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Index
Index
1 Warning 3
2 Appliance details 4
2.1 Features 4
2.2 GWH C 920 ES and GWH C 920 ESC
Specifications (Technical data) 5
2.3 Unpacking the tankless water heater 6
2.4 General rules to follow for safe operation 7
2.5 Dimensions and minimum installation
clearances 8
3 Installation instructions 9
3.1 Specialized tools 9
3.2 Introduction 9
3.3 Venting 9
3.4 Combustion air requirements 20
3.5 Proper location for installing your heater 21
3.6 Heater placement and clearances 21
3.7 Mounting installation 21
3.8 Gas piping & connections 22
3.9 Water connections 25
3.10 Water quality 26
3.11 Domestic hot water recirculation 27
3.12 Filling the condensate trap 28
3.13 Measuring gas pressure 29
4 Electrical connections 30
4.1 Electrical power supply 30
4.2 Position of the fuses in control unit 30
5 Operation instructions 31
5.1 Description of LCD Display 31
5.2 For your safety read before operating
your water heater 32
5.3 Power 32
5.4 Temperature selection 32
5.5 Use of optional remote control accessory
(part no. TSTAT2) 33
5.6 Operation 33
5.7 Reset button 33
5.8 Program button 33
5.9 Locked condition 34
6 Maintenance and service 34
6.1 Annual maintenance 34
6.2 Winterizing for seasonal use 35
6.3 Mineral scale build-up 35
6.4 Condensing heat exchanger unit 36
6.5 Adjusting CO2 36
6.6 Program values 39
6.7 Control unit diagnostics 40
7 Troubleshooting 41
7.1 Introduction 41
7.2 Burner does not ignite when hot water
is turned on 41
7.3 Water is too hot 41
7.4 Water is not hot enough 41
7.5 Low water flow/pressure 42
7.6 Hot water temperature fluctuates at tap 42
7.7 Noisy burner/heater during operation 42
8 Error codes 44
8.1 Error code diagnostics 44
9 Electrical diagram 48
10 Sensor resistance charts 49
11 Functional scheme 51
12 Interior components diagram
and parts list 52
12.1 Interior components 52
12.2 Components diagram 54
13 Protecting the environment 61
14 Limited Warranty 62
14.1 Limited warranty for GWH C 920 ES
residential model 62
14.2 Limited warranty for GWH C 920 ESC
commercial model 63
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