I've had to replace several heat exchangers since installing a new unit in 2002. My 1938 home is 1450 sf and located in middle GA. The unit is a 3 ton/100,000 btu Goodman gas pack.

After the second heat exchanger cracked, the installer and I squeezed larger 16 inch flex into the crawlspace opening and added a bigger 14 inch return boot. To keep from having two 90 degree supply and return lines out of the unit, we moved it away from the house for a gentler slope to the below grade crawlspace. I never liked the setup because my unit is so large and altogether sits seven feet away from the house.

A new company confirms my suspicions that we're still starving the unit for air causing the exchanger failures. They want to keep the squeezed flex and use metal duct soon afterwards, put a 45 degree elbow to make a smoother transition, and add a bigger 16 inch return. For an extra amount they can add another 20x25 return by sacrificing closet space.

Is the 100,000 btu unit way too much for my house? Do I have other duct or unit options? Is it a bad idea to dig the area out to lower the unit below grade (concrete well) so I can have the unit closer to the house without a transition down to match the crawlspace? I could put a sump pump in the well to pump water out that might collect there during a rain. The last 2.5 ton unit was replaced for a cracked heat exchanger too but it was built in 1985. Thanks for any information and sorry for the wordiness here.