Tankless water heater
What it is
An ENERGY STAR certified gas tankless water heater uses a secondary heat exchanger to use 9 percent less energy than a conventional gas tankless water heater.
Most fuel-fired tankless water heaters are direct vent and many are sealed combustion. Exhaust gases are blown directly out through a vent in the wall, not up a flue or chimney.
tankless water heaters are constructed of less galvanically active metals to protect them from corrosion. This is because tankless water heaters cannot employ an anode rod to protect against corrosion.
Most tankless water heaters are sealed combustion, meaning that combustion air for the burners is brought directly from outdoors and the combustion fumes are exhausted to outdoors without any interaction with the living space air.
A gas tankless water heater’s basic components include a high-powered burner, fan, and heat exchanger. When a hot water tap is turned on, cold water enters the unit from the cold water supply and a sensor detects the water flow; then it activates a heating device, which raises the water temperature to a preset level.
ENERGY STAR · U.S. Department of Energy · Pacific Northwest National Laboratory
Its parts
- Burner
- Basic components of a gas tankless water heater include a high-powered burner, fan, and heat exchanger; condensing gas water heaters also have a secondary heat exchanger and a piped air intake to the sealed combustion chamber.
- PVC vent
- The secondary heat exchanger extracts more heat from the combustion gas, cooling it to the point where there is condensation – hence these types of heaters are called “gas condensing.” These gas condensing tankless water heaters, like gas condensing furnaces, require venting through a vertical PVC pipe and a condensate drain.
If it may be unsafe
If you smell gas, leave the house and call Peoples Gas at 866-556-6002 or 911 from outside. If your CO alarm sounds or anyone feels sick, leave and call 911 from outside.
AirLogic is not an emergency service.
Related pages
- Glossary: Tankless water heater
Its entry, and the guide's pages that use it.
- Gas water heaters
Gas water heater types, burning air, venting and the signs of backdrafting
Sources
- ENERGY STAR. How It Works - Whole-Home Gas Tankless Water Heaters.
- U.S. Department of Energy. Gas-Fired Tankless Water Heaters.
- Pacific Northwest National Laboratory. Impacts of Water Quality on Residential Water Heating Equipment (PNNL).
- U.S. Department of Energy. Tankless WHs Gas Fired.