Operating Configurations; Cw Cooling; Humidifying; Dehumidifying - Black Box CRCW-12 User Manual

Cold row chilled water (cw)

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Chapter 4: E2 Controller

Figure 4-19. Dewpoint control.

4.4.3 Operating Configurations

The operating configuration for the controller depends on what type of air conditioner is being controlled (that is, AR, CW, W/G)

and what features are selected. The operating configuration is preset by the factory according to the application. If certain

features discussed in this manual are not factory enabled, no screens for that feature will appear in the controller user interface

display.

Upon a call for cooling, the controller activates a chilled water control valve with a proportional/integral (P/I), 0-10 VDC signal.

The valve opens proportionally to the demand for cooling based on air temperature. The control settings include a setpoint and a

control dead band. The cooling band is adjustable from 0–10° F in the Factory menu. Contact Black Box Technical Support

at 724-746-5500 or info@blackbox.com for guidance if adjustment is needed.

When the control air temperature exceeds the programmed setpoint plus offset, the CW valve opens, allowing CW to flow to

return the air temperature to the setpoint and maintain it. If the control air temperature continues to rise, the chilled water valve

position continues to modulate open as needed, up to 100% (fully open), to maintain the temperature setpoint.

The control output 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.

If this option is selected (available on CRCW-24 units only), an on-board steam humidifier may be turned on or off by the

controller to maintain relative humidity to a control setpoint. Once the controller enables humidification, the humidifier will

operate at 100% capacity until the humidity setpoint is reached. An on-board control module manages the humidifier operation,

i.e., humidity production, fill cycles, and drain cycles.

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. In a CW system, the control

valve may be set to be less than 100% open for dehumidification if desired in the Service>Humidity menu (see Section 4.5.5.2).

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.

724-746-5500 | blackbox.com

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Crcw-24