ProLine® XE Ultra-Low NOx Outdoor Natural Gas Tankless Water Heater with X3® Technology

Model ATO-340HX3-N
4 out of 5 Customer Rating
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Installation Type
Fuel Source
Maximum BTU's

  • Maintains like-new performance for the life of the product vs. tankless models without X3 that show 10% efficiency reduction in the first 1.5 years
  • 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
  • Product Details
    • Maintains like-new performance for the life of the product vs. tankless models without X3 that show 10% efficiency reduction in the first 1.5 years
    • 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)
    • Recirculation pump capable with the use of a cross-over valve. Sold separately.
    • Ideal choice for residential single-family applications with continuous hot water needs and hard water concerns
    • Safety features include exhaust & water temperature safety control, overheat cut-off fuse and air-fuel ratio (AFR) sensor
    • Industry leading “Peace of Mind” 15-year limited warranty covers scale-related failures
    • Wall-mount design saves valuable space and allows for additional storage and flexibility

    • The ProLine® XE Condensing Ultra-Low NOx Outdoor Tankless Water Heater with X3® Scale Prevention Technology delivers continuous hot water, while protecting against scale build-up. Scale is the #1 enemy for tankless technology. With normal use, typical gas tankless water heaters begin to scale up over time. Scale reduces efficiency and increases annual cost of operation. Regular descaling is required to keep typical gas tankless water heaters operational, leading to ongoing maintenance costs. An expert in both water heating and treatment, A. O. Smith has combined the two technologies to achieve unparalleled protection on our condensing gas tankless water heaters with X3® Scale Prevention Technology. The technology prevents scale buildup, meaning virtually zero lifetime descaling maintenance and up to $2,800 in maintenance cost savings over the life of the product. X3® Scale Prevention Technology provides protection for the heat exchanger—making it last three times longer than a standard tankless water heater and maintaining like-new performance. A. O. Smith stands behind this revolutionary product with the industry’s first ever “Peace of Mind” limited warranty. Unlike competitive warranties, this 15-year limited warranty covers scale-related failures should they occur. The ATO-340HX3-N tankless water heater uses up to 180,000 BTU/hr of natural gas to deliver a continuous 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). This tankless water heater is extremely efficient with a Uniform Energy Factor of 0.93, and complies with Ultra-Low NOx regulations. These tankless water heaters utilize commercial grade copper alloy for the heat exchanger tubing and are approved to work with an external recirculation pump and cross-over valve. Certified up to 10,100 ft. altitude. A. O. Smith’s ProLine® water heaters are residential products built to commercial-grade standard and are only available for purchase through professional wholesalers and contractors.

    Specifications
    Tech Specs
    UEF
    0.94
    Maximum BTUs
    180,000
    Power Source
    GAS
    Limited Parts Warranty
    5 Years
    Water Connection Location
    BOTTOM
    Emissions
    Low NOx
    ASME Certified
    No
    Destination Country
    US
    Digital Display
    true
    Fuel Source
    NATURAL
    Installation Type
    OUTDOOR
    Limited Heat Exchanger Warranty 
    15 Years
    Max Flow Rate
    5.30
    Minimum BTUs
    15,000.00
    Application
    RESIDENTIAL
    Product Tier
    X3 Tankless
    Shipping Height 
    36.75
    Shipping Length 
    21.69
    Shipping Width 
    16.19
    Side Loop
    No
    Voltage
    120
    Dimension & Venting
    Type
    Water Heater
    Shipping Weight
    70.9lbs
    Vent Type
    Power Direct Vent
    Maintenance & Troubleshooting
    Maintenance

    Condensing Tankless with X3® Technology - Cartridge Installation

    Troubleshooting

    Condensing Tankless with X3® Technology - 111 Ignition Failure

    Condensing Tankless with X3® Technology - 121 Loss of Flame

    Condensing Tankless with X3® Technology - 991 Imperfect Combustion

    Marketing Videos
    Condensing Tankless with X3 Technology - How It Works
    Condensing Tankless with X3® Technology - Application and Installation
    Condensing Tankless with X3® Technology - Features and Benefits
    Take advantage of market incentives with ENERGY STAR® A.O. Smith water heaters
    All Reviews for ProLine® XE Tankless Condensing X3 (100 series)
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