Thanks for the tips. I need to revise the entire system, and I don’t want to hire a professional because they will charge me a lot of money. I think I will be able to do that myself and save some money. OFC, I will see that I cannot finish the work. I will call an HVAC professional, but I want to try at least to do it myself. I know some good professionals from local trade schools and am sure they will do a good job.These schools are all reputable and well-known in their fields . It’s always better to know the guy you will hire personally because this way, you can be sure that he will try his best to complete the job.