first of all, i'm sorry! (i hate arcoaire with a passion!!) we have one at our house and i must say, it is a piece of crap! you better watch those wires on the condenser fan motor. THEY WILL FALL DOWN INTO THE UNIT AND STALL THE MOTOR!!
so anyways, you had a question about BTU's. the compressor name plate does not really indicate capacity. my best idea would be to call WINAIRE. they are a supply house that deals with arcoaire. they should be able to help.