FVIR WH Inspection Tips


April 2008Flammable Vapor Ignition Resistant (FVIR) Water Heaters
by Don NormanThis month we have a guest inspection tip author, Don Norman, Manger of Home Inspection and Contractor Education.
By now, you’ve seen Flammable Vapor Ignition Resistant Water Heaters or FVIR water heaters. A review of these components and how to inspect them is warranted since they have evolved since this tip was originally published in 2004.
The Water Heater Joint Research and Development Consortium (WHJRDC) developed new water heater technology that solved the problem of flammable vapor ignition associated with gas water heaters. The (relatively) new water heaters meet the ANSI Z21.1.1-2001 standard that states the water heater “shall not ignite flammable vapors outside the water heater created by the spilling of…gasoline onto the floor”. A study by the Consumer Products Safety Commission (CPSC) identified almost 2000 fires as a result of water heaters resulting in 17 deaths and 316 injuries through 1994. About 75% of these fires were related to improper storage or handling/spillage of gasoline.
With compliance to FVIR standards, these water heaters no longer have to be elevated in garages and similar locations unless required by the manufacturer or local code authorities. Most codes have already been updated to reflect the FVIR technology starting in 2002 with the 2002 National Fuel Gas Code and the 2003 International Fuel Gas Code.


The water heaters incorporate new technology that helps accomplish the requirements of the new ANSI Standard. This technology consists of:

  • <LI class=maincopy>A device to prevent ignited vapors from passing out of the combustion chamber <LI class=maincopy>A one way intake system to control the movement of makeup air into the combustion chamber

  • An inner door and burner assembly to create a sealed junction with the combustion chamber, preventing combustion air and flammable vapors from entering the chamber through the front of the water heater
    While all manufacturers differ slightly in design and how to accomplish the desired outcome, they all have the following FVIR features in common:

  • Flame arrestor plate. Located under the burner, this plate is designed to allow combustion air into the combustion chamber but keep flames from escaping downward and igniting flammable vapors below. This plate is a key element of the FIVR technology and might also be called an arrestor plate or a flame arrestor.
    <LI class=maincopy>Thermal cutoff. This is a switch designed to shut the unit down if it senses excessive temperatures caused by inadequate combustion air inside the combustion chamber. Inadequate combustion air can be caused by ignition of flammable vapors, inadequate venting, inadequate makeup air or the accumulation of lint, dust or oil on the LDO screens.

  • Lint, dust or oil (LDO) screens. This screen is to protect the combustion process from lint, dust or oil. This screen was added after it was determined that LDO contamination could adversely affect the system. The openings in the screens are subject to dirt accumulation especially in basements and utility areas. As part of the FVIR certification process, water heaters must shut down before exceeding carbon monoxide (CO) limits.
    The FVIR water heater phase-in began in July, 2003 and was phased in over the next two years. Existing inventories of conventional water heaters were allowed to be used until the inventory was exhausted. Implementation of the phase was in 3 stages. PHASE 1: July 1, 2003: 30, 40 and 50-gallon atmospheric vent models. Manufactured housing models were excluded. **PHASE II: July 1, 2006(revised) **30, 40 and 50-gallon power vented models. Manufactured housing models were excluded. PHASE III: July 1, 2007 All other gas-fired models with inputs of 75,000 BTU or less.
    When inspecting the water heaters, we proceed as always with one exception. We should be checking the outer jacket for physical damage and evidence of leakage. Check the draft at the draft hood and maker sure the flame pattern on the burner is the typical blue gas flame seen on previous models. The inner factory sealed combustion chamber door, however, should not be removed. A small window allows us to view the burner in operation.

For more information check out GAMA’s Consumer Information on New FVIR Water Heaters or any manufacturer Web site. Two of the larger water heater manufacturers are State and Rheem.

Be careful out there.

I don’t necessarily agree with all of this info and still advise elevation when installed in the garage, jmo

There are a lot of people very unhappy with the FVIR water heaters due to the fact that the one time fuse built within the thermocouple blows because the air intake screens get plugged up.
It’s not cheap to have the thermocouple replaced.

BS’ing with other plumbers around the wholesale houses*, I heard *that Lowe’s was giving away replacement thermocouples for a while but then started telling people “read your manual, it says you must clean the screen every so often”.


Dust bunny kills FVIR

:mrgreen: :mrgreen: :mrgreen:

The “factory sealed combustion chamber door” seals on the burner cover according to Peoples Energy around here have to be replaced by new ones when you open the “sealed door” so that could be why Don Norman
suggests NOT to open it. You check you may wreck…:smiley:

What do you mean I have to clean my place???:roll::D:D