OK,my friends house is like 1,700 sq.ft. and the current system is a 30,000 btu/hr Ducane split system installed in 1999,the model number is:HP12B30.paired with a Lennox air handler in the closet.

Thanks,

Mike

This question can`t be answered without someone first looking over the home and doing a manual J calculation,, to determine the exact size needed