Carrier COBRA 48/50HJ004-014 - Manual (Page 3)

3
If electric control power or gas service is to be routed
through the basepan, a field-installed accessory thru-the-
bottom connection must be used. Attach the accessory to the
basepan per the information in the accessory installation
instructions. Thru-the-bottom connections must be installed
before unit is set on roof.
If the combined unit roof curb is not being used, additional
support may be desired under the energy recovery section of
the unit. An accessory support and pad for the energy recovery
section can be used. See Fig. 4. Place the protective rubber pad
on the roof so that the edge near the unit is located about 6-in.
from the end of the energy recovery section. Measure the
distance from the bottom of energy recovery rails to the pad.
Adjust the energy recovery equipment support to match the
measured distance and screw into place with the 4 screws pro-
vided. See Fig. 4. Place the support underneath the energy re-
covery unit and on the protective rubber pad. This is done by
lifting the end of the energy recovery section slightly above
level and then sliding the support underneath the rails.
Curb should be level. This is necessary for unit condensate
drain to function properly. Refer to Accessory Roof Curb
Installation Instructions for additional information as required.
Step 3 — Field Fabricate Ductwork — Secure all
ducts to roof curb and building structure. Do not connect duct-
work to unit. Insulate and weatherproof all external ductwork,
joints, and roof openings with counter flashing and mastic in
accordance with applicable codes. See Fig. 5A and 5B for duct
dimensions.
Ducts passing through an unconditioned space must be
insulated and covered with a vapor barrier. If a plenum return is
used, the return should be ducted through the roof deck to com-
ply with applicable fire codes.
A minimum clearance is not required around ductwork.
These units are designed for a minimum continuous heating
return-air temperature of 50 F (dry bulb), or an intermittent
operation down to 45 F (dry bulb), such as when used with a
night set-back thermostat. To operate at lower return-air
temperatures, a field-supplied outdoor-air temperature control
must be used to initiate both stages of heat when the tempera-
ture is below 45 F. Indoor comfort may be compromised when
these lower air temperatures are used with insufficient heating
temperature rise.
IMPORTANT: The gasketing of the unit to the roof curb is
critical for a watertight seal. Install gasket supplied with the
roof curb as shown in Fig. 3A and 3B. Improperly applied
gasket can result in air leaks and poor unit performance.
Deck pans
78 1/4"
49 15/16"
14"
110 11/16"
49 15/16"
14"
Deck pans
Supply
SIDE VIEW
END VIEW
2"
R 1
2" Return support.
Only used on some
applications.
DUCT OPENING SIZES
Supply = 15 11/16" x 31 3/8"
R1 = 15 5/16" x 29 1/16"
R2 = 15 5/16" x 9"
R1 = Return from building to HVAC
R2 = Return from building to 62AQ
R 2
3 1/4
Fig. 2B — COBRA™ Energy Recovery Unit Full-Perimeter Roof Curb — 48/50HJ008-014 with 62AQ200,300