It was a warm August day, myself and my co-worker were digging into some PM work.  We found one of the Carrier RTUs without power and the breaker tripped.  

"This one time, at band camp," is a famous line you may remember from the movie American Pie.  Although the narrative, as it pertains to this article goes as such, "this one time, in residential". 

Expansion valves are used to inject refrigerant into the evaporator of refrigeration and AC/HP systems at a condition that will allow the refrigerant to absorb heat.