Fan Rpm; Fan Wheel; Motors; Setting For Options - Greenheck ERV-251 Installation, Operation And Maintenance Manual

4. Check Blower Rotation
First, hand rotate the blower to ensure that the wheel is not rubbing against the
scroll. If the blower is rotating in the wrong direction, the unit will move some air
but not perform properly.
To check the rotation, open the blower access panels, which are labeled either
supply or exhaust, and run the blower momentarily to determine the
rotation.
To reverse the rotation, turn the power off and use the following procedure:
• For single phase units, rewire the motor per the instructions on the motor.
• For three phase units, interchange any two power leads.
This can be done at the motor starter.
5. Air Volume Check and Measurement
Along with the building balance, the units air volume (cfm) should be measured and
compared with its rated air volume. This unit is flexible (fixed drives for 15 hp units)
for varying air volume, but the actual air volume should be known for making final adjustments.
Note: Model ERV-251 is direct drive, balancing damper or speed control needed for air flow balancing.
The most accurate way to measure the air volume is by using the pitot traverse method in the ductwork away
from the blower. Other methods can be used but should be proven and accurate.
To adjust the air volume, change the fan rpm or the system losses. See Trouble Shooting section on page 20.
6. Measure Motor Voltage, Amperage and Fan RPM
All access doors must be installed except the control center door (Exception: ERV-522 control center door
must be installed). Measure and record the input voltage and motor amperage(s).
To measure the fan rpm, the blower door will need to be removed. Minimize measurement time because the
motor may overamp with the door removed. Do not operate units with access doors/panels open as the
motors will overload.
With blower door closed compare measured amps to the motor nameplate full load amps and correct if
overamping.
7. Settings for Optional Components
Frost Control
Preheater: If outdoor air temperature is below set point then the preheater heats incoming outdoor air above
the Frost Threshold temperature. Typical settings are shown at the right.
Timed Exhaust: De-energizes the outdoor air blower for a
specified period, if the outdoor temperature is below the set
point. The outdoor air blower returns to normal operation for a
specified period. This cycle ends when the outside
temperature rises above the set point.
Typical settings are: Temp. Sensor : 0°F,
Timer (Blower Off): 5 minutes and Timer (Blower On) 45 minutes.
Outdoor/Economizer Sensors
All economizer sensors must be by-passed for proper winter or heating season operation. The by-pass can
be accomplished utilizing the Auto-override option or by wiring a summer/winter switch as shown on the ERV
wiring or ladder diagram.
Temperature Sensor: De-energizes the energy wheel drive motor when the outdoor temperature is below
the set point. The wheel motor re-energizes when the outdoor air temperature is above the set point.
Typical settings are: 65°F
Enthalpy Sensor: De-energizes the energy wheel drive motor when the outdoor enthalpy drops below the
set point. The wheel motor re-energizes when the outdoor air enthalpy is above the set point.
Four settings available on controller.
FROST THRESHOLD TEMPERATURE
Indoor RH at
70° F
20%
30%
40%
Airflow
Frost Threshold
Temperature
-10°F
-5°F
0°F
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