The U.S. water heater industry is implementing a significant product design change that incorporates a new technology — flammable vapor ignition resistance or FVIR — that will help prevent problems caused by improper storage or use of gasoline and other flammable liquids near residential gas-fired water heaters.

As of July 1, 2003, new residential gas-fired units manufactured with storage capacities of 30, 40, or 50 gallons must meet American National Standards Institute (ANSI) standard, ANSI Z21.10.1-2001. (For details on the new standard, see the feature article “Water Heater Design Changes In The Works” in the July 21, 2003 issue of The News.)

Rheem’s Guardian System

The new Rheem Guardian System™ water heater not only meets the new ANSI standard, but also incorporates some unique design enhancements, says the company, including:

  • Air shutoff system: Like all FVIR water heaters, the Guardian System includes a flame arrestor plate to shield the burner and prevent its flame from spreading beyond the arrestor and igniting vapors outside the water heater. But the standard does not cover a sustained flammable vapor incident. Even shutting off the gas supply does not stop vapors from continuing to burn inside the water heater's combustion chamber.

    Because of this, the Guardian System's safety mechanism is designed to completely shut off the air supply to the combustion chamber whenever a flammable vapor incident occurs. This air shutoff system helps ensure that the water heater will shut down quickly and safely. Flammable vapors will starve and extinguish, so flames cannot spread beyond the combustion chamber.

    The Guardian System’s baffled air pathway causes a significant amount of LDO to drop away, preventing it from clogging the arrestor plate.
  • LDO filtration system: The key to long and efficient water heater life is to limit the amount of lint, dust, and oil (LDO) that can reach and clog the arrestor plate, says the company. The design of the Guardian System does this in three ways:

    1. Air flows into the combustion chamber from the sides, not from the floor where dust and dirt accumulate.

    2. One hundred percent of the combustion air is prefiltered by a unique intake design.

    3. The system's air pathway to the combustion chamber is guarded by special airflow baffles that prevent a significant amount of LDO from reaching and clogging the arrestor plate. (See illustration at right.)

    This three-way approach effectively prevents LDO obstruction, the company says.

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