Clever mechanism, T&P valve, Wax Actuator

Teardown of a T&P valve to learn how it works.
Edit 7/1/2023, turns out these are called wax actuator/motors. Thanks ‪@aeroderek‬ !
‪@TechnologyConnections‬ you should do a video on wax actuators!

[@aeroderek]

I would expect that it is a wax actuator. Basically you blend waxes to make different temperature set points. Then when it hits that temperature, it will expand a lot. Probably a phase change involved.

[@gjackets]

Wow I have never heard of a wax actuator. Surprisingly used in a lot of applications. Thanks for sharing!

[@sbly318]

Incredibly informative!

[@gjackets]

Glad you enjoyed it

[@Sparky-ww5re]

I assumed it was a wax motor. A mixture of different wax blends results in very predictable and melting points. Essentially when the wax melts it expands suddenly, pushing against the piston and opening the valve full force and remaining open until the probe cools a certain number of degrees below 210°F. This dumps the overheated water, allowing the cold inlet to fill the tank with cold water, thereby safely lowering the temperature and preventing the water heater from becoming a bomb in case the thermostat failed to shut off the heat after the setpoint is reached. Once the T&P valve cools and closes, the water will again overheat and the cycle repeats itself until the overheating problem is resolved
The wax motor is used in many other applications. The thermostat that keeps the engine in your car operating at a consistent temperature uses a wax motor that is partially open under normal engine temperature and operating conditions. This allows for additional cooling capacity if driving conditions change (towing a trailer, driving up steep mountain grades, unusually hot or cold weather)
Fire sprinkler heads with the red liquid inside a glass tube also use the same principle as the wax motor. Sprinkler heads come in various temperature ratings from ordinary (135 - 155°F) to 650°F (ultra high) . When the temperature of the glass tube exceeds the temp rating, the wax/liquid expands and breaks the glass, activating the sprinkler.

[@gjackets]

Yep I think you got it. It's a wax actuator/motor in a T&P valve. I've never heard of them before. Pretty awesome design. Thanks for sharing