American Tankless Water Heaters: Features to Look For

American tankless water heaterAmerican tankless water heater

If you are looking to buy a product with on-demand water heating, American tankless water heaters made by an American heating company and owned by the AO Smith Corporation, might be a solution for you. See the review of the models and the main features below.

The main reasons for buying an American tankless are an endless and continuous supply of hot water, on-demand water heating at the pre-set temperature, small and compact size, and the Energy Star compliance with the high energy savings.

Below is a review of the most advanced features and benefits.


American tankless water heaters: What to look for


American tankless water heaters can be found in several categories, all designed for residential and light-duty commercial water heating. Tankless units come with different capacities, power ranges, and installation options. All of them are wall-mounted; some are direct vented units for indoor use, while others are for outdoor installation and do not require venting.

Tankless technology

The main advantages of the American tankless heaters over storage tank-type models are the continuous supply of hot water and technology that provides hot water on demand and when it is needed, for point-of-use service or the whole house use.

Energy Star compliance

The tankless models come with an energy efficiency of a minimum of 84% and have an excellent performance level, which helps in reducing energy loss and increasing money savings. They are Energy Star compliant, and thanks to the high energy factor, are eligible for rebates.

Controlled operation

Standard equipment like direct electronic ignition and accurate remote temperature control of +/-2 F are also helping reduce energy waste.

The temperature remote controller is a standard feature. It allows you to set the temperature, monitors the operation, and check if something is wrong with the heater, using a diagnostic system and displayed error codes.


Every American tankless water heater uses natural gas, which is a factory set option but can be easily converted to use propane gas. The efficient gas burner was designed to produce fewer NOx gases, making these water heaters environmentally friendly or "green."

Flexible venting

Indoor models are direct vented and combustion sealed, so the outside air is drawn inside the combustion chamber while the inside air is protected from being used.

At the same time, the flue gases, as products of combustion, are forced out through the venting system. The venting pipes, either short or long, can be directed either horizontally or vertically, which adds even more flexibility to the installation.


Every American tankless water heater built for residential use comes with a 15-year limited warranty on the heat exchanger and a 5-year warranty on parts. They are used not only for potable water heating but in hydronic heating, radiant floor heating, recirculation, and a combination of domestic and heating applications.

American tankless water heaters: Models and specifications

American 110, 310, 510 series

GT-110-NI and GT-110-NE are indoor and outdoor models used for residential and light commercial applications. A fully modulating gas blower is a standard feature for every American tankless water heater, and for 110 series, it allows the power range from 19,500 to the maximum of 140,000 BTU.

The heaters provide a maximum of 6.6 gallons per minute of hot water, which makes them recommended for 1-2-bath homes, apartments, condos, and cabins.

GT-310-NI is an indoor direct vent, and GT-310-NE is the outdoor model, both designed with the gas input from 11,000 to 190,000 BTU and a maximum water flow of 8.0 GPM, which is perfect for 2-3 bath homes.

GT-510-NI and GT-510-NE have a minimum gas input of 11,000 and a maximum of 199,000 BTU, and the water flow reaches a high 10 GPM. Without using the additional accessories, these models can be linked to up to 4 units for homes with higher demand. The 510 series can be used in residential and light commercial applications, in restaurants, high-demanding homes, and space heating.

American 320 and 520 series

GT-320-NIH and GT-302-NEH are high-efficiency and condensing tankless water heaters that use two heat exchangers for more efficient heating and energy savings. Like the previous models, they produce maximum hot water of 8.0 GPM but have slightly different gas inputs; 13,000 for the minimum and 80,000 BTU for the maximum, including a higher energy factor of 0.91.

They are equipped with an LCD display that shows the temperature and the error codes for easy troubleshooting.

GT-520-NIH and GT-520-NEH are condensing and tankless water heaters that are can provide high energy efficiency (EF is 0.91) and 9 GPM hot water flow rate in continuous supply. A convenient built-in display shows the temperature and error codes. Easy-Link allows up to 4 units to be connected and work as one.

305, 505 and 705 series

American tankless water heater from GT-305 series is designed to work with min 15,000 BTU/h and max. 180,000 BTU/h gas input, providing a maximum of 7.5 GPM of hot water.

Models GT-505 are designed to work within the range of min 15,000 BTU/h and max. 199,000/190,000 (propane) BTU/h gas input, providing a maximum of 9.4 GPM of hot water.

American tankless models GT-705 are designed to work with the min. 19,000 BTU/h and max. 237,000 BTU/h of gas input, providing a maximum of 9.8 GPM of hot water. The 705 models are not Energy Star considered as the rule applies only to units up to 199,000 BTU/h.

110U, 310U and 510U series

Water heaters from 110U, 310U, and 510U series are known as ultra-low NOx models.

American 240, 340 and 540

GT-240, GT-340, and GT-540 are condensing tankless models that are designed with the power vent system and the built-in temperature controller for advanced diagnostics and easy troubleshooting.

All models utilize two heat exchangers and a high energy factor of 0.95 for maximum efficiency and energy savings.

The best model is GT-540, as it provides a high water flow of 10 gallons per minute and can use Easy-Link and Multi-Link systems to provide even more hot water.


  • Heat exchanger
  • Heat exchanger thermistor or over-heat switch
  • Gas burner
  • Spark electrode and flame rod (it proves ignition)
  • Flue outlet
  • Combustion fan - when it is energized, it purges the combustion chamber
  • Solenoid valves
  • Thermal fuse
  • PC board - monitors inlet and outlet water temperature inside the tankless water heater, flow rate, flame rod, fan motor frequency...
  • Frost sensing switch
  • Modulating gas control valve - modulates gas input to the required value
  • Water flow device and sensor - send pulses to PCB when minimum water flow is established
  • Water inlet and outlet

Safety features

  • The overheating system shuts the tankless water heater automatically if the temperature rises much higher than the pre-set temperature.
  • If the above overheating system fails, a fusible link will break, shutting off the unit.
  • The flame failure system is used to shut the system off if the burner flame is not present.
  • If there is a power failure, the water heater will cut off the gas automatically.
  • In the case of an over-current, the power surge glass fuse will blow and shut the tankless water heater off.
  • Freeze protection includes electrical heating elements and intermittent firing of the burner.

Details and installation instructions can be found on the manufacturer's website.

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