New gas water heaters are safer than the older types.

by stewart wrozier

The 40 and 50 gal gas water heaters mfg after 2003 are FVIR water heaters. Flame Vapor Ignition Resistant water heaters will protect you from any combustible vapors around the water heater that could catch fire. They work the same heating your water but the air intake is different and requires preventive maintenance. Keeping the air intake screen or flame arrestor clean is the only thing, but very important.

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May 13, 2010
FVIR and gas water heaters
by: Zee from water heater reviews

All gas fired residential water heaters that are atmospherically vented with the BTU ratings of 75,000 or less are required to be FVIR compliant.

Flammable Vapor Ignition Resistant design includes not only a flame arrestor, but LDO screen (lint dust and oil) and TCO limit or thermal cut off switch.

LDO screen protects the flame arrestor from lint, dust and oil that can enter the combustion chamber with the combustion air. If LDO and flame arrestor are dirty, you might have a poor combustion which results in yellow flame, sooting and carbon monoxide production. There will be lack of oxygen and the pilot light on your gas water heater goes out.

With the blocked screen the pilot light goes out also due to the increased temperature in the combustion chamber which will result the TCO to open the automatic reset.

Flame arrestor is usually made of fireproof ceramic material and is built into the base of your gas water heater. Combustion air passes through the small ports of the flame arrestor and further to the combustion chamber.

Use the vacuum and remove any blocking material from the flame arrestor and LDO screen.

TCO is the thermal cutoff device and is part of the thermocouple. TCO is an automatic reset thermal switch and if the temperature exceeds pre-set, or is between 160 and 200 C it will open thermocouple circuit and turn the pilot and the main burner off. The excessive temperature is the result of flammable vapor ignition presence inside the combustion chamber and when the clogged LDO and flame arrestor are blocking the combustion air to enter.

Manufacturers like Reliance are designing the pilot burner assemblies where TCO is the integral part, so if needs replacement, replace the whole assembly.

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