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Energy-Efficiency Enhancing Technologies: Electronic (Interrupted) Ignition

A standing pilot light, which burns gas continuously at a rate of approximately 400 Btu/h, is the most common ignition system in gas-fired storage water heaters. Available electronic ignition devices include:

  • an intermittent pilot ignition device that by generating a spark lights a pilot, which in turn lights the main burner
  • an intermittent direct ignition device that lights the main burner directly by generating a spark
  • a hot surface ignition (HSI) device that lights the main burner directly by generating a hot surface

Unlike standing pilots that consume gas continuously, these devices operate only at the beginning of each on-cycle. Although there is no increase in the steady-state efficiency with use of electronic ignition devices, the overall fuel consumption may be reduced. Burner on-time may increase to make up for the heat the standing pilot would have supplied during standby periods.

Electronic ignition devices require an outside electricity source for ignition, usually a 24 V or a 120 V system. The power draw of the electrically operated gas valve is between 5 W and 12 W, and power is consumed only when there is a call for heat. Electronic ignition systems also require a control module, which houses the electronic control circuitry and consumes 6 W of power during a call for heat. These systems also need an electronic thermostat that draws 1.2 W of power during the heating period and 0.4 W of power during the standby period. The HSI (Hot Surface Ignition) is a resistive device that draws about 2.5 amps at 120 V (about 300 W of power) for approximately 30 seconds during ignition.