Step 5—Select and Install Ductwork
The design and installation of the duct system must be in
accordance with the standards of the NFPA for installation of
non-residence type air conditioning and ventilating systems, NFPA
90A or residence type, NFPA 90B and/or local codes and
ordinances.
Select and size ductwork, supply-air registers, and return air grilles
according to ASHRAE (American Society of Heating, Refrigera-
tion, and Air Conditioning Engineers) recommendations.
The unit has duct flanges on the supply- and return-air openings on
the side of the unit.
When designing and installing ductwork, consider the following:
For vertical supply and return units, tools or parts could drop
into ductwork and cause serious injury or death. Install a 90
degree turn in the return ductwork between the unit and the
conditioned space. If a 90 degree elbow cannot be installed,
then a grille of sufficient strength and density should be
installed to prevent objects from falling into the conditioned
space. Units with electric heaters require 90 degree elbow in
supply duct.
1. All units should have field-supplied filters or accessory filter
rack installed in the return-air side of the unit. Recommended
sizes for filters are shown in Table 1.
2. Avoid abrupt duct size increases and reductions. Abrupt
change in duct size adversely affects air performance.
IMPORTANT: Use flexible connectors between ductwork and
unit to prevent transmission of vibration. Use suitable gaskets to
ensure weather tight and airtight seal. When electric heat is
installed, use fireproof canvas (or similar heat resistant material)
connector between ductwork and unit discharge connection. If
flexible duct is used, insert a sheet metal sleeve inside duct. Heat
resistant duct connector (or sheet metal sleeve) must extend 24-in.
from electric heater element.
3. Size ductwork for cooling air quantity (cfm). The minimum
air quantity for proper electric heater operation is listed in
Table 2. Heater limit switches may trip at air quantities below
those recommended.
4. Seal, insulate, and weatherproof all external ductwork. Seal,
insulate and cover with a vapor barrier all ductwork passing
through conditioned spaces. Follow latest Sheet Metal and Air
Conditioning Contractors National Association (SMACNA)
and Air Conditioning Contractors Association (ACCA) mini-
mum installation standards for residential heating and air
conditioning systems.
5. Secure all ducts to building structure. Flash, weatherproof, and
vibration-isolate duct openings in wall or roof according to
good construction practices.
CONVERTING HORIZONTAL DISCHARGE UNITS TO
DOWNFLOW (VERTICAL) DISCHARGE UNITS
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury
or death.
Before performing service or maintenance operations on
system, turn off main power to unit and install lockout tag.
Turn off accessory heater power switch if applicable.
1. Open all electrical disconnects and install lockout tag before
starting any service work.
2. Remove side duct covers to access bottom return and supply
knock outs.
NOTE: These panels are held in place with tabs similar to an
electrical knockout.
3. Use a screwdriver and hammer to remove the panels in the
bottom of the composite unit base.
Fig. 4—Corner Weights (in Pounds)
CORNER #
50SD
024 030 036 042 048 060
1 69 74 87 93 97 99
2 53 57 68 72 74 76
3 83 88 104 111 116 119
4 138 147 174 184 193 198
TOTAL WEIGHT 343 366 433 460 480 492
C00071
12
43
x
y
5
To Next Page
Loading...
