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Rheem RTG74 User Manual

Rheem RTG74
82 pages
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Tankless Gas Water Heaters
Second Generation
Indoor, Outdoor and Direct Vent
Up to 199,000 BTU
Includes RTG2-42, RTG53, RTG66 and RTG74 models
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Table of Contents

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Rheem RTG74 Specifications

General IconGeneral
TypeTankless
Maximum Flow Rate7.4 GPM
Energy Factor0.82
Activation Flow Rate0.4 GPM
Minimum Flow Rate0.4 GPM
Voltage120V
Fuel TypeNatural Gas
Temperature Range98°F - 140°F
Dimensions26 in. H x 18.5 in. W x 9.8 in. D
Warranty12 years

Summary

Sequence of Operations

Sensors and Safety

Oxygen Depletion Sensing System Operation

Explains the function of the ODS sensor in detecting and responding to low oxygen levels.

ODS Timer and Overheat Protection

How to Reset the Four (4) Hour ODS Timer

Step-by-step guide to reset the ODS timer using the control board dip switches.

Overheat Film Wrap Component

Describes the overheat film wrap's role in detecting high temperatures and its error code.

Thermistor and Display Information

Heat Exchanger Thermistor

Monitors heat exchanger water temperature and triggers error codes.

Maintenance Panel Display

Accesses diagnostic information via the remote control panel.

Fault History and Burner Adjustment

Clearing the Fault History

Procedure for clearing fault history from the unit's memory.

Adjusting the Burner Control Assembly (PCB)

Procedure to balance fuel pressure and air volume for optimal burner performance.

Manifold Gas Pressure Checks

How to Check Manifold Gas Pressure

Guide to measuring and verifying manifold gas pressure for proper operation.

Program Chip Adjustment

Maximum Temperature Setting Adjustments

Changing the Maximum Temperature Setting to 140°

Procedure to set the maximum water temperature to 140 degrees Fahrenheit.

Changing the Maximum Temperature Setting to 120°

Procedure to revert the maximum water temperature setting to 120 degrees Fahrenheit.

Error Codes Summary List

Printed Circuit Board Diagnostic Points

Thermistor Resistance Reference Chart

Fan Speed Reference Chart

RTG2-42 Model Information

Wiring Diagram

Electrical schematic for the RTG2-42 model, showing component connections.

Printed Circuit Board

Visual guide to the RTG2-42 printed circuit board components.

RTG 53 Model Information

Wiring Diagram – RTG 53

Electrical schematic for the RTG 53 model, detailing component connections.

Printed Circuit Board – RTG 53

Visual guide to the RTG 53 printed circuit board components.

RTG 66 Model Information

Wiring Diagram

Electrical schematic for the RTG 66 model, showing component connections.

Printed Circuit Board

Visual guide to the RTG 66 printed circuit board components.

Error Code 11 Troubleshooting (RTG66)

Error Code 51 Troubleshooting (RTG66)

Error Code 61 Troubleshooting (RTG66)

Error Code 65 Troubleshooting (RTG66)

Error Code 66 Troubleshooting (RTG66)

RTG 74 Model Information

Wiring Diagram – RTG 74

Electrical schematic for the RTG 74 model, showing component connections.

Printed Circuit Board – RTG 74

Visual guide to the RTG 74 printed circuit board components.

MIC-180 and EZ Link System Operation

MIC-180 Printed Circuit Board Identification

Visual identification of components on the MIC-180 printed circuit board.

Error Code 03 Troubleshooting (MIC-180/EZLink)

Test Run Mode Procedure

MIC 180 Maintenance Mode Table

Maintenance Information Mode Access

2nd Generation Flame Rod Chart Reference

General Troubleshooting Guide

Troubleshooting Format and Example

Explains the flowchart methodology used for troubleshooting.

Unit Will Not Power On Troubleshooting

Error Code 11 Troubleshooting (General)

Error Code 12 Troubleshooting

Error Code 13 Troubleshooting

Error Code 14 Troubleshooting

Error Code 15 Troubleshooting

Error Code 16 Troubleshooting

Error Code 21 Troubleshooting (Indoor Models)

Error Code 24 Troubleshooting

Error Code 29 Troubleshooting

Error Code 31 Troubleshooting

Error Code 32 Troubleshooting

Error Code 33 Troubleshooting

Error Code 34 Troubleshooting

Error Code 35 Troubleshooting

Error Code 38 Troubleshooting

Error Code 51 Troubleshooting

Error Code 52 Troubleshooting

Error Code 61 Troubleshooting

Error Code 65 Troubleshooting

Error Code 66 Troubleshooting (RTG66 Only)

Error Code 71 Troubleshooting

Error Code 72 Troubleshooting

Error Code 76 Troubleshooting

Error Code 79 Troubleshooting

Error Code 80/81 Troubleshooting

Error Code 82 Troubleshooting

Error Code 90 Troubleshooting

Error Code 99 Troubleshooting

Warning Code IL Procedure

Warning Code P1 Explanation

1st Generation 7.4 Series Disassembly and Repair

Printed Circuit Board (PCB) Replacement

Steps for safely removing and replacing the Printed Circuit Board.

Air Filter Switch Replacement

Water Inlet Solenoid, Connector, and Thermistor Replacement

Component Replacement Procedures (Page 72)

Hot Water Outlet Connector and Thermistor Replacement

Steps for removing the hot water outlet connector and thermistor.

Transformer Replacement

Steps for removing and replacing the transformer unit.

Fan Assembly Replacement

Proportional Gas Flow Regulator (Gas Valve) Replacement

Burner Plate Cover Replacement

Burner Assembly Replacement

Igniter and Igniter Probes Replacement

Flame Rods Replacement

Heat Exchanger Thermistor Replacement

Parts Exploded View: RTG2-42PV & RTG 53PV

Parts Exploded View: RTG 53X

Parts Exploded View: RTG 53DV

Parts Exploded View: RTG 66DV

Parts Exploded View: RTG 74PV & GT 199PV

Parts Exploded View: RTG 74DV & GT 199DV

Parts Exploded View: RTG 74X & GT 199X

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