Very new to HVAC talk . Can you install a 4 ton indoor air handler within the room of the main church but not above a ceiling and can you have an open return with no ductwork on the return side ? As well do you have to install smoke detector? The building is an older office building and is going to be church. It has no fire system installed. The ceiling is 14 high and the floor this unit is serving is about 1200 square feet and has to also cool a mens and ladies room with three stalls each.