I have been using Carrier HAP for close to a year and just finished up a 3 day training course in Trace. I like both programs but HAP is limited in the number of system types it can model. As far as I know HAP cannot model ground loops, Trace can. The newest release (out in Dec I think) of...
The research experts I've spoken to recommend a minimum U-tube velocity of 2.5fps. That has become our office standard. If you plan to vary your loop flow (which I would recommend from an energy perspective) I would select a design point between 3.5 and 5fps as GMcD has suggested to ensure...