If anyone finds this reference

Housed Plenum Array , Plug and Plenum Fans - Greenheck

www.greenheck.com/media/pdf/.../475405HPA-Plug-Plenum_iom.pdf

Feb 1, 2001 - Plenum (QEM, QEP). Only qualified personnel should install this fan. Personnel should have a clear understanding of these instructions and should be aware of ...

Please be aware the 2001 date is a Google dating problem, Greenheck does not start producing this system till post 2010.

I verified the post 2010 with the company to confirm it was a Google dating problem.