What is the rule of thumb for the number for return grilles?
Commercial office building with the return via a dropped ceiling plenum. It has a separate perimeter heating/cooling system (diffusers above windows) and central ventilation/cooling system with VAV boxes and diffusers. Building maintenance can install new grilles; it is just changing a ceiling tile.
The question is, rule of thumb, how many return grilles per diffuser should a room have? Clearly at least one (there are some rooms with zero and tenants call them iceboxes). But in a room with 4 diffusers? Or in an interior room with no heating vs. an exterior room with heating?
First Rule of Thumb;
Originally Posted by DavidNJ
There are no rules of thumb.
CFM in CFM out
Yup. Also depends on type, perforated will move a much lower volume than egg crate. Leaking boxes and morning warm up schemes matter a bunch too. You could easily do all the wrong things for all the right reasons.
Originally Posted by second opinion
The building owner would probably prefer it be left to a qualified service outfit rather than a building maintenance guy.