Customer Care > FVIR design

A Major Design Initiative

State Water Heaters FVIR design for gas water heaters meet the standards and testing protocols established by the American National Standards Institute (ANSI) that deal with the accidental or unintended ignition of flammable vapors, such as those emitted by gasoline. State residential water heaters meet the ANSI standards in accordance with the schedule in the right hand column.

Introduction Schedule

PHASE 1: 01 July 2003
30, 40 and 50-gallon atmospheric vent models. Manufactured housing models are excluded.

PHASE II: 01 July 2006
Power Vent C3 Press Release

PHASE III: 02 July 2007
All other gas-fired models with inputs of 75,000 BTU or less.


On July 1, 2003, all residential gas water heater manufacturers introduced 30, 40 and 50-gallon atmospheric models with "Flammable Vapor Ignition Resistant" design. Every manufacturer's design must meet standards and protocols established by the American National Standards Institute (ANSI Z21.10.1). And, while all manufacturers' designs are unique in some respects, all incorporate the following features:
  • A Flame Arrestor, located beneath the burner, designed to permit combustion air to flow up through it to sustain combustion, but to prevent flames from escaping downward through it in the event of flammable vapor ignition.
  • A Thermal Cutoff switch (TCO), designed to shut the unit down when it senses excessive temperatures caused by inadequate combustion air inside the combustion chamber.

There are several facts inherent in the Industry's testing protocols for Flammable Vapor Ignition Resistant Certification that you must keep in mind:

1.  All designs use Flame Arrestor technology to prevent a back-flow or back draft of ignited vapors.
2.  All flame arrestors are susceptible to lint, dust or oil (LDO) accumulation in harsh environments.
3.  All water heaters must shut down before exceeding Carbon Monoxide (CO) limits to pass LDO testing.
4.  All designs have a temperature sensor to shut down the water heater. An abnormal situation, creating a "shut down" condition, can be caused by the accumulation of LDO, ignition of flammable vapors, inadequate make-up air for combustion, or inadequate exhaust venting. These conditions (except for ignition of flammable vapors) can cause the burner flame to flatten out and increase the internal temperature of the water heaters' combustion chamber.

State Water Heaters use FVIR design


The key differentiating elements of the FVIR design design beyond the competition are:
  • Only the Corderite Flame Arrestor is fireproof, will not retain or conduct heat, and will not warp!
  • The FVIR design design incorporates a Corderite flame arrestor that has very low thermal conductive properties. It does not absorb heat and it will not warp.
  • The FVIR design Flame Arrestor

    Only FVIR design water heaters feature a scientifically designed lint, dust and oil screen, which can be easily inspected and cleaned.

    To prevent particles of lint, dust and oil from clogging the flame arrestor, FVIR design water heaters are the only ones equipped with a removable LDO screen mounted in the combustion air inlet port at the bottom of the water heater. If LDO particles have accumulated, the screen can be easily removed and cleaned, using a soft cloth or warm soapy water.


    The FVIR design Air Intake Screen


    FVIR design Gas Water Heater design simplifies parts replacement.

    FVIR design gas water heaters feature a single, self-contained pilot burner assembly, which includes the thermocouple and the temperature sensor. If service or replacement is required, there's only one part to deal with, with no guesswork as to which component is causing the problem. FVIR design is the most contractor friendly FVIR design on the market. And, of course, a design that saves the contractor time ultimately saves his customer money.

    FVIR design Gas Water Heaters are the only units that are Self-Resetting.

    There are a number of conditions that can deprive a gas water heater of adequate make up air for combustion. These include improper installation, air exhaust situations from attic or other exhaust fans in operation, and LDO accumulation. These can prevent adequate make up air from reaching the burner in an "FVIR" gas water heater.

    When such conditions occur, the FVIR design temperature sensor is self-resetting. In other words if the sensor detects poor combustion conditions, it shuts down the water heater. Then, once the water heater has cooled down, the sensor automatically re-sets itself. This allows the water heater to be easily restarted, after the cause of poor combustion is corrected.