Carrier 40FS - Manual (Page 8)

Treatment.) When electric heater is installed, use
heat resistant material for flexible connector
between ductwork and unit air discharge con­
nection. Ductwork passing thru unconditioned
space must be insulated and covered with vapor
barrier. External ductwork must be insulated and
weatherproofed.
UPFLOW RETURN AIR CONNECTION THRU
THE FLOOR — Size floor opening large enough
to accept flanges on filter section. Make duct flush
with floor. Set unit on floor over opening with
filter section flanges inserted thru floor into duct.
Use fireproof resilient gasket 1/8 to 1/4-in. thick
between duct, unit and floor. For downflow supply
air connection thru the floor, proceed as above,
except size floor opening large enough to accept
flanges on unit air discharge connection. (See
combustible material specifications.)
If a side inlet return air connection is required,
use an accessory return air plenum.
ACCESSORY RETURN AIR PLENUM is avail­
able in 2 sizes for use in upflow installations where
side return air inlet is required. A 21-in. wide model,
40FS900-141, is for use with 40FS160 assemblies,
and a 24-1/2 in. wide model, 40FS900-191, is for
use with 40FS200,220 assemblies and 40FS075
assemblies.
Set 40FS heating and/or cooling assembly in
place on top of plenum. Cut opening in either side
or back of plenum and make return air ductwork
connection. Return air plenums and typical in­
stallation are shown in Fig. 10.
Step 5 — Insulate Ductwork (Thermal and
Acoustical) — Insulate all ductwork passing thru
unconditioned spaces such as hot attics and crawl
spaces. Heat gain due to ductwork transmission
can result in insufficient air supply temperatures at
duct outlets. Metal duct systems that do not have
one 90° elbow and 10 ft of main duct to first
branch takeoff require internal acoustical insula­
tion lining per the following specifications:
Line the inside of plenum, branch runs and
main duct with acoustical insulation in accordance
with the latest edition of SMACNA (Sheet Metal
and Air Conditioning Contractors National Asso­
ciation) application standard for duct liner. Duct
liners should be UL classified batts and blankets
with a fire hazard classification marking of
FHC-25/50 or less. Ensure main duct lining is
extended 6 to 8 ft down the duct from plenum.
As an alternate to above, fibrous glass ductwork
may be used if constructed and installed in
accordance with the latest edition of SMACNA
construction standard on fibrous glass duct.
Both acoustical lining and fibrous ductwork shall
comply with National Fire Protection Association
as tested by UL Standard 181 for Class I air ducts.
RETURN
, AIR
40FS,FQ OR
38HQ HEATER
40FS FAN SECTION
28VQ COIL
AIR CLEANER
40FS ACCESSORY PLENUM
BASEMENT INSTALLATION
Fig. 9 — Heater Spacer Plate Fig. 10 — Accessory Return Air Plenum