Supply Air (Sa) Ductwork; Horizontal Supply Air; Top Discharge Supply Air; Figure 15 - Supply Grille With Volume Damper And 1/8-Inch Neoprene Tape Applied To Perimeter - Johnson Controls VB09 Installation, Operation And Maintenance Manual

SECTION 1 - INSTALLATION

SUPPLY AIR (SA) DUCTWORK

Ensure there is no direct contact between
cabinet sheet metal parts and drywall en-
closure. This includes RA and SA flanges.
Failure to follow these instructions will
negatively affect unit sound performance.

Horizontal Supply Air

A 2-inch duct flange (field provided) may be required
to eliminate supply air recirculation when shallow pro-
file, single deflection supply grilles are installed at the
cabinet discharge openings. If the discharge from the
cabinet is not ducted completely into the conditioned
space, air can recirculate into the RA opening from the
space inside the drywall enclosure.
Manufacturer supplied grilles have a clearance of a 1/4
inch around the perimeter to fit inside the unit supply
flange. Other grille manufacturers could have different
clearances that should be verified.
Field supplied gasket must be applied in order to pre-
vent air recirculation and vibration transfer when sup-
ply grilles are mounted to unit supply opening. When
mounting supply grilles with optional volume damper
directly to cabinet supply flange, the volume damper
fits inside the cabinet supply flange. It is recommended
to apply 1/8-inch neoprene tape (field supplied) around
the perimeter of the volume damper prior to inserting
it into the supply opening. See Figure 15 on page 24
for an example. This assists in reducing noise transmis-
sion and air recirculation into the unit closet.
For ducted openings, connect the unit supply opening
to the supply ductwork using a watertight flexible duct
connector. This minimizes the transmission of operat-
ing sounds through the supply ductwork. Elbows with
turning vanes or splitters are recommended to mini-
mize air noise due to turbulence and to help reduce
static pressure.
24

Top Discharge Supply Air

Units that are installed with a top discharge should be
connected to the supply ductwork with a watertight
flexible connector. This minimizes the transmission
of operating sounds through the supply ductwork. El-
bows with turning vanes or splitters are recommended
to minimize air noise due to turbulence and to help re-
duce static pressure.
For information on available unit horizontal and top
supply openings see Table 5 and Table 6 on page 26.
Recommended face velocity at the outlet supply grille
is 300–500 FPM. Table 6 gives face velocity at the unit
supply openings in relation to Table 5. To calculate the
face velocity at the supply grille, take the FPM from
Table 6 and divide by the supply grille area factor.
FIGURE 15 - SUPPLY GRILLE WITH VOLUME
DAMPER AND 1/8-INCH NEOPRENE TAPE
APPLIED TO PERIMETER
FORM 145.18-IOM1
ISSUE DATE: 8/30/2018
LD27622