Tankless Water Heater Condensing Ultra-Low NOx Indoor 180,000 BTU Natural Gas

The 340H Series offers high efficiency Ultra-Low NOx condensing technology allowing for the use of 3” PVC venting and has 0” clearance to combustibles. Features copper primary and 316L stainless steel heat ex-changers to provide high efficiency operation and excellent corrosion resistance. Outdoor models include a remote controller as a standard feature. Indoor models are certified up to 10,100 ft. altitude. Provides a variety of installation options: indoor, outdoor and direct vent. Complies with Ultra-Low NOx regulations and meets the energy efficiency requirements of ASHRAE 90.1b-1992.

The ATI-340H-N tankless water heater uses up to 180,000 BTU/hr of natural gas to deliver an endless supply of hot water for a 2.5 bath home in northern climates and up to a 3.5 bath home in southern climates (one shower head per bath). Utilizing condensing technology, this heater is extremely efficient with a Uniform Energy Factor of 0.95. With an industry leading 15-year limited warranty, the ATI-340H-N tankless water heater provides years of hot water through innovation and quality.


  • Primary Heat Exchanger
  • The primary heat exchanger is constructed of commercial-grade copper, which is stronger than standard copper and more resilient against erosion.
  • 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.
  • Tech Specs
  • Emissions: Ultra-Low NOx
  • Maximum BTUs: 180,000
  • Minimum BTUs: 15,000
  • UEF: 0.95
  • Limited Heat Exchanger Warranty: 15 Years
  • Limited Parts Warranty: 5 Years
  • Water Connection Location: Bottom
  • Water Connection Size: 3/4"
  • Heat Exchanger: Commercial Grade Copper
  • Secondary Heat Exchanger: Stainless Steel
  • Voltage: 120
  • ENERGY STAR® Certified: Yes
  • LEED Rating: 1.5
  • 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: 58lbs/26kg
  • Shipping Weight: 69
  • Vent Type: Power Direct Vent
  • Vent Length: 70 feet at 3 diameter
  • 100 feet at 4 diameter
  • Vent Material: PVC, CPVC, PP, ABS, SS