This week I was wondering how long it would take a pilot light to deplete a tank of LP fuel (the kind people use for grilling.) Several months? A year? For no particular reason, I wondered what the limitations would be on shrinking the pilot light. Could a small tank keep a flame going for 10 years? 100 years? I sense one challenge would be machining a small scale nozzle for laminar flow, and carefully filtering both fuel and air inputs to ensure the tiny nozzle didn't clog, for instance, with a grain of sand, or a piece of pollen. At a small scale, what are the limits of flame?

This article scratched an itch.

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amluto 6 hours ago | parent [-]

A pilot light is tricky: in typical designs, it needs to heat a thermocouple enough to produce enough current to drive a solenoid to allow the rest of the flame to ignite. Thermocouples are outrageously inefficient.

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NetMageSCW 3 hours ago | parent [-]

The pilot lights I’m familiar with just light the rest of the flame directly since they are burning already - turning on the fuel is all that is required. What systems uses a thermocouple and a solenoid?

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compiler-guy 2 hours ago | parent | next [-]

Approximately all gas appliance pilot lights.

https://www.acservicetech.com/post/how-the-gas-pilot-light-f...

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bob1029 3 hours ago | parent | prev | next [-]

I've got a Honeywell digital controller on my hot water heater. It's powered by the thermocouple. It can make troubleshooting a lot easier because it has flashing lights for diagnostics.

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amluto 2 hours ago | parent | prev [-]

It’s extremely common for the mechanism that only allows the fuel to be turned on if the pilot is lit to work by having a thermocouple in the pilot flame. Some of these also power the controls (thermostat, for example) and some don’t.

	▲	throwway120385 an hour ago \| parent [-]
		Yeah blowing yourself up with a gas leak is common enough when you're working on these systems that it's pretty important to have an interlock there.