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The Inner Workings of a Rheem IKONIC Condensing Tankless Water Heater

September 1, 2022
Rheem IKONIC tankless

Previously, we’ve demystified how condensing and non-condensing tankless water heaters function. The Rheem® IKONIC™ Super High Efficiency Condensing Water Heater with Recirculation, is the ultimate in convenience—and water savings—with unlimited hot water. Imagining how a compact, minimal clearance water heater can produce so much hot water quickly can seem difficult, but it doesn’t have to be. We’ll walk you through how the Rheem IKONIC unit functions.

How the Rheem IKONIC Condensing Tankless Water Heater Works

The Rheem IKONIC Condensing Tankless Water Heater works like a Rheem condensing tankless unit with a slightly different process and added benefits. A tankless unit heats water as needed instead of storing hot water in a tank. Combustion gas heats the water as it goes through each heat exchanger. Rheem condensing tankless units have an “Up Firing” system using dual heat exchangers. The water is preheated in the secondary heat exchanger that uses exhaust gases before traveling down to the primary heat exchanger situated above the burner. The Rheem IKONIC unit has a “down firing” design where the secondary heat exchanger is situated below the primary heat exchanger. The water travels from the secondary heat exchanger up to the primary where heat is transferred down from the burner.

  1. When a hot water faucet is turned on or when the built-in recirculation pump cycles water through the water heater, water starts flowing into the tankless water heater.
  2. Cold water entering the unit passes through the flow sensor, which activates the ignitor. The water then flows into the secondary heat exchanger, followed by the primary.
  3. The ignitor in the unit sparks before gas is introduced.
  4. The gas valve opens and sends gas to the burners to heat the water.
  5. Heat from the flame is transferred to the water in the primary heat exchanger. Any remaining heat is transferred to water in the secondary heat exchanger. Because so much heat is pulled from the combustion gases, condensation occurs which is acidic. Acidic condensate exits the unit through the condensate drain and should pass through a condensate neutralizer (sold separately) so it can be safely sent down the drain.
  6. Hot water exits the water heater and travels to the open faucet. Once the faucet is closed, the flow sensor stops detecting the flow and the water heater goes into a ready state. Our exclusive HotStart Programming™ feature will minimize cold water bursts if the faucet is opened again within five minutes.

Rheem IKONIC how it works

Combustion gases safely exit through a dedicated sealed vent system. For added efficiency, heat from the burner’s exhaust is absorbed in the secondary heat exchanger. The result is cooler exhaust and the ability to use PVC versus stainless steel as a venting material. Easy to install PVC venting saves in material and labor costs.

showerRecirculation in Tankless

Recirculation is a big part of why Rheem IKONIC is the new standard in tankless. It ensures on-demand hot water right from the faucet or shower. The Rheem IKONIC Condensing Tankless Water Heater with Built-In Recirculation Pump also has built-in EcoNet® Wi-Fi, which allows the homeowner to have complete control over the water heater from a smartphone, and built-in recirculation settings.

Homeowners have the option to program the recirculation pump to fit their household needs. Units with built-in Wi-Fi technology can be controlled remotely using the EcoNet app on their mobile device or with the on-unit control panel. For installations without a dedicated return line, a crossover valve can be installed to turn the existing cold water pipe into a return, allowing circulation back to the heater. This valve is easy to install and should be placed under the farthest sink. The pump will run until either the inlet water temperature reaches 107 degrees or for seven minutes. This eliminates the pump running constantly and reduces wear on the pump, particularly in larger homes.

More Tankless Information

We have some great resources that will help you understand tankless water heaters better. They will help you learn about how they may impact your everyday life. Find out more about the benefits, things to consider and all the details. Explore the Rheem tankless water heaters available.

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