03-14-2012, 12:30 AM
The furnace is probably oversized given that rate of heat increase. It is very common for fly by night HVAC contractors to oversize a furnace and not bother with the proper sizing calcs. It doesn't cost them anything and it ensures that they won't get call backs from cold customers. It also results in annoying short furnace cycles which will eventually kill the furnace.
Either the AC is undersized (or is broken...i.e. freon leak, etc) or you have an excessive heat gain problem, which could result from excessive south exposure windows with no low-e coating, lack of insulation, or too many heat sources (incandescent lamps, stove with pilot, etc) inside.
Either the AC is undersized (or is broken...i.e. freon leak, etc) or you have an excessive heat gain problem, which could result from excessive south exposure windows with no low-e coating, lack of insulation, or too many heat sources (incandescent lamps, stove with pilot, etc) inside.