Originally Posted by
Brent Crouse
I'm confused. If the condensate lines run directly outside, why do they need a p-trap?
Brent,
To keep air from moving into, or out of, the AHU.
If the AHU is a blow through style, it will blow air out through those condensate lines unless there is a trap sufficiently deep enough to resist the static pressure.
Likewise for AHU which as suck through, except that they will suck air in (instead of blowing air out).