Bosch Model GWH 425 - Manual (Page 2)

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2
Index
Index
1 Warning 2
2 Appliance details 3
2.1 GWH 425 PN specifications (Technical data) 3
2.2 Unpacking the GWH 425 PN heater 4
2.3 General rules to follow for safe operation 4
2.4 Dimensions and installation clearances 5
3 Installation instructions 6
3.1 Introduction 6
3.2 Proper location for installing your heater 6
3.3 Heater placement and clearances 6
3.4 Mounting Heater 7
3.5 Combustion air requirements 8
3.6 Venting 9
3.7 Gas piping & connections 11
3.8 Measuring gas pressure 13
3.9 Water connections 13
3.10 Recirculation application 14
4 Operation instructions 14
4.1 For your safety read before operating your water heater 14
4.2 Lighting instructions 15
4.3 To turn off appliance 15
4.4 Setting the water temperature 16
4.5 Draining water from heater 16
5 Maintenance and service 17
5.1 Maintenance intervals 17
5.2 Water valve 17
5.3 Pilot 17
5.4 Main burners 18
5.5 Vent assembly 18
5.6 Mineral scale build-up 18
6 Troubleshooting 19
6.1 Introduction 19
6.2 Pilot does not light 19
6.3 Pilot lights, but goes out when button is released 19
6.4 Pilot goes out during or after hot water use 19
6.5 Burners do not light with water flow 20
6.6 Hot water temperature fluctuates at tap 20
6.7 Water is too hot 21
6.8 Water is not hot enough 21
6.9 Burners ignite without hot water flow 21
6.10 Low hot water pressure 21
6.11 Noise when heater is running 21
6.12 Burners do not operate cleanly; yellow flames
when operating
22
7 Protecting the environment 23
8 Interior components and diagram parts list 24
8.1 Interior components 24
8.2 Components diagram 25
8.3 Parts list 26
9 Fifteen Year Limited Warranty 27
1 Warning
Fig. 1
Warning: The heater must be isolated
from the gas supply piping system
during any pressure testing of that
system at test pressures equal to or
more than 0.5 psig.
Caution: Any changes or
modifications not expressly approved
by the party responsible for compliance
could void the user’s authority to
operate the equipment.