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A.O. Smith ATI-540H-N - User Manual

A.O. Smith ATI-540H-N
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Gas Tankless Water Heater
TM
Suitable for potable water heating and space-heating
Please refer to local codes for space-heating compliance.
540 (T-H3)
model only
If you have any questions, please
call or write to:
500 Tennessee Waltz Parkway
Ashland City, TN 37015
Toll Free: 1-877-737-2840
WARNING
- Do not store or use gasoline or other
flammable vapors and liquids in the vicinity
of this or any other appliance.
- WHAT TO DO IF YOU SMELL GAS
• Donottrytolightanyappliance.
• Donottouchanyelectric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.
On-Demand Water Heater
Installation Manual and Owner’s Guide
ANSI Z21.10.3 and CSA 4.3
If the information in these
instructions is not followed
exactly, a fire or explosion may
result causing property damage,
personal injury or death.
FEATURING
• ENDLESSHOTWATER
• ON-DEMANDUSAGE
• COMPACT,SPACESAVING
• ENERGYCONSERVATION
• COMPUTERIZEDSAFETY
• NOPILOTLIGHT
• Satisfiesthe2012SCAQMDRule
1146.2 for Ultra-Low NOx
Emissions
• EASY-LINKSYSTEMAND
MULTI-UNIT SYSTEM
(540 (T-H3) model only)
Models
• 240Outdoor(T-H3J-OS)
• 340Outdoor(T-H3S-OS)
• 540Outdoor(T-H3-OS)
• 240Indoor(T-H3J-DV)
• 340Indoor(T-H3S-DV)
• 540Indoor(T-H3-DV)
Downloaded from http://GadgetsGo.com Authorized Dealer

Table of Contents

Questions and Answers

  • R
    robertsonjesseAug 8, 2025
    Why is there no hot water when I open a fixture with my A.O. Smith Water Heater?
    • B
      Brittany AcostaAug 8, 2025
      If hot water isn't available when you open a fixture with your A.O. Smith Water Heater, ensure the unit has a 120 VAC, 60 Hz power supply. If you're using a remote or temperature controller, check if it's powered on. Also, verify that both the gas and water supply valves are fully open. Check if the filter on the cold water inlet is clean and ensure the hot water fixture is open enough to draw at least 0.5 GPM through the heater. Finally, check that the unit isn't frozen and, for propane models, that there is enough gas in the tank or cylinder.
  • J
    Jennifer WaltersAug 13, 2025
    Why is my A.O. Smith ATI-540H-N water not hot enough?
    • C
      Christopher GeorgeAug 13, 2025
      If the water from your A.O. Smith Water Heater isn't hot enough, start by checking for cross plumbing between cold and hot water lines. Ensure the gas supply valve is fully open and that the gas line is properly sized. Also, confirm that the gas supply pressure is sufficient and that the set temperature isn't too low.
  • J
    Joseph AndradeAug 18, 2025
    Why is the hot water temperature fluctuating in my A.O. Smith ATI-540H-N Water Heater?
    • A
      Alejandra WhiteAug 18, 2025
      If you're experiencing temperature fluctuations with your A.O. Smith Water Heater, start by checking if the filter on the cold water inlet is clean. Verify that the gas line is properly sized and the supply gas pressure is sufficient. Also, check for cross connections between the cold and hot water lines.
  • J
    Joshua WilliamsAug 23, 2025
    What to do if A.O. Smith Water Heater water is too hot?
    • V
      vanessa84Aug 23, 2025
      If the water from your A.O. Smith Water Heater is too hot, check if the set temperature is set too high.
  • K
    Karen GardnerAug 27, 2025
    What to do if hot water turns cold and stays cold with A.O. Smith ATI-540H-N?
    • K
      Kari OdonnellAug 28, 2025
      If the hot water from your A.O. Smith Water Heater turns cold and stays cold, check if the flow rate is sufficient to keep the water heater running. If a recirculation system is installed, ensure the recirculation line has enough check valves. Also, verify the gas supply valve is fully open and the filter on the cold water inlet is clean. Make sure your fixtures are free of debris and obstructions and check if the flow rate is too low.
  • A
    Ashley NobleSep 1, 2025
    How to get hot water faster from my A.O. Smith Water Heater?
    • T
      Timothy MaxwellSep 2, 2025
      The time it takes to get hot water from your A.O. Smith Water Heater depends on the length of piping between the heater and the fixtures. The longer the distance or the bigger the pipes, the longer it will take. If you want hot water faster, consider a hot water recirculation system.

Summary

Product Specifications

Safety Guidelines

Safety Definitions

Explanation of safety alert symbols like DANGER, WARNING, and CAUTION.

General Safety Rules

Essential general safety instructions to follow before and during operation.

Installation

General Installation Guidelines

Follow local codes, ensure proper ventilation, and check unit compatibility.

Clearances

Required minimum clearances around the water heater for safe installation.

High-Altitude Installations

Instructions for setting DIP switches based on installation altitude.

Venting Instructions

Guidelines for proper venting, including material types and configurations.

Gas Supply and Pipe Sizing

Ensuring proper gas supply and sizing gas pipes for safe operation.

Water and Electrical Connections

Procedures for connecting water lines, pressure relief valves, and electrical power.

Operation

Initial Operation and Safety Checks

Steps for first-time startup, safety checks, and operating the water heater.

Normal Operation and Temperature Control

Operating the heater normally, using controllers, and setting temperatures.

Controller Features and Settings

Information, unit conversion, and PCB temperature settings for controllers.

Maintenance, Troubleshooting, and Parts

Flow Rate and Freeze Protection

Information on water flow rates and the unit's freeze protection system.

Maintenance and Filter Cleaning

Routine maintenance procedures, including draining and cleaning the filter.

Troubleshooting and Error Codes

Diagnosing common problems, interpreting error codes, and finding solutions.

Components Diagram and Parts List

Visual diagrams of components and a list of available replacement parts.

Warranty Information

A.O. Smith ATI-540H-N Specifications

General IconGeneral
BrandA.O. Smith
ModelATI-540H-N
TypeTankless Water Heater
Fuel TypeNatural Gas
Maximum Flow Rate10 GPM
Flow Rate10 GPM
Thermal Efficiency95%
Ignition TypeElectronic
Voltage120V
Heating Capacity199, 000 BTU
Maximum BTU Input199, 000 BTU/hr
VentingDirect Vent
Warranty15-Year Limited on Heat Exchanger, 5-Year Limited on Parts
Gas Connection3/4 inch
Water Connection3/4 inch NPT

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