Tankless Water Heater Condensing Ultra-Low NOx Indoor 199,000 BTU Natural Gas

Tankless Water Heater Condensing Ultra-Low NOx Indoor 199,000 BTU Natural Gas

Model ATI-540H-N

Tankless Water Heater Condensing Ultra-Low NOx Indoor 199,000 BTU ATI-540H-N is rated 4.9048 out of 5 by 21.
Rated 5 out of 5 by from Finally enough hot water I just bought this product, as so far it has been great, we can finally use our Jacuzzi tub and actually have hot water to fill it completely without ever getting cold. And still have hot water for the family to take care of their needs too.
Date published: 2015-03-21
Rated 5 out of 5 by from Even My Plumber Likes It ! I about to begin life with a tankless water heater. We've suffered through two (2) previous hot water tank leaks that flooded the downstairs. My plumber had never seen or installed the ATI 540H 100 before and he told me he was so impressed he planned to install one in his own house. He said it was a little heavier than what he had installed in the past, but he liked the two heat exchangers which allowed he unit to dissipate heat and have a cooler exhaust.
Date published: 2015-02-06
Rated 5 out of 5 by from Installed like a breeze - will save me $$$ Had to update the gas line to 3/4 for this heater. Great manual ! Awesome instruction on how to install. Piped it up - plugged it in and works like a champ. It is quiet like a mouse, but I don't care since its in the garage on the wall. Plan to put a recirculation pump on it in a few months with a timer for the AM shower at the other end of the house. Just need a few more valves and such for the new setup. People say this is an awesome money saver. I am happy to be part of the club !
Date published: 2015-01-31
Rated 5 out of 5 by from Great water heater I had a different brand it was not good I had it for a year and heat exchanger started leaking
Date published: 2015-01-24
Rated 5 out of 5 by from Great control features So glad that we don't run out of hot water! Love it!
Date published: 2015-01-02
Rated 5 out of 5 by from Nice Hot Shower I've had this tankless hot water heater for about 2 months and it works great. Now the only problem is I hate to get out of my nice hot shower!
Date published: 2014-12-30
Rated 5 out of 5 by from American made and efficient-Tankless Water Heater I purchased the A.O. Smith Tankless Water Heater and it was installed by Richard Witham Plumbing here in Collierville, TN. We are very pleased with the product, as it provides us with continuous hot water, and the unit is very "low-noise." Most of all, the product is American-made! We love it.
Date published: 2014-12-26
Rated 5 out of 5 by from IT'S A NO BRAINER I used a system like this in Europe many years. it was no where near as efficient as this unit. I can't believe how fast the hot water is at the tap. I take long showers and the temp. never waivered. these machines should be installed in every household. just think, you never have to keep a tank of water hot for when you need it. it's a great energy saver and environmental saver. (the only time you use gas is when you use the hot water.) AS FOR APPEARENCE it can hang in pretty much any utility closet. see install guide.
Date published: 2014-12-23
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The 540H is well suited for residential/commercial applications such as small restaurants and beauty salons. Utilizing HRS35 copper alloy for the heat exchanger tubing, the 540H is also suitable for heavier-residential usages such as space heating or domestic recirculation systems. Remote control included as a standard feature. Indoor models are certified up to 10,100 ft. altitude. Thicker heat exchanger drum and utilizes HRS35 (heat-resistant) copper for the heat exchanger tubing. Provides a variety of installation options: outdoor and direct vent. Includes a pump control port, ensuring efficient operation of all circulation pumps. Complies with Ultra-Low NOx regulations and meets the energy efficiency requirements of ASHRAE 90.1b-1992. Easy-Link System capable up to 4 units. Multi-Link System capable up to 20 units.

The ATI-540H-N tankless water heater uses up to 199,000 BTUs of natural gas to deliver a max flow rate of 6.6 GPM. It utilizes condensing technology to achieve an Energy Factor of 0.95, and is ENERGY STAR® qualified. This model meets Ultra-Low NOx emission requirements, and comes with a 15-year limited warranty.

Where to Buy

Where to Buy

Woodbridge, NJ 07095

Location #1

Jersey Pipeline Plumbing & Heating Inc.

Freehold, NJ

More Info >>
Location #2

Tuga Plumbing

Union, NJ

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Location #3

Authorized Heating

Brooklyn, NY

More Info >>
View All List My Company Here

Product Features & Options

Dual Heat Exchanger

The primary heat exchanger is constructed of commercial-grade HRS35 copper, which is stronger than standard copper and more resilient against erosion. Condensing models feature 316L stainless steel secondary heat exchanger, providing additional protection against corrosion.

Safety Features

Includes freeze, overheat, surge protection and troubleshooting diagnostic codes.

Space Savings

A. O. Smith tankless water heaters take up much less space that your conventional tank-style water heater. With no tank to steal valuable storage space, our wall-mount design allows for additional storage and flexibility.

Endless Hot Water

The comprehensive line of A. O. Smith tankless water heaters are an excellent whole-home water heating solution that supply endless hot water.

How it Works

The comprehensive line of A. O. Smith tankless water heaters provide hot water on-demand.

• A hot water tap is opened
• The opened tap allows water to flow through the water heater. An internal water flow sensor detects this flow
• Upon flow detection, the flow sensor sends the activation signal to the computer board
• The computer automatically ignites the burner
• As water flows through the heat exchanger, it absorbs heat from the burner
• By the time the water exits the heater, it has reached the designated set temperature
• When the hot water tap is closed, the water heater automatically turns off




limited warranty


energy factor

CSA International Low Lead Content Certification in compliance with U.S. and Canadian safety standards on gas components
AHRI Air-Conditioning, Heating and Refrigeration Institute
CSA International Design Certification The CSA Blue Star indicates the product is certified to applicable U.S. standards for appliances using gas or other petroleum fuel
CSA International Certification in compliance with U.S. and Canadian for gas appliances and other liquid petroleum, LP, propane products

Product Specifications

Tech Specs
Emissions: Ultra-Low NOx
Maximum BTUs: 199,000
Minimum BTUs: 15,000
Limited Heat Exchanger Warranty: 15 Years
Limited Parts Warranty: 5 Years
Water Connection Location: Bottom
Water Connection Size: 3/4"
Heat Exchanger: HRS35 Copper Alloy
Secondary Heat Exchanger: Stainless Steel
Voltage: 120
Energy Factor: 0.95
Digital Display: Yes
Remote Control: Yes
Technology: Condensing
Dimensions & Venting
Type: Space Saving
Height: 23 5/8"
Width: 17 3/4"
Depth: 11 1/4"
Product Weight: 59lbs/27kg
Shipping Weight: 63lbs
Vent Type: Direct Vent
Vent Length: 70 feet at 3 diameter
100 feet at 4 diameter
Vent Material: PVC, CPVC, PP, ABS, SS


Rebate and incentive programs provide cash-back to consumers for the purchase of appliances that meet certain energy efficiency standards. Often, these standards are tied to the ENERGY STAR® program.

Cash for Appliances is designed to encourage the purchase of energy efficient appliances. Consumers who purchase ENERGY STAR® or CEE qualified appliances can receive cash rebates. Most states are offering rebates in the $50 to $250 range.


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Need More Hot Water?

There's no reason to run out of hot water. If you're not sure that the ATI-540H-N provides enough hot water for your needs, consider these:

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Vertex™ 100 Power Direct Vent 50-Gallon Gas Water Heater

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Vertex™ Power Vent 50-Gallon Gas Water Heater

  • 6 Year Limited Warranty
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