Review: Rheem RTG-64XLN Low NOx Outdoor Tankless Water Heater

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Water waste is one of the biggest issues in the tankless water heater industry today. For the appliance to trigger on, most models must sense a specific flow rate to begin heating the water. The Rheem RTG-64XLN Low NOx Outdoor Tankless Water Heater offers users one of the lowest flow-rate triggers that is available right now. It will begin heating water at just 0.40 GPM. That’s at least 20% lower than most other models that provide a similar service.

This is an outdoor-use only water heater, but it does feature next-gen burner technologies so you still receive a highly efficient appliance. If all you need is a 35-degree shift in water temperature, then you can expect a GPM of 6.8. A 45-degree temperature increase results in a GPM rating reduction to 5.3. In colder climates that need 60+ degrees Fahrenheit of adjustment, the flow-rate can be sub-4.0.

Features of the Rheem RTG-64XLN Tankless Heater

  • This is one of the few tankless water heaters that is designed to operate at high altitudes without any special adjustments. In the standard configuration with minor adjustment, it can operate at nearly 10,000 feet above sea level.
  • Although it is an outdoor-only tankless water heater, it does meet the SCAQMD rules for ultra-low NOx emissions.
  • There is an overheat film-wrap that has been included with this unit so the heat exchanger receives and extra level of protection. The heat exchanger is also one of the few in the industry today that has an all-copper design.
  • This Rheem model has been given an efficiency rating of 0.82.
  • It offers a 0.26 GPM minimum flow rate, which is one of the best that the industry has to offer, without activation.

Since this is an outside-only model, many homeowners gain an advantage because there isn’t the cost of a venting installation like indoor models tend to have. You will, however, need to have a ¾-inch gas line, which may require an upgrade.

What to Expect with the Rheem RTG-64XLN Tankless Heater

The remote is included with this tankless water heater instead of requiring a separate purchase, which is surprisingly difficult to find with this type of product. You can adjust temperature levels or power down the unit with your remote.

We were able to achieve water temperatures of about 155F when this unit was on its max setting. That was an 80F-degree temperature change, which gave us a flow rate that hovered right around the 4 GPM range. Setting it between 120-140F let us approach 5 GPM.

If you need to provide weather-resistance to this unit, it is necessary to provide venting for any cabinet that may be installed. You may also need to remove snow from those vent ports to prevent the pilot light from going out.

We found this to be an excellent product. The Rheem RTG-64XLN Low NOx Outdoor Tankless Water Heater is consistent and would work well for smaller families and homes. It is definitely worth the investment.

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