Sully is hands down a professional in all sense of the word. His background is in commercial as well as residential. He is committed to doing the job right and also committed to all the necessary regulations required for safety.
He pointed out an old job that was done whereby my former humidifier water tube was as safety hazard to the furnace's 25 volt electrical point. Ya that's the kind of guy I want working on my home one that thinks to look at hazards that could cause big problems.
Ask away your questions, he's going to tell you the straight goods and another thing, a furnace is just like your car... if its 20+ years old its not going to keep running along with all the moving parts on just oil changes and the same tires you had when you bought the car. Same with your furnace you need regular maintenance not just filter changes.
I would recommend him on any residential project and for his depth of knowledge a commercial one as well. This guy is passionate about doing a good job well.