FLAME LOCK® Gas Water Heater Operation

FLAME LOCK® Certification

Spills of gasoline, or the presence of other flammable vapors, near a standard gas water heater can be very dangerous.

The American National Standards Institute (ANSI) now requires all residential water heaters to be flammable vapor ignition resistant (FVIR). All FLAME LOCK® water heaters are fully compliant with ANSI FVIR standards.

FLAME LOCK® water heaters have a sealed combustion chamber. Combustion air and flammable vapors can only enter through a specially designed flame trap. The flame trap is located in the bottom of the combustion chamber, under the main burner and pilot flame. If flammable vapors are present, the pilot or main burner immediately ignites them inside the combustion chamber.

The vapors burn on top of the flame trap and are prevented from escaping back into the room. When the vapors become too rich or too lean to burn, they snuff themselves out.

Just like with electric water heaters, many options exist for gas water heaters, including the type of gas used, the amount of heat generated (referred to as Btu output), the altitude at which the unit may be operated, the type and sizing of the venting, and whether the unit has power venting or not (determines where in the residence the water heater may be located).

A second part of the ANSI Standard concerns resistance to lint, dust, and other debris build up on the flame trap. If the flame trap were to become clogged, combustion air would be reduced, starving the burner of oxygen. This may increase the amount of carbon monoxide exhaust and create a health hazard. FLAME LOCK® water heaters are designed to reduce lint buildup. The small pressure wave created by lighting the burner during normal operation helps blow lint off the flame trap. If lint does build up, the thermal cutoff switch will shut down the heater, so the flame trap and the filter may be cleaned.

The control circuit for a FLAME LOCK® water heater is similar to a standard gas water heater. The main difference is the addition of a resettable thermal cutoff switch (see Figure 2) to the thermocouple circuit.

If flammable vapors are ignited, they will trigger the thermal switch, cutting off the gas supply to the pilot and burner. This prevents the vapors from being reignited after they have self-extinguished. A water heater that has experienced a flammable vapor event, in which the thermal switch has cut off the gas supply, should be returned to the manufacturer and will be replaced. In such situations consumers should call the support number provided on their water heater jacket, or in their warranty documentation, for details.

Insufficient combustion air supply or blocked ventilation can also activate the thermal cutoff switch. When these conditions have been corrected, the thermal switch can be reset, and the heater returned to normal operation.