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104 RT-PRC031-EN
Mechanical Specifications
Return Air
General
Return air options shall include 100
percent modulating return fan and
100 percent modulating return with
direct space building pressurization
control. Return fans shall be either
standard or low airflow.
100 Percent Modulating Return
Fan
A single width plenum fan with airfoil
blade shall be mounted on a shaft
with fixed sheave drive. The fan shall
be dynamically balanced for the
operating envelop and tested in
factory before being installed in unit.
The plenum fan shall be test run in
unit as part of unit test. Fan operating
envelop rpm shall be below first
critical speed. Fan shaft shall be
mounted on two grease lubricated
ball or roller bearings designed for
200,000-hour average life. Extended
grease lines shall be provided to
allow greasing of bearings from
section base rail. Fan motor and
assembly shall be mounted on
common base to allow consistent
belt tension with no relative motion
between fan and motor shafts. The
entire assembly shall be completely
isolated from unit with 2-inch spring
isolators. Discharge dampers at unit
outlet shall modulate relief airflow in
response to OA / return air damper
position. The return fan VFD shall
operate in conjunction with the
supply fan.
100 Percent Modulating Return
Fan with Statitrac™ Control
Option
A single width plenum fan with airfoil
blade shall be mounted on a shaft
with fixed sheave drive. The fan shall
be dynamically balanced for the
operating envelop and tested in
factory before being installed in unit.
The plenum fan shall be test run as
part of unit final run test. Fan
operating envelop rpm shall be
below first critical speed. Fan shaft
shall be mounted on two grease
lubricated ball or roller bearings
designed for 200,000-hour average
life. Extended grease lines shall be
provided to allow greasing of
bearings from section base rail. Fan
motor and assembly shall be
mounted on common base to allow
consistent belt tension with no
relative motion between fan and
motor shafts. The entire assembly
shall be completely isolated from
unit with 2-inch spring isolators. The
100 percent modulating relief
damper shall be modulated in
response to building pressure. A
differential pressure control system,
(Statitrac), shall use a differential
pressure transducer to compare
indoor building pressure to outdoor
ambient atmospheric pressure. The
(Statitrac) control system shall
modulate the discharge dampers to
control the building pressure to
within the adjustable, specified
deadband that shall be adjustable at
the Human Interface Panel. The
return fan VFD shall modulate in
response to return duct static
pressure.
Fresh Air
General
Three outside air options: 0 to 25
percent motorized controlled outside
air, 0-100 percent fully modulating
economizer, and 0-100 percent fully
modulating economizer with fresh air
measurement.
Demand Control Ventilation
The fresh air damper position shall
modulate in response to a CO
2
sensor in the conditioned space, in
order to minimize the unit energy
consumption, yet simultaneously
meet the ventilation requirements of
ASHRAE Std 62.1.
Fresh Air Measurement
A factory mounted airflow
measurement station (TRAQ) shall be
provided in the fresh air opening to
measure airflow. The airflow
measurement station shall measure
from 15 to 100 percent of unit airflow.
The airflow measurement station
shall adjust for temperature
variations.
0-25 Percent Motorized Outside
Air Damper Option
0-25 percent motorized outside air
damper shall provide up to 25
percent outside air. The damper
position will be adjustable at the
Human Interface Panel.
0-100 Percent Modulating
Economizer Option
Operated through the primary
temperature controls to
automatically utilize OA for “free”
cooling. Automatically modulated
return and OA dampers shall
maintain proper temperature in the
conditioned space. Economizer shall
be equipped with an automatic
lockout when the outdoor high
ambient temperature is too high for
proper cooling. Minimum position
control shall be standard and
adjustable at the Human Interface
Panel or with a remote potentiometer
or through the building management
system. A spring return motor shall
ensure closure of OA dampers during
unit shutdown or power interruption.
Mechanical cooling shall be available
to aid the economizer mode at any
ambient. Standard economizer
dampers shall have a leakage rate of
20 cfm/ft^2 at 1.0 in W.C. pressure
difference.
Low Leak and Ultra Low Leak
Economizer Dampers Option
Low leak dampers shall be provided
with chlorinated polyvinyl chloride
gasketing added to the damper
blades and rolled stainless steel jamb
seals to the sides of the damper
assembly. The low leak dampers
shall have a leakage rate of 10 cfm/
ft^2 (AMCA Class 2) at 1.0 in W.C.
pressure difference.
Ultra low leak damper will have
added sealing under the jam seals
and in the frame. The ultra low leak
dampers shall have a leakage rate of
4 cfm/ft^2 (AMCA Class 1) at 1.0 in
W.C. pressure difference.
Note: Based on testing completed
in accordance with AMCA
Standard 500D.