Normally you push it in and hold it while you light the pilot light. Then after it has warmed up you can turn it to on. There is a heat sensor there so if the flame gets blown out it will not keep flowing gas.
It's called a thermocouple
Depends. Most of the newer ones are electric pilots, so they spark to get the flame started ... considered safer since you don't have a flame on when not in use.
Really? I don't think I've ever seen a water heater with electric ignition
The common term, "hot water heater" always amuses me. Hot water does not need heating. It is cold water that needs a heater, to make hot water.
We have a strange language. :facepalm:
It's called a thermocouple
In the thermocouples used in most water heaters, the heat from the pilot light will generate a current measuring 20 millivolts in the thermocouple circuit. This voltage is sufficient to control and hold in the "open" position the gas control supply valve to the pilot.
Yes, but it's not actually a thermocouple. It's a capillary in which the fluid expands when heated, sufficiently to push open a valve in the main gas line. When you turn to "on", you open a second valve in that same line and gas is free to flow into the burner.
An actual "thermocouple" is a junction of two dissimilar metals which produces a small voltage related to its real-time temperature. These require some electronic circuitry to convert that information into a usable function. Capillary systems don't require that, and thus are less expensive to make.
Try to buy a capillary at the appliance parts store.
Despite an evolutionary change in the "where used", it was an excellent description of a thermocouple nonetheless...Wow! I guess I've been out of that particular loop for too long! I stand corrected!
Thanks guys.
Busted by the thread police....