Performed QA on Trane Heat Pump/Gas Furnace system. Homeowner had a lot of questions on the operation of the system. He also mentioned the house has always had a musty smell from the basement. The basement is almost completely crawl space. Talked to him about sealing the crawl space area and duct sealing as areas he may want to look into. I went through the system and made adjustments to the cycle per hour and the compressor minimum run speed. Answered all of his questions and reviewed the system settings and the operation of the system with him. Tested the system in heat pump and gas furnace heating. Tested the humidifier operation. Completed checklist form in system. The Knob for the humidifier damper was missing. Need to order a new Damper for a 600M Humidifier. This can be replaced at the Six Month inspection. Humidifier is working and it is not affecting anything right now.