American Tankless Water Heaters
Review and Buying Tips

An expert review of the American tankless water heaters for on-demand water heating in residential and small commercial applications. Explore the main advantages and benefits of the condensing and conventional tankless models from this well-known HVAC manufacturer.

American water heaters with tankless technology are designed for efficient on-demand heating and continuous supply of hot water in residential and light commercial applications. They are available in several sizes, covering smaller homes and apartments to large homes with multiple bathrooms, even for heating hot tabs and space heating. Due to its wall-mount and compact design, tankless heaters occupy much less space than conventional, resulting in additional storage.

American tankless water heaters are designed with full power modulation, making them ideal for the point-of-use and whole-house water heating, and offering superb features and components, as found in top-selling and popular brands, such as Rinnai, Noritz, or Takagi.

Models review

American tankless water heater

The American manufacturer offers a decent number of tankless models for potable water heating, six non-condensing models, and three Energy Star compliant condensing models. All models are designed to use natural or propane gas:

  • GT-110/110C/110U NI/NE (indoor/outdoor)
  • GT-310/310C/310U NI/NE (indoor/outdoor)
  • GT-510/510C/510U NI/NE (indoor/outdoor)
  • GT-240H NIH/NEH (indoor/outdoor)
  • GT-340H NIH/NEH (indoor/outdoor)
  • GT-540H NIH/NEH (indoor/outdoor)

American non-condensing tankless models

American GT-110

American tankless water heaters from the GT-110 series are the smallest conventional tankless models designed for residential water heating in apartments, cabins, and homes with up to two bathrooms.

The modulating gas valve allows them to work in the power range between 19,500 and 140,000 BTU and provide a maximum of 6.6 gallons of hot water per minute. One of the greatest benefits is the lightweight design and installation flexibility - the 110 series can be installed indoor using power or power direct venting or outdoor as ventless.

American GT-310

The 310 series comes with a gas input ranging from 11,000 to 190,000 BTU and higher capacity than the previous model, 8.0 GPM, which makes them great for homes with up to three showers. Like the earlier models, these are available for residential indoor and outdoor installation, including direct venting.

American GT-510

Water heaters from the 510 series are the strongest models in this non-condensing group, and they utilize a more robust heat exchanger made of the strong HRS35 copper alloy. This allows American tankless water heaters from 510 series heavier usage and not only in residential but commercial applications.

Water heaters are designed for potable water and space heating and recirculation systems due to their ability to use circulation pumps.

As opposed to the two previous series, tankless water heaters from the 510 series can be combined through the Easy-Link or Multi-Link systems to provide more power and higher water flow.

All models can provide the maximum water flow of 10 GPM, making them great for homes with up to four applications while changing the power from 15,000 to the maximum of 199,000 BTU - thanks to the modulating gas valve.

Moreover, this is not the end of the impressive features this group offers because water heaters from the 110U, 310U, and 510U series are designed to meet ultra-low NOx requirements and contribute significantly to environmental protection. Some models utilize concentric venting making installation faster.

American condensing tankless models

American tankless water heaters with condensing technology are ultra-high efficient units equipped with the secondary heat exchanger to utilize the latent heat from the flue gases. All indoor models come with the temperature controller as the standard feature, while the outdoor units include a wall mount controller type.

This technology allows them to increase energy efficiency, which can go as high as 95%, vs. 82% for non-condensing models. All the condensing models come with ultra-low NOx gas combustion.

American GT-240H

GT-240H models are, with the maximum water flow of 6.6 GPM, the smallest condensing units available, designed for installation in smaller homes, apartments, condos, and cottages. The gas input is from 13,000 to 160,000 BTU, and thanks to the high-efficient gas combustion, the energy factor is 0.95.

American GT-340H

The GT-340H series, as the above groups, is available for indoor and outdoor installation, also direct venting, and can modulate its power from 13,000 to 180,000 BTU while providing the maximum water flow of 8.0 GPM, enough for supplying hot water to 3 fixtures simultaneously.

American GT-540H

Indoor and outdoor water heaters from the GT-540H series are designed for larger homes with more than three showers or bathrooms, as they heat water with the maximum power of 199,000 BTU and provide a water flow of 10 gallons per minute.

These tankless units are recommended not only for residential but commercial applications due to their commercial-grade heat exchanger, robust design, and exceptional resistance to mechanical and thermal stress. As the above 510 series, the 540H series can also use the Easy-Link and Multi-Link system and connect up to 20 units. Only this group can increase the temperature up to 185 F while other models up to 140 F.

Similar model: Rinnai RUR98 (sold on

Product features


All tankless water heaters from American, either non-condensing or condensing, are high-efficient since the thermal efficiency goes from 84% to high 95%, but only condensing water heaters are Energy Star compliant.

Heat exchanger

Heat exchangers are built strong for better performance and long life. For example, condensing water heaters have one primary HE made of the commercial-grade copper HRS35 and the secondary, made of high-quality 316L stainless steel. The above materials' great quality and characteristics make the heat exchangers resistant to corrosion and high thermal stress.

Water flow

Models are built in various sizes so that they can provide enough hot water from smaller homes, apartments, condos, or cottages to larger houses with several bathrooms. This is possible since the water flow goes from low 6.6 to high 10 gallons per minute, and with the help of the connecting cable or connection kit, more units can be combined into one system.

Features such as Easy Link and Multi-Link, as found in 510 and 540 models, allow you to connect up to 4 or up to 20 units so that you can get even more hot water - great for high-demanding applications such as hot tubs.


American tankless water heaters can be installed indoors or outdoor, depending on the type you are buying. The indoor models are very safe since the unit has the sealed combustion, so no interior combustion air is used for gas burning. The venting system makes them very flexible, as they can be installed far away from the exterior walls (up to 100 ft.). All models are factory built to use natural gas and converted to use propane or LG gas.

Temperature controller

The built-in temperature controller found in indoor models is handy and convenient. The outdoor models come with the wall mount remote. With the precision of +/-2 degrees, it allows you to change and monitor the temperature of the outgoing hot water and diagnose problems, get the error codes for easier repair and readings such as the energy usage, water flow, etc. The temperature can be set on the remote controller from its minimum of 99 F to the maximum of 140 F, or 185 F on some models (510 and 540H series, for example).


Tankless water heaters are equipped with electronic ignition to light the gas burner automatically, and as soon as the hot water tap is opened.

Safety features

To provide safe and reliable work, the American Company offers several safety features to protect its gas-powered tankless water heaters:

  • Air-Fuel Ratio (AFR) sensor - helps to maintain the proper and clean combustion.
  • Overheat protection – used against high temperature utilizing the Hi-Limit switch.
  • Flame failure protection – reacts when the burner flame is extinguished.
  • Power failure – reacts when the unit loses power.
  • Overcurrent protection.
  • Fusible link – activates when overheat protection fails to protect the water heater.
  • Internal freeze protection - includes electrical heating elements that keep water temperatures inside the heat exchanger above the level that prevents freezing.
  • Onboard circuit board - controls all the functions from above.


American tankless water heaters for residential use come with 15 years warranty on the heat exchanger and five on all other parts, while in the commercial application, the warranty is 10 years.


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