat/timer (230V)
X6–B Not used
X7–B Solar probe connection
X8–B On-Off/R-Bus - Room thermostat connection (the jumper must be REMOVED to connect a device)
X9–B Service connection (SERVICE)
X13–B Connection L-BUS
X14–B Outside sensor connection (OS)
J
Dip-Switch
1: Maximum heating temperature OFF = 80°C - ON = 45°C (floor system)
2: OFF = Maximum output (heating) - ON = Boiler output 50% (heating)
3: DO NOT ADJUST
3 Technical specifications
20 7696317 - 1 - 21032018