Standing Pilot - Short #228

HVAC School - For Techs, By Techs

In this short podcast episode, Bryan talks about the standing pilot gas systems and the ignition strategy in gas-fired appliances.

Standing pilots are very simple devices that are common in fuel logs, water heaters, and some pool heaters. These devices have a thermocouple or thermopile; in a thermocouple, two dissimilar metals are connected at one end, and there is an electron flow between the metals when one is heated up. A thermopile is a collection of thermocouples in series or parallel to generate more millivolt signals. (Both of these can be damaged if cleaned; don't mistake these for the flame rod! Flame rods can be cleaned with a delicate material.)

To use a standing pilot, turn the dial to the pilot mode and press it in, which allows gas to come through the pilot. Then, you can light the gas (with a lighter or spark mechanism) and keep the dial depressed until there is enough heat generated on top of the thermocouple or thermopile, which allows it to lock in and keep the pilot lit (and pass the entire safety circuit). Then, you turn the gas valve on and let the main burner take over.

If one safety is open, the entire circuit breaks to prevent unspent fuel from accumulating and causing a dangerous condition. One of the main challenges with standing pilots is that they are prone and very sensitive to corrosion due to the low voltage and current. Clean and tight connections can mitigate these risks.

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