I own a condo. Their heating and cooling is central and each condo has something that blows out hot/cold air. I guess something like what they have in a hotel. Last summer it wasn’t cooling properly and repairs didn’t last long. Does this mean it it’s time to replace it? How do you interface it to the main system in the building. The building is about 50 years old and the cooling heating system is original. Heating work but not cooling.