Carrier 50CR - Manual (Page 9)

9
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,
Refrigeration, and Air Conditioning Engineers) recommendations.
The unit has duct flanges on the supply-- and return--air openings on
the side of the unit.
ELECTRICAL OPERATION HAZARD
Failure to follow this warning could result in personal injury
or death.
For vertical supply and return units, tools or parts could drop
into ductwork, therefore, 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.
! WARNING
When designing and installing ductwork, consider the following:
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 max cooling air quantity (400 cfm/ton).
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) minimum 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 installing or servicing system, always turn off main
power to system. There may be more than one disconnect
switch.Turn off accessory heater power switch if applicable.
! WARNING
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
knockouts.
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.
4. Ensure the side duct covers are in place to block off the
horizontal air openings (See Fig. 11).
Step 6—Provide for Condensate Disposal
NOTE: Ensure that condensate--water disposal methods comply
with local codes, restrictions, and practices.
The units dispose of condensate through a 3/4 in. NPT female fitting
that exits on the compressor end of the unit. Condensate water can
be drained directly onto the roof in rooftop installations (where
permitted) or onto a gravel apron in ground level installations.
Install a field--supplied condensate trap at end of condensate
connection to ensure proper drainage. Make sure that the outlet of
the trap is at least 1 in. lower than the drain--pan condensate
connection to prevent the pan from overflowing. Prime the trap with
water. When using a gravel apron, make sure it slopes away from the
unit.
If the installation requires draining the condensate water away from
the unit, install a field--supplied 2--in. trap at the condensate
connection to ensure proper drainage. Condensate trap is available
as an accessory or is field--supplied. Make sure that the outlet of the
trap is at least 1 in. lower than the unit drain--pan condensate
connection to prevent the pan from overflowing. Connect a drain
trough using a minimum of field--supplied 3/4 --in. PVC or
field--supplied 3/4 --in. copper pipe at outlet end of the 2 --in. trap
(See Fig. 12). Do not undersize the tube. Pitch the drain trough
downward at a slope of at least 1 in. for every 10 ft. of horizontal run.
Be sure to check the drain trough for leaks. Prime the trap at the
beginning of the cooling season start--up.
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