Gas and Oil Home Heating Furnaces - air conditioning

I have a 1250 square ft office with a 3500 btu furnace/airconditioner unit. My office temperature goes up everyday whether we are open or not. When set at about 72, it goes up to 76-78. Workman just put in air return vents saying that would help hot air get out, but there is no change. Now he says it's possibly the evaporater which could be blocked. This has been going on for years with two different a/c men telling me they can't figure it out change the problem without me spending thousands of dollars. My office is a free standing house, brick with storm windows and good insulation. I do have office machines running in one room. Please help

A dirty or blocked cooling coil is an easy diagnosis and any qualified a/c tech should be able to figure it out. It sounds like this is a long standing problem that may in fact be an inadequate design. A good heating/cooling system requires not only proper sizing but also getting the right amount of air into each space via adequate ducting. My suggestion is for you to go back to square one and perform a heating/cooling load calculation. You can do this yourself. It's not that hard and who knows your building better than you do? Go to www.hvaccomputer.com where, for $39, you can download a one time version of a professional calculation procedure that a/c contractors use. It's based on the industry standard Manual J. You might have to call the manufacturers of the office machines to get some heat rejection numbers from them. Another consideration- indoor design temperature for cooling is normally 75 degrees. If you need 72 degrees, be sure to plug that number into the program. BTW- In your post, I think the size of your existing unit is missing a zero. You probably have a 35000 btu system which would be 3 tons.

Thanks big John. I did send for the hvac program.:)