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724-746-5500 | blackbox.com
Page 42
724-746-5500 | blackbox.com
Chapter 2: Installation
2.11 Settings and Adjustments
2.11.1 Water–Water/Glycol Circuit
Condensing temperature is maintained by liquid flowing through a regulating valve and then into the condenser. The regulating
valve opens to increase the liquid flow as the refrigerant pressure rises (or closes as the refrigerant pressure falls). The system
controller monitors a signal from a pressure transducer to determine how far to open the valve. The controller automatically
changes the control valve position to maintain head pressure based on the difference between the setpoint value and the actual
measured value. The controller transmits a proportional 0– to 10–VDC signal to the regulating valve with 10 VDC corresponding
to the valve opening 100%.
The system controller is factory set for the correct condensing pressure; however, it can be adjusted to increase or decrease the
pressure. To adjust the pressure, enter the Factory menu in the E2 controller. Contact Black Box Technical Support at
724-746-5500 or info@blackbox.com for a password to enter the Factory menu and for technical assistance if adjustment is
necessary.
Make adjustments in small increments. Allow adequate time between adjustments for the valve to fully respond to the control
signal so you can observe the changes in system operation.
2.11.2 Low-/High-Pressure Limit Switch
Air-conditioning systems using DX refrigerant are equipped with hermetically sealed high-pressure and low-pressure switches.
These switches are pre-set by the manufacturer and cannot be adjusted. The high-pressure switch opens at 630 psig and has a
manual reset. The low-pressure switch opens at 65 psig (± 10) and closes at 105 psig (± 10) and has an automatic reset.
2.11.3 Thermal Expansion Valve
An electronically controlled expansion valve (EEV) maintains constant superheat of the refrigerant vapor at the outlet of the
evaporator by metering the flow of refrigerant into the evaporator. Superheat is the difference between the refrigerant vapor
temperature and its saturation temperature at a given suction pressure. By controlling superheat, the EEV keeps nearly the entire
evaporator surface active while preventing liquid refrigerant from returning to the compressor. As a standard, superheat is factory
set at 12–15° F and should not need adjustment. The superheat temperature is monitored and controlled by the auxiliary control
module (EVD Driver) mounted on the door of the electric box. We recommend that you contact Black Box Technical Support if
adjustment is required.
CAUTION
Do not exceed 20° F superheat. Exceeding this temperature may cause failure of the compressor.
2.11.4 Hot Gas Bypass
A electronic hot gas bypass system is provided for freeze protection and capacity control. The auxiliary control module (EVD
Driver) mounted on the door of the electric box manages operation of the hot gas valve. The hot gas regulator valve allows
refrigerant to flow from the discharge line directly to the evaporator through an auxiliary connection downstream of the thermal
expansion valve. This is used to maintain the evaporator at a minimum constant pressure as the heating load varies.
The hot gas (discharge) regulating valve is set to prevent the surface temperature of the evaporator coil from dropping below
35° F. The bypass temperature is factory set and no adjustment should be necessary. Contact Black Box Technical Support at
724-746-5500 or info@blackbox.com if adjustment is required.
2.11.5 EC Fans
The speed of the EC fans is controlled via a 0– to 10–VDC signal from the system controller. The controller is preset by the
factory for the correct fan speed configuration and should not require adjustment. If the airflow needs to be adjusted, this may be
done using the controller’s programming menu selections. Refer to Section 4.4.4 for instructions on adjusting airflow using the
system controller. Contact Black Box Technical Support at 724-746-5500 or info@blackbox.com when initially making adjustments
to the controller.