Packaged Rooftop Ventilator
20
CAUTION
When operating conditions of the fan are to be
changed (speed, pressure, temperature, etc.), consult
manufacturer to determine if the unit can operate
safely at the new conditions.
Supply Fan (Plenum Type)
The unit contains one plenum supply fan located on
the end of the unit opposite the outdoor air intake and
may optionally have a relief air blower which is referred
to as an exhaust blower in this document. Efficient fan
performance can be maintained by having the correct
offset.
Refer to the respective Installation, Operation and
Maintenance Manual shipped with this unit for additional
start-up and maintenance information regarding the
plenum fan.
Start-Up Components
Fan
The fan should be checked for free rotation. If any
binding occurs, check for concealed damage and
foreign objects in the fan housing.
Inlet
Cone
Wheel
Offset
Offset:
Proper offset, or overlap, is
adjusted by loosening the wheel hub
from the shaft and moving the wheel
to the desired position along the shaft.
The transition between the inlet cone
and the wheel should
be as shown; there is
a smooth feel to the
profile when moving
one component to the
other.
Supply/Exhaust Fan
The optional exhaust fan is a direct-drive plenum type.
Fan speed is controlled by a VFD which, in turn, is
controlled by the microprocessor controller or by an
external signal. Motor speed will be set on the VFD
during the unit Test and Balance, but after that, the
VFD will not normally be changed. Always check the
motor amperage rating shown on the motor nameplate
when changing the fan RPM. All access doors must be
installed except the control center door.
Vibration
Excessive vibration may
be experienced during
initial start-up. Left
unchecked, excessive
vibration can cause a
multitude of problems,
including structural and/or component failure. The most
common sources of vibration are listed.
Many of these conditions can be discovered by careful
observation. Refer to the Troubleshooting section of
this manual for corrective actions. If observation cannot
locate the source of vibration, a qualified technician
using vibration analysis equipment should be consulted.
Generally, fan vibration and noise is transmitted to other
parts of the building by the ductwork. To eliminate this
undesirable effect, the use of flexible connectors is
recommended.
Discharge Air Temperature Sensor
Units are supplied with a Discharge Air Temperature
Sensor that is to be field-installed prior to unit start-
up. The sensor is to be installed at least three duct
diameters downstream of the heat exchanger.
The sensor must be connected directly to the
microprocessor controller. All other sensors and
low voltage devices are to be
connected to the low voltage
terminal strip in the control center.
The discharge air sensor is
shipped loose and can be found
in the unit’s control center. See
the unit-specific wiring diagram
for connection locations.
Optional Hot Gas Bypass Valve
(standard scroll)
To adjust, connect a pressure gauge to the suction line
and block the entering air to the evaporator coil. The
valve should begin to open when the suction pressure
drops to approximately 115 PSIG for R-410A (the valve
will feel warm to the touch). Adjustments are made by
first removing the cap on the bottom of the valve and
then turning the adjusting stem clockwise to increase
the setting pressure (counterclockwise to decrease).
Allow several minutes between adjustments for the
system to stabilize. When adjustment is complete,
replace the cap on the valve.
Vibration Causes
Off axis or loose components
Drive component unbalance
Poor inlet / outlet conditions
Foundation stiffness
Typical Discharge Air
Temperature Sensor
Fan Wheel Rotation Direction
Check for proper wheel rotation by momentarily
energizing the fan. Rotation is determined by viewing
the wheel from the drive side and should match the
rotation decal affixed to the fan housing.
If the wheel is rotating the wrong way, direction can be
reversed by interchanging any two of the three electrical
leads. Check for unusual noise, vibration or overheating
of the bearings. Refer to the Troubleshooting portion of
this manual if a problem develops.
Fan Size
Offset
(inches)
Tolerance
(inches)
ER35C
5/32
± 1/32
ER45C
3/16
± 1/32
ER50C
13/64
± 1/32
ER56C
1/4
± 1/32
