Bosch AquaStar 125FX NG User Manual

WARNING: Improper installation,
adjustment, alteration, service or maintenance can
cause injury or property damage. Refer to this manual.
For assistance or additional information consult a
qualified installer, service agency or the gas supplier.
Upon completion of the installation, these instructions
should be handed to the user of the appliance for
future reference.
FEATURING: Automatic Variable Power Modulating Gas
Valve, Electronic Ignition and Power Venting
INSTALLATION AND OPERATING INSTRUCTIONS FOR AUTOMATIC
INSTANTANEOUS TYPE WATER HEATER FOR USE WITH NATURAL AND
LIQUEFIED PETROLEUM GAS
MODEL 125FX LP and 125FX NG
(Flow Modulated with Electronic Ignition and Power Venting  a Type III Category Appliance)
Suitable for heating potable water only
Not approved for space heating purposes
Intended for variable flow applications with steady cold water inlet temperatures.
For preheated domestic hot water, install the 125 BS model. For recirculating applications, install the 125 BL model.
WARNING
If the information in this manual is not followed
exactly. A fire or explosion may result causing property
damage, personal injury or death.
FOR YOUR SAFETY
Do not store or use gasoline or other flammable,
combustible or corrosive vapors and liquids in the
vicinity of this or any other appliance.
WHAT TO DO IF YOU SMELL GAS
- Close gas valve. Open windows.
- Do not try to light any appliance.
- Do not touch any electrical switch; do not use any
phone in your building.
- Immediately call your gas supplier from a neighbors
phone. Follow the gas suppliers instructions.
- If you cannot reach your gas supplier, call the fire
department.
- Installation and service must be performed by a
qualified installer, service agency or the gas supplier.
Specifications .................................................... Page 2
Rules for safe operation .................................... Page 4
Locating the Heater ............................................ Page 4
Combustion Air Requirements ............................ Page 5
Mounting the Heater ........................................... Page 6
Venting the Heater ............................................. Page 6
Gas Connections ............................................... Page 9
Water Connections .......................................... Page 10
Electrical Connections ......................................Page 11
Safety before turning on the heater ................... Page 12
Lighting and Operating instructions .................. Page 12
Setting water temperature ................................ Page 12
Maintenance & Service..................................... Page 13
Trouble Shooting .............................................. Page 14
Diagram of AquaStar......................................... Page 17
Components and Parts List .............................. Page 18
TABLE OF CONTENTS
6 720 606 455 (01.05) JS

Bosch AquaStar 125FX NG Specifications

General

Brand	Bosch
Model	AquaStar 125FX NG
Category	Water Heater
Language	English

Summary

For Your Safety

What to Do If You Smell Gas

Safety instructions for detecting and responding to gas leaks.

Principle of Operation

Specifications

Technical details and performance characteristics of the AquaStar 125FX.

Features

Lists the key features and benefits of the water heater.

Unpacking the Aquastar Heater

Guidance on unboxing the water heater and its components.

Minimum Installation Clearances

General Rules for Safe Operation

Proper Location for Heater

Combustion Air Requirements

Mounting Installation

Venting

Freeze Warning

Precautions against freezing in cold weather conditions.

Spill Switch Safety

Information about the spill switch safety feature.

Gas Piping and Connections

Gas Line Sizing

Tables and guidelines for selecting appropriate gas pipe sizes.

Maximum Inlet Pressure Settings

Water Connections

Pressure Relief Valve (PRV)

Guidance on connecting the pressure relief valve.

Electrical Connections

Operating Instructions

Safety Before Operating

Crucial safety checks and warnings before turning on the heater.

Lighting and Operating Instructions

Turn Off Gas To Appliance

Procedure for safely shutting down the gas supply to the heater.

Setting the Water Temperature

Maintenance and Service

Vent System Maintenance

Checking and cleaning the vent system annually.

Water Valve Service

Guidelines for periodic servicing of the water valve.

Pilot Flame Adjustment

How to inspect, clean, or replace the pilot burner assembly.

Trouble Shooting

Introduction to Troubleshooting

Overview of common water-related issues affecting performance.

No Spark at the Pilot

Steps to diagnose and fix the lack of a spark at the pilot.

Pilot Ignition Issues

Sparks but No Ignition

Troubleshooting when the pilot sparks but burners do not ignite.

Pilot Sparks Continuously

Diagnosing continuous sparking of the pilot without water flow.

Pilot Lights, Burners Off

Solutions when the pilot ignites but burners fail to come on.

Burner & Water Temperature Issues

Main Burners Go Out

Investigating why main burners shut off during hot water use.

Water Too Hot

Adjusting settings to reduce excessively hot water output.

Water Flow & Pressure Issues

Water Not Hot Enough

Diagnosing and fixing insufficient hot water temperature.

Temperature Fluctuations

Addressing inconsistent hot water temperatures.

Inlet Water Pressure Issues

Checking and resolving issues with inlet water pressure or tanks.