Upon arrival checked in with Mr.Cheney and located unit in the attic which has the overflow to the emergency drain pan by the front door. Since system already had blow out valve ran pressurized nitrogen through primary condensate line which terminates by the outdoor condenser. After drain line was clear ran secondary drain port to the emergency drain pan since it was capped off to prevent water from overflowing in the interior pan. Recommend re routing drain lines to a better spot.