How an Indirect-Fired Water Heater Works
  • Your boiler circulates hot water to a coil inside the water heater.
  • The heat from the boiler’s hot water transfers from the coil to the water in the tank.
  • This system is most efficient in the winter when the boiler is being used to heat both the home and domestic water. In effect, no extra energy is needed to heat your domestic water — as opposed to a traditional water tank with its own oil or gas burner or electric heating elements.