Originally Posted by
SiriusDG
Thanx Teddy Bear.
The original system was 3 and the house was never less then 80 in the summer, we made the jump hoping to at least be comfortable. We got no warning of the dangers of doing so. The guys who came out the other day told us the ducting was sized for 2 or 2.5, so it appears someone else already upsized before we purchased, and we upsized their upsize, just compounding the problem.
Your OP stated the original size was 2.5; here you stated 3, so pardon my confusion.
Regardless, you got bad advice from whomever suggested an increase in tonnage was required with NO investigation into other potential causes for the existing system to perform below capacity. The harsh truth is most installed residential systems never perform close to design capacity due to poor duct installation and other improper installation practices, in addition to entrenched stupid design decisions like running ducts through an attic that gets super hot in summer. If you live in a primarily cooling climate and have no choice but to run ducts in the attic (due to lack of a basement or crawl space) then the best decision YOU can make as a homeowner is to make the attic cooler year round, along with properly sized, sealed, and installed ductwork. Approaches to cooler attics run from "cool roof" to radiant barriers to spraying foam insulation on the roof deck. The only radiant barrier that impress me are the ones glued to roof decking, so that leaves out most existing homes unless the decking is replaced during a reroof. "Cool roof" approaches are varied and not necessarily all that much more expensive than perpetuating the problem by replacing heat soaking old asphalt with heat soaking new asphalt shingles. Foaming the roof deck and sealing the attic is the most costly but will also accomplish making your house far more comfortable year round.
Of course, if you're not interested in getting your ductwork corrected to proper size and layout, I'm not sure you'd be interested in "building performance remodeling" tips, either, but these posts are read by many and someone may get a good head full of wisdom and find out first hand how smart it really is to focus on the building AND the HVAC as a holistic approach to human comfort.
Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.