GAS VALVES : SELF -ENERGIZED
One of the most common self- energized gas control valves is the sit manufacturing ,this millivolt control is available in three ignition configurations.
The first set up is for direct vent appliances that require fast acting flame failure response .
This configuration uses a split pilot flame with a thermocouple to energized the safety shot off and thermopile to power the main gas valve, this same split set up is used with the addition of an oxygen depletion sensor, pilot on tabletop patio heaters.this olds system disables the pilot and therefore the gas flow in the gas
Oxygen level drops below 18%.
These units are not designed to be used indoors.
The third is with thermopile only on gravity vented appliances that do not require rapid shut off in the event of flame failure.