Economizer Application/Operation
The energy recovery wheel operation can be altered to take advantage of economizer operation (free cooling). Two modes are available:
1.
2.Modulating the wheel
A field supplied call for cool (Y1) is required.
in the air intake compartment. This primary sensor will
should not light and the energy recovery wheel should energize and rotate.
If these steps provide the results described, the enthalpy economizer is working properly.
•Turn unit power off. Reconnect C7400 Solid State
Enthalpy Sensor to terminal SO.
Modulating the Wheel
In applications in which an internal heat gain is present in the space, the rotational speed of the energy wheel may be modulated (via variable frequency drive) to avoid overheating the space during the winter. The speed of the energy wheel will be controlled in response to the discharge temperature set point.
Sequence of Operation: The variable frequency drive is fully programmed at the factory (refer to VFD section for more information). A “call for cool” must be field wired to the unit (terminals provided in unit - refer to wiring diagram in unit control center) to allow for initiation of economizer mode. When the space calls for cooling, factory supplied controls will drive the following wheel operations:
Testing
Temperature Sensor with Override
•Turn both Temperature and
Override thermostats down as low as they go. The wheel should be rotating.
•Turn the Temperature sensor up as high as it goes, and keep the Override sensor as low as it will go. The wheel should stop rotating.
Temperature
Sensor with
Override
TAO > TRA | Wheel runs at full speed. | |
(maximum energy recovery) | ||
TAO < TRA | Wheel is stopped. | |
and | (no energy recovery) | |
TAO > TSA | ||
| ||
TAO < TRA | Wheel will modulate to maintain | |
and | discharge temperature. | |
TAO < TSA | ||
|
Where (TOA) is the outdoor air temperature set point, (TRA) is the return air temperature set point, and (TSA)
•Turn both sensors as high as they will go. The wheel should start rotating.
•Set the Temperature sensor at desired point for economizer operation to begin. Set the Override sensor at desired point for economizer operation to end (factory default is 65ºF and 50ºF, respectively).
Enthalpy Sensor with Override
•Turn unit power off. Disconnect
C7400 Solid State Enthalpy Sensor from terminal So on the enthalpy controller. Also, disconnect the
620 ohm resistor from
terminal Sr on the enthalpy controller. Turn unit power on. The LED on the enthalpy
controller should light and the energy recovery wheel should not rotate.
•Turn unit power off. Reconnect 620 ohm resistor to terminal Sr on the
enthalpy controller. Turn unit power Enthalpy on. The LED on the enthalpy controller
Controller
12Model ERVe Energy Recovery Unit
is the supply air discharge thermostat set point.