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199,000 BTU ATI-540H Condensing Ultra-Low NOx Indoor Tankless Water Heater (NG)
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ATI-540H-N has been discontinued
Discontinued May 12, 2026
This product was discontinued by the manufacturer.
MANUALS (3)
Direct Replacement:
199,000 BTU ATM-199M Adapt SC Standard Condensing Ultra-Low NOx Tankless Water Heater (NG)
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VIEW REPLACEMENT
Product Highlights
–
Natural Gas
10 MAX GPM
Indoor Only
Direct Vent
120v
23.625" Height
Description
–
This unit is NOT approved for installation in Manufacture Homes and is not suitable for space heating applications only.
Product Details:
- Continuous flow rate up to 10.0 GPM
- Primary commercial-grade copper heat exchanger is 25x better than stainless steel at heat transfer, stabilizing outgoing water temperatures quicker
- Secondary heat exchanger is made of 316L Stainless Steel to protect against corrosion
- Highly efficient condensing Ultra-Low Nox tankless water heater delivers up to .94 Uniform Energy Factor (UEF)
- Flexible power direct vent design allows for venting up to 100 feet using either PVC, CPVC, polypropylene or ABS Pipe (solid core)
- Common vent up to 8 units
- Includes integrated temperature controls and advanced diagnostics to simplify troubleshooting
- Safety features include exhaust & water temperature safety control, overheat cut-off fuse and air-fuel ratio (AFR) sensor
- 15-year limited warranty on heat exchanger in residential applications
- The 540 series is well suited for residential use. Utilizing commercial grade copper alloy for the heat exchanger tubing, the 540 series is also suitable for heavier-residential usages such as domestic recirculation systems. Remote control included as a standard feature on all Outdoor models. Indoor models are certified up to 10,100 ft. altitude. Provides a variety of installation options: outdoor and direct vent. Complies with Ultra-Low NOx regulations and meets the energy efficiency requirements. Easy-Link System capable up to 4 units. The ATI-540H-N tankless water heater uses up to 199,000 BTU/hr of natural gas to deliver an endless supply of hot water for a 3 bath home in northern climates and up to a 4 bath home in southern climates (one shower head per bath). Utilizing condensing technology, this heater is extremely efficient with a Uniform Energy Factor of 0.93. With an industry leading 15-year limited warranty, the ATI-540H-N tankless water heater provides years of hot water through innovation and quality. A. O. Smith's ProLine water heaters are residential products built to commercial-grade standards and are only available for purchase through professional wholesalers and contractors.
Specs
–
| Product Type: | Tankless Heater |
|---|---|
| Installation Type: | Indoor Only |
| Type: | Condensing |
| Fuel Type: | Natural Gas |
| BTU (Max): | 199000 |
| BTU (Min): | 15000 |
| Vent Type: | Direct Vent |
| Energy Factor: | 0.93 |
| Gas Connection: | 3/4" |
| Water Connection: | 3/4" |
| Voltage: | 120v |
| Application: | Residential |
| Max Flow (GPM): | 10 |
| Inlet Gas Pressure: | 4.0-10.5"W.C |
| Height (Inches): | 23.625" |
| Width (Inches): | 17-3/4" |
| Depth (Inches): | 11-1/4" |
| Weight (lbs): | 59 lbs |
| Flow Rate at 40F Temp Rise (GPM): | 9.5 |
| Flow Rate at 70F Temp Rise (GPM): | 5.4 |
| Flow Rate at 60F Temp Rise (GPM): | 6.3 |
| Flow Rate at 50F Temp Rise (GPM): | 7.5 |
Questions?
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Call or text 888-757-4774
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Saturday – Sunday
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Product Reviews
4.5 out of 12 reviews
91% would recommend this product
5 star
75%
4 star
17%
3 star
0%
2 star
0%
1 star
8%
Most Liked Positive Review
Maybe the finest product I have bought in sometime
Recently installed a walk-in tub from American standard. Takes about sixty gallons of hot water to get the full relaxing experience with hot water. Immediately found that a sixty gallon storage hot water heater would not supply enough hot water, much less service other appliance needs such as laundry at the same time. The tankless units made by AOSmith supplied the bath with a continuous supply and everything else in the home ,too. Factory setting at 120 degrees was perfect. I cannot say enough about the ease of installation/ operation . Unit is the highest quality throughout. I went all out and bought the 199,000 BTU heater.
VS
Most Liked Negative Review
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Be careful
I ordered the same water heater product number on my old water heater. I didnt notice that I ordered a propane unit. Be careful when you order. The numbers are the same. Supply House would not refund my money.
Showing 1-10 of 12 reviews
Be careful
I ordered the same water heater product number on my old water heater. I didnt notice that I ordered a propane unit. Be careful when you order. The numbers are the same. Supply House would not refund my money.
Broke
Illinois
6 months ago
Verified Buyer
Was this review helpful to you?
Fast shipping and works perfectly
Our hot water heater went out and this was the same as the one we had for 9 years. Installed by plumbers in an hour and everything is good to go! Would definitely purchase something from this company again!
Erin
Goldsby Oklahoma
1 years ago
Verified Buyer
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Works as it should
Fast shipping, great price, quality is nice
Jimi716
Buffalo NY
1 years ago
Verified Buyer
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Yes
Very good machine
Babe
Nj
1 years ago
Verified Buyer
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Direct replacement for the same model from 13 years ago!
Easy drop in replacement for the same model that failed on me after 13 years. Plumbers wanted to replace it with inferior products for over $9,000. Thanks to SupplyHouse swapped it out myself for the cost of the unit and got better quality
Don't Need No Plumber (Bob)
Kansas City, MO
2 years ago
Verified Buyer
Was this review helpful to you?
I like it
Like it
Aron
Nyc
3 years ago
Verified Buyer
Was this review helpful to you?
Maybe the finest product I have bought in sometime
Recently installed a walk-in tub from American standard. Takes about sixty gallons of hot water to get the full relaxing experience with hot water. Immediately found that a sixty gallon storage hot water heater would not supply enough hot water, much less service other appliance needs such as laundry at the same time. The tankless units made by AOSmith supplied the bath with a continuous supply and everything else in the home ,too. Factory setting at 120 degrees was perfect. I cannot say enough about the ease of installation/ operation . Unit is the highest quality throughout. I went all out and bought the 199,000 BTU heater.
CRS
Alpharetta, Georgia
3 years ago
Verified Buyer
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Will buy for another house
Good product for this money. Work perfect.
Vic
Brooklyn
3 years ago
Verified Buyer
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Tankless water heater easy installation.
Used for a 2 bath home at 7000" seems to do okay water temp in a bit on the cooler side. Overall simple install.
Tiatnium
Salida, CO
5 years ago
Verified Buyer
Was this review helpful to you?
I like dealing with SupplyHouse.com
SupplyHouse.com has great products, Like AO Smith Tankless water heater, Great unit that produces hot water in very short time to the bathrooms at the end of the house. For us this a Win-Win from our old tankless. Service from SupplyHouse.com was Great, another Win-Win.
Bobear
Chino, California
5 years ago
Verified Buyer
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Product Q&A
1 Question1 Question
Q: what is the minimum flow rate to activate?
Asked by bobdabuilder 3 years ago
Add your answer
Verified Reply- SupplyHouseHi Bob! The minimum flow rate for activation is 0.5 GPM. After initial ignition, 0.4 GPM is required for continuous fire.
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