Emerson SCROLL SZO44 - Manual (Page 18)

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 2 Compressor 1
Compressor 1
OL1 OL2 MS1
OL1