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What is an FVIR water heater?
Friday, July 20, 2018
Gas fired water heaters were required for many years to be elevated a minimum of 18-inches above the floor when installed in a garage, because of the possibility of the flame at the base of the water heater igniting gasoline vapors from a car parked in the garage or any of the other flammables that are commonly stored there. Gasoline vapor is heavier than air and tends to collect near the floor, so the requirement made sense. But there were still thousands of house fires attributed to water heaters each year.
As a result, design changes were mandated by the Consumer Products Safety Commission (CPSC) and all 30, 40, and 50 gallon gas-fired water heaters manufactured after July 1, 2003 have been required to have Flammable Vapor Ignition Resistant (FVIR) technology. It’s also worth noting that a group of manufacturers helped develop the standards and began voluntary implementation of the technology before it was required.
FVIR water heaters are specifically designed to prevent “flashback” vapor ignition fires in three ways:
- Only one-way flow of air into the combustion chamber.
- A flame arrestor plate to prevent any ignited vapor from passing out of the combustion chamber.
- A sealed burner compartment door assembly.
The American National Standards Institute (ANSI) established standard ANSI 21.10.1a-2002, effective July 1, 2005, that further defines the requirements and applies to all water heaters of 75,000 BTU or less. Because FVIR water heaters have a closed combustion chamber, you can no longer open a panel at the base and reach in with a match to light the pilot.
If any flammable vapors do manage to get into the combustion compartment, they are ignited in the sealed chamber, and the flame arrestor plate keeps any flames from escaping. Each manufacturer has their own slightly different design for FVIR safety, and they now have incorporated features that shut of the flow of gas and seal off the combustion air if a flammable vapor event occurs.
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