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The common wires on all switches are connected together. All switches are closed unless a fault condition is detected. All safety and protective devices must be installed and used in accordance with applicable codes and regulations. Switches All switch connections are wired to terminal strips in a junction box on the Compressor Module. Switch Status • Low Inlet Gas Pressure Normally Open, closes on pressure rise • High Discharge Gas Pressure Normally Closed, opens on pressure rise • High Temperature Normally Closed, opens on temperature rise Electrical Considerations - Variable Speed Compressor Module • The Compressor power for a variable speed Compressor Module is the Variable Frequency Drive (VFD). • Compressor speed control can be either a 4-20 mA or 0-10V signal (transducer supplied by customer) applied to the VFD. Speed can also be manually controlled with a potentiometer or the VFD can be set for a fixed speed. • Each Compressor on a module must be protected by an individual manual reset overload between the VFD and the Compressor. • The overloads should be able to be set at a maximum of 26A. • If either overload opens, the VFD must be disabled. • The overloads must be configured for manual reset. • Normal full load run current for each Compressor on the module at 4800 rpm (80 Hz) is approximately 23A. • The customer control circuit must supply an Enable signal to the VFD before the drive will accept a Run Fwd signal. • The VFD will start when the Enable signal is on and a Run Fwd signal is applied. • The VFD will stop if the Run Fwd signal is off or the Enable signal is removed. NOTE The drive provides 24V for the Enable and Run Fwd signals. The installer must connect the Enable and Run Forward terminals to the drive’s 24V terminal. 10 2006SSD-75 R4 (10/10) Dual-Compressor Module Installation RED Blue White Yellow +24VDC DC common No connection feedback 0-10VDC speed signal 2.6.2 Oil Cooler Fan Control The Compressor Module temperature is controlled by managing module oil flow and temperature. The module’s precise temperature control is critical to system performance and equipment life. Maintaining proper temperature control also reduces the possibility of gas condensing into liquids during operation. • Cooling fans require 24VDC, 4.5A (105 Watts) x 2 (9A 210W total) for the Compressor Module. Fan speed is controlled by a 0-10VDC control signal that is applied to the yellow lead on the fan terminal strip. Standard Compressor Modules use a nonlinear PTC thermistor to monitor oil temperature and provide a speed signal. • High temperature Compressor Modules use a linear NTC thermistor to monitor oil temperature. This signal is available to support a customer-provided fan speed control circuit. • All power connections are wired to terminal strips in a junction box on the Compressor Module. Figure 6 Brushless DC Fan Figure 7 Basic Fan Control System Dropping Resistor One Fan 100 K Ohms Two Fans 60.4 K Ohms PTC Thermistor In Thermowell The PTC Thermistor is nonlinear and switches to high resistance in the 170-190°F (77-88°C) range. Red Wire – 24VDC Yellow Wire – 0-24VDC To fan speed control Blue Wire – DC Common 11 2006SSD-75 R4 (10/10) Dual-Compressor Module Installation Figure 8 Optional Customer-Installed High Temperature Fan Control System Power Supply 24VDC PLC Or Temperature Control SZO44 Compressor Module 0-10VDC Fan Speed Signal 0.9V = Off; 1.3V = 50%; 10V = 100% Temperature Sensor • Compressor requirements: 1.2 to 2 GPM (4.5-755 LPM) flow rate • Operating temperature range, standard: 190° to 210°F (88°- 99°C) • Thermal oil bypass valve, standard setting: 200°F (93°C) • Thermal bypass valve operation (valve’s purpose is to provide discharge temperature control) • Oil flow on valve is A to B when the unit is cold and A to C when the heat rises (see Figure 9). Figure 9 Oil Cooling and Thermal Valve A B C Oil Cooler Return 1st-Stage Separator to Compressor 12 2006SSD-75 R4 (10/10) Dual-Compressor Module Installation 2.6.3 Compressor Module Motor Protection Variable Speed Compressor Module Protection • The two Compressors in the variable speed Compressor Module should be treated as a single Compressor. Both Compressors must be run at the same time to prevent oil from accumulating in one Compressor. Module capacity can be changed by varying the typical Compressor speed, ranging from 2400 to 4800 rpm. • If two or more Compressor Modules are used together, each module can be considered as one Compressor and individual modules can be turned off. • Each Compressor on a variable speed Compressor Module requires independent overload protection between the VFD and Compressor. See 2.6.1 on page 10. Figure 10 Motor Control Variable Frequency Drive MS2 OL2 480VAC Variable Speed 480VAC Fixed Speed Drive Inhibit MS 1 & 2 Inhibit Compressor 2 Compressor 1 Compressor 2 Compressor 1 OL1 OL2 MS1 OL1 13 2006SSD-75 R4 (10/10) Dual-Compressor Module Installation Code Description 1 Control Techniques VFD,* 30 HP 2 24VDC po...

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