Kit Assembly and Installation Manual 2.0

Step 7: Attach duct takeoffs according to the table below. Insert the tabbed end of the takeoff
into the plenum and bend the tabs to make a secure fit. Finish with tape and mastic for an
airtight seal.
Air handler model
Recommendation for # of takeoffs and diameter takeoffs
BM12MCD
3 six inch ducts, or 2 seven inch ducts for the supply and a minimum return of a 10
inch duct and a preferred return of a 12 inch duct
BM18MCD
4 or 5 six inch ducts, 3 seven inch ducts, or 2 eight inch ducts for the supply and a
minimum return of a 12 inch duct and a preferred return of a 14 inch duct
BM24MCD
7 six inch ducts, 4 seven inch ducts, or 3 eight inch ducts and a minimum return of a
14 inch duct and a preferred return of a 16 in duct
BM36MCD
5 eight inch ducts, or 6 seven inch ducts and a minimum return of a 16 inch duct and
a preferred return of an 18 inch duct.
Step 8: Attach the Supply plenum to the concealed duct, fitting around the flange. Attach with
S Cleats and seal with mastic. Put one S-Cleat on top of the plenum, above the flange, and you'll
screw 3 screws into that flange through it. 1 at each end, 1 in the middle. Just tight enough to
provide some tension by that cleat on top of the plenum down to the flange and you can repeat
on the bottom side. Option - use sheetmetal screws into the flange for a more secure
attachment. Still use mastic for air sealing.
Step 9: Attach the Return plenum by butting it up to the return opening. There are no flanges
on the return side, but the Return plenum is the same size as the unit chassis, and can be
taped on directly. We recommend that you remove the filter screen and reattach further
upstream in a location you can access for maintenance, such as the return register.
Note: Ductboard is subject to minor tears and dents in shipping, or while being worked. These
can easily be patched with foil tape. A good, airtight plenum is the most important
consideration.