I would greatly appreciate any advice from the forum on this. I bought a 2,800 sq ft house that was gutted, remodeled, and had an addition that doubled the house size (single story ranch). All new sheet rock, ceilings, insulation, windows, siding, plumbing, electrical, roof, and HVAC system. The builder used an HVAC contractor that never did a Manual J calc, and installed two 3-ton Goodman 16 Seer heat pump split systems with the condensers right next to the master bedroom window. I've been in the house for four months, now in middle of the hot South Carolina summer. I hired a third party, qualified HVAC contractor to give me a detailed report of the many installation deficiencies (too ugly and numerous to list) and he told me that the system is way oversized for the house.
I bought HVAC-Calc and ran the Manual J calcs myself with great care. As an engineer and competent software user, I am confident that the software is giving me accurate results. Using this, HVAC-Calc specifies a 2.5 ton system for the Living Space zone, and a 1.5 ton system for the Bedroom zone (with conservative inputs for the infiltration, insulation, shading, windows, etc). The contractor installed a 3 ton system for the Living Space zone and another 3 ton system for the Bedroom zone. The BR zone system is double what it needs to be.
I'm aware of the problems with having an oversized system, but the sad fact is that it is so common for HVAC contractors to oversize systems - how much of a case do I need to show negligence in order to force my builder to correct the problem and replace the system with the right sized units? When I told my builder and another Goodman contractor about the problems their first response was "it should be the right size units according to your home's square footage and using a rule of 1 ton per 500 sq ft."
I would appreciate any helpful advice. Thanks in advance!