Arrived on site to perform maintenance on Lennox unit. Cycled system for heat. Verified proper heating sequence of operations. Temperature rise is on higher end of allowed range. Ran system through 20 point inspection. Tested electrical components and heating safeties. Unit has a drain duct connected to plenum end cap, which is bad for airflow to remaining ducts. Insulation levels are also extremely low in attic. Went over findings and recommendations. System operational upon departure.