How does a tankless water heater work ?

​If you grew up in a home with lots of people taking showers and running appliances, you’ve probably experienced what it feels like when that big tank runs out of hot water. Not too fun, is it? So how can this box, about the size of a suitcase, mounted to your wall keep your showers hot and your tubs full? It’s actually really simple.
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  • When the need for hot water arises by turning on a shower, washing machine, dishwasher or faucet, cold water flows into the Rinnai Tankless Water Heater from the inlet pipe at the bottom of the heater.

  • The flame is ignited and heats the two heat exchangers that are included in the Super High Efficiency models. 

  • Water is preheated as it passes through a stainless steel heat exchanger, capturing any extra heat (or latent heat) before it escapes into the vent system. 

  • Water continues to be heated as it passes through the heat exchanger, and exits from the hot water outlet pipe to travel through the pipes of the home to the water fixture where hot water is needed.

  • The tankless water heater will adjust flame output as needed to ensure the temperature set point is maintained.

  • As the hot water fixture shuts off, cold water stops flowing into the tankless water heater and the flame extinguishes. The tankless water heater is now off until the next time hot water is needed!

Super High-Efficiency Tankless Advantages
  • Gas ignites heat exchanger, which heat the water

  • Heated water exits hot water outlet to travel through pipes to where it is needed

  • Heater will adjust flame output as needed to ensure a temperature set point is maintained

  • Product lifespan of a tankless unit is twice as long as a traditional tank