The document discusses a Manual J calculation for HVAC equipment sizing. It recommends following the numbers from the Procalc software, as the vendor's calculations were likely incorrect by undersizing the equipment. It has never heard of a case where a Manual J calculation determined equipment was too large. It also notes Manual J does not account for internal loads or time-dependent heat transfer aspects. It suggests variable speed mini split systems are cost effective for most equipment in that size range if installation is being paid for.

1. Comment on Manual J slop? by MattJF
Go with the Procalc numbers, your PS points out pretty much exactly what is wrong with the
vendors numbers. I don't think I have ever heard of a manual J being done and it later being
determined the equipment was undersized. I would be interested if there have been any such cases.
At least on the heating side, manual J does not factor in any internal load contributions or account
for any thermal capacity and time dependent aspects of heat transfer.What are you looking at for
equipment? In those sizes variable speed mini split systems are cost effective with just about
anything I am aware of at this time if you are paying for installation.