Performed 1 system gas heat check up. Horizontal in attic. Talked to homeowner about where he could find better 20x30x1 air filters. Currently using merv 1 every 30days. Oddball size. Furnace in the attic is heating well. Only 2 yes old. Cleaned flame rod, confirmed all motors are working properly. Condensating furnace has a clear drain line and good slope. No issued for furnace. Set back to cooling and condenser turned back on.