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Item #: 73470
Discontinued, here is a link to similar thermal protectors.
Leviton 9454-D35 120v 7.2k 135'C thermal protector
Snaps into 1/2 knockout, 7.2k 120v 135'c thermal protector with 6" leads
This wires in addition to the socket and/or ballast and will turn the unit off once it reaches a temperate higher than what the thermal regulator is rated for. Thus preventing the application from letting the bulb overheat
To test you would need to have an ambient thermometer and over heat the area of the thermal protector to be higher than what the unit is rated for. Then it would shut the application off until it was below that temperature.
It should not be hot, it may be warm.
Yes this is compatible