036-21540-001-A-0503
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Unitary Products Group
OUTDOOR AIR DUCTWORK
When installing ductwork, adhere to local Codes and
sensible practice. Minimize duct runs and avoid abrupt
changes in direction where possible. Allow ample
access space for servicing of the coils and changing of
filters. Perform regular maintenance on ducts to
increase unit life, maintain efficient operation, and
reduce accumulation of explosive dust. Refer to blower
performance charts, and engineer duct runs and
accessory pressure drop so as not to exceed maximum
external static values.
LOUVER SIZING GUIDELINES
One of the key issues in obtaining optimum perfor-
mance from indoor air-conditioners is the proper selec-
tion of the condenser intake and discharge louvers.
Unlike outdoor air cooled units, which intake and dis-
charge their cooling virtually unrestricted, indoor units
must overcome the resistance of grilles or louvers at
the outside wall - plus the restriction of any intercon-
necting ductwork.
Our indoor air cooled air-conditioners are designed to
accommodate the external static pressure loss associ-
ated with properly sized louvers of the "storm proof”
type. This type of louver typically has a free area
approximately 40-45% of the actual louver size. To
determine the free area required for any given unit,
adhere to the following guidelines:
•
Size condenser air intakes for 500-750 feet/minute
nominal velocity (Maximum recommended 800
feet/minute)
•
Size condenser air discharge for 1,200-1,500 feet/
minute nominal velocity (Maximum recommended
1,700 feet/minute)
The use of louvers with higher velocities than above
may be employed, at the discretion of the engineer/
installer, provided that the total air pressure drop does
not exceed the capability of the condenser fan and
motor. The use of low restriction louvers with shallow
blade angles can allow higher face velocities without
excessive static pressure loss.
Exceeding the static pressure capability of the con-
denser fan will result in insufficient condenser air vol-
ume. This will cause a loss in system capacity, and
may cause compressor shutdown during high ambient
periods. (Installation of an oversize condenser motor/
drive, where applicable, may be considered in such
cases.)
(As a general rule, these velocities will require an
intake louver sized approximately 1.25 to 1.5 times the
dimensions of the duct connection on the unit, and a
discharge louver sized approximately 1.5 to 2 times the
duct connection dimensions.)
Use only louver sections that provide different deflec-
tion angles for air discharge and air intake, to ensure
the unit does not short circuit. Protect the unit from
weather conditions (rain, snow) entering through the
condenser air intake. All outdoor air ducts should pitch
away from the unit, toward the outside wall. Connect all
ducts to unit with canvas section duct connectors or
choose another suitable noise and vibration absorbing
device.
NOTE:
The Manufacturer will not accept any liability result-
ing from incorrect installation of this equipment. Fol-
low installation instructions carefully.
