A.O. Smith GDHE-50 User Manual

A.O. Smith GDHE-50

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Instruction Manual

PRINTED 0413 322286-002

KEEP THIS MANUAL IN THE POCKET ON HEATER FOR FUTURE REFERENCE

WHENEVER MAINTENANCE ADJUSTMENT OR SERVICE IS REQUIRED.

POWER VENT/POWER DIRECT VENT GAS MODELS

WITH HOT SURFACE IGNITION

MODEL GDHE 50 SERIES 124/125

Complies with SCAQMD Low NOx Rule 1146.2

ALL TECHNICAL AND WARRANTY QUESTIONS: SHOULD BE DIRECTED TO THE LOCAL DEALER FROM WHOM THE WATER HEATER WAS

PURCHASED. IF YOU ARE UNSUCCESSFUL, CALL THE TECHNICAL SUPPORT PHONE NUMBER SHOWN ON THE WATER HEATER LABELING.

RESIDENTIAL GAS WATER HEATERS

• For Your Safety •

AN ODORANT IS ADDED TO THE GAS USED

BY THIS WATER HEATER.

Ashland City, TN 37015

www.hotwater.com

Thank you for buying this energy efcient water heater.

We appreciate your condence in our products.

Table of Contents

Other manuals for A.O. Smith GDHE-50

Replacement Parts List4 pages

Questions and Answers:

M
Marilyn CaseyJul 30, 2025
What to do if A.O. Smith Water Heater has no hot water?
- M
  Mrs. Tanya RivasJul 31, 2025
  First, check the breaker, fuses, and the water heater's on/off switch to ensure the A.O. Smith Water Heater is receiving power. Then, make sure the hot water supply valves to your fixtures are open. If the issue persists, the operating set point may be too low, or the differential setting too high, so try adjusting these. Also, check and adjust the Temperature Probe Offset setting. Colder incoming water temperatures may also lengthen the time required to heat water to desired temperature, so allow additional time for heating. Check for any hot water piping leaks or open faucets. Finally, sediment or lime scale accumulation may be affecting water heater operation, so cleaning the sediment or lime scale accumulation may help.
J
Joseph WalkerAug 6, 2025
How to adjust A.O. Smith Water Heater when water is too hot?
- R
  richardjohnsonAug 6, 2025
  If the water from your A.O. Smith Water Heater is too hot, the operating set point might be set too high; in this case, lower the operating set point. Alternatively, the Temperature Probe Offset settings may be improperly set, so check and adjust these settings.
M
Michael WagnerAug 14, 2025
Why A.O. Smith GDHE-50 is starting and operating roughly?
- K
  kendra52Aug 14, 2025
  Rough starting or operation of your A.O. Smith Water Heater can stem from several gas-related issues. It could be due to an undersized supply gas line causing low gas volume, low gas pressure, excessive supply gas pressure, or excessive manifold gas pressure. Using the incorrect fuel type can also cause this problem. Furthermore, vent gas recirculation at the vent and intake air pipe terminations on Direct Vent installations, excessive lengths of intake air and/or vent piping, clogged wire screens, or a clogged main burner might be the cause. Because of the complexity of the issue, it is best to contact a qualified installer or service agency for installation and service.
A
Alexander OlsonAug 21, 2025
What to do if A.O. Smith Water Heater is making noise?
- R
  Ruben HooverAug 21, 2025
  The noisy operation of your A.O. Smith Water Heater might be normal. The noise could be the normal operating sound of electrical components such as the combustion blower, transformer hum, or relay contact closure. No action is required in these cases, as it is normal operation.

A.O. Smith GDHE-50 Specifications

General

Brand	A.O. Smith
Model	GDHE-50
Category	Water Heater
Language	English

Summary

RESIDENTIAL GAS WATER HEATERS

What To Do If You Smell Gas

Essential steps to take when gas is detected, prioritizing safety and communication.

SAFE INSTALLATION, USE AND SERVICE

GENERAL SAFETY INFORMATION

Precautions and Grounding Instructions

Key safety precautions and mandatory grounding procedures for safe operation.

Hydrogen Gas Flammable Hazard

Information on the flammability of hydrogen gas and safety measures.

Burn Hazard from Hot Water

Warning about high water temperatures and the risk of severe burns.

INSTALLATION CONSIDERATIONS

LOCATING THE WATER HEATER

Flammable Vapors and Fire Hazard Warnings

Safety guidelines for preventing fire and explosion hazards in specific locations.

COMBUSTION AIR AND VENTILATION

INSTALLING THE NEW WATER HEATER

Power Supply and Electrical Considerations

Requirements for power supply, including polarity sensitivity and noise mitigation.

TEMPERATURE-PRESSURE RELIEF VALVE

Relief Valve Discharge Pipe Requirements

GAS PIPING

Sediment Traps and Gas Regulator

Installation of sediment traps and supply gas regulators for safe gas piping.

Condensate Piping

FILLING THE WATER HEATER

VENTING

Vent Pipe Termination and Planning

Guidelines for planning vent pipe routes and termination locations.

Vent Pipe Material and Lengths

MASSACHUSETTS INSTALLATION REQUIREMENTS

SIDEWALL POWER VENT TERMINATION CLEARANCES

SIDEWALL DIRECT VENT TERMINATION CLEARANCES

CONCENTRIC VENT INSTALLATION

DIRECT VENT DIAGRAMS

VENT PIPE PREPARATION

CONTROLS AND SWITCHES

Blower, Pressure, and Ignition Switches

Explanation of the function of various safety switches in the control system.

Power and Igniter Operation

OPERATING INSTRUCTIONS

Pre-Operation Safety Checks

Crucial safety checks and procedures to follow before lighting the water heater.

Starting and Turning Off the Heater

TEMPERATURE REGULATION

Scalding Hazards and Temperature Settings

Information on scalding risks and how to set safe water temperatures.

High Limit (ECO) Switch Function

CONTROL SYSTEM OPERATION

System Overview and Navigation

OPERATING STATES

USER SETTINGS & CONTROL SYSTEM MENUS

Temperature Settings Adjustment

HEATER STATUS AND INFORMATION

FAULT AND ALERT MESSAGES

Current Faults and History

Viewing current fault messages and reviewing fault history records.

Fault Occurrence and Default Reset

PERIODIC MAINTENANCE

Venting System and Anode Rod Inspection

Annual checks for venting system integrity and anode rod condition.

Temperature-Pressure Relief Valve Test

Procedure for testing the functionality of the T&P relief valve.

DRAINING AND FLUSHING

LEAKAGE CHECKPOINTS

TROUBLESHOOTING

Installation Checklist Review

A checklist to verify correct installation before troubleshooting.

Sequence of Operation Overview

SEQUENCE OF OPERATION FLOW CHART

OPERATIONAL PROBLEMS

Starting and Operation Issues

Common problems related to rough starting, momentary ignition, and general operation.

Water Temperature and Noise Issues

Fault and Alert Condition Identification

Identifying and understanding different fault and alert messages displayed.

FAULT AND ALERT MESSAGES (CONT.)

LIMITED RESIDENTIAL GAS WARRANTY

Warranty Conditions and Exceptions

Details on warranty coverage, limitations, and conditions for validity.

Service and Labor Responsibility

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