Whatever amount of time the umpires deem reasonable. For example, Mercury vapors take take 5 to 10 minutes to cool down enough before they will begin to restrike, then 3 to 5 minutes to come back up. If all you had to do was restart them that is 15 minutes minimum. I was working a plate one night and the ice machine overheated the breaker panel and caused part of the lights to go out. I had to go in and replace several breakers myself because I was the only one with the knowledge to do it.