Chapter 2: Installation
2.11Settings 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
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
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
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
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
2.11.5 EC Fans
The speed of the EC fans is controlled via a 0– to
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