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724-746-5500 | blackbox.com
Page 58
724-746-5500 | blackbox.com
Chapter 4: E2 Controller
4.4.3.2 Water–W/G Operation
When the system is turned on, the controller activates the fluid supply control valve with a proportional/integral (P/I), 0–10 VDC
signal. The valve opens proportionally based on head pressure. The control parameters are adjustable in the Factory menu. If
adjustment is required, contact Black Box Technical Support at 724-746-5500 or info@blackbox.com.
The control valve changes position to adjust coolant flow to keep the head pressure to the control setpoint and maintain it. If the
head pressure rises, the valve position continues to modulate open as needed, up to 100% (fully open), to maintain the control
setpoint.
The control output signal is matched to the valve. If the valve typically opens at 2.5 VDC, the control I/O module will generate the
appropriate voltage for opening the valve starting at the minimum voltage of 2.5 VDC. From there the signal increases as needed
until the valve position reaches 100% open.
4.4.3.3 Dehumidifying
When dehumidification is called for, the blower speed automatically changes to the dehumidification fan speed setting. The
controller will operate the system in the cooling mode at full output to strip moisture from the air. The system will remain in the
cooling mode until the actual relative humidity (or dewpoint) reaches the control setpoint plus the dehumidification cut-out offset.
If the control temperature drops below the low temperature cutout setpoint for the dehumidification mode (temperature setpoint
minus 4° F default), cooling operations will stop.
4.4.4 Airflow/Fan Speed Control
The E2 controller treats each EC fan as a variable speed fan. The controller manages the speed of each fan from a factory-set
minimum up to a factory-set maximum speed. The minimum fan speed is used whenever the A/C unit has no cooling operations
running. The maximum fan speed setting is used during times when the A/C unit is cooling. A dehumidification fan speed setting
is used when the system is in the dehumidification mode. The speed settings are adjustable in the Service>Blower>Blower Set Up
menu loop (see Section 4.5.5.4).
EC fan speed is automatically varied based on temperature. There are mechanisms to trade off the control valve opening versus
fan speed. When the system enters the dehumidification mode, the fan speed automatically changes to the dehumidification
speed setting.
The E2 controller's software is equipped with an operational fail-safe mode. Upon sensing a temperature sensor failure, the
controller signals an alarm. It continues to develop the fan control outputs by calculating the averaged value of the remaining
sensors to replace the input value of the failed sensor. If all the temperature sensors fail, the controller develops the control
outputs based on the entered temperature setpoint value minus a 3° F temperature offset. This allows the Cold Row system to
continue operating while the cause of the problem is corrected.
The controller continually monitors fan operation. Cold Row DX units are equipped with a pneumatic air proving system connect-
ed to a flow switch that detects the loss of airflow when a fan fails to operate.
If one of the fans fails to operate, the controller alerts the operator with an alarm message and increases the speed of the
remaining two fans to 99.9% to compensate for the loss of airflow. If the fault does not clear, the fans shut down for 5 seconds
and then restart. If the fault continues, the fans reset a second time. If the fault does not clear after the second reset, the fan(s)
that generated the fault are shut down and the remaining fans continue operation at 99.9% speed.
If the BMS monitoring/control signal fails, the E2 controller will default to local operation at the current setpoints for the fans. The
local sensors have priority over the BMS system.