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© 2015 Emerson Climate Technologies, Inc.
AE4-1387 R7
Compressor Tubing and Mounting
Compressor mounting must be selected based on
application. Consideration must be given to sound
reduction and tubing reliability. Some tubing geometry
or “shock loops” may be required to reduce vibration
transferred from the compressor to external tubing.
Starting Characteristics
Single-phase scroll compressors are designed with
permanent split capacitor (PSC) type motors and
therefore will start without the need of start assist
devices in most applications. However, if low voltage
conditions exist at start up, protector trips can result.
Therefore, start assist devices (start capacitors and
relays) are available to maximize starting characteristics
under abnormal conditions. See
Table 8
for voltage
ranges.
Fusite
Fusite pin molded orientation for single-phase and
three- phase refrigeration scroll compressors are shown
in
Figure 4
.
Shell Temperature
System component failure may cause the top shell
and discharge line to briefly reach temperatures above
300°F. Wiring or other materials, which could be
damaged by these temperatures, should not come in
contact with the shell.
Connection Fittings
Scroll compressors are provided only with sweat
connections. (Consult your Emerson Climate
Technologies representative for details).
See section on
New Installation
for suggestions on
how to properly braze these fittings.
Three-Phase Rotation Direction
Scroll compressors are directional dependent: i.e., they
will compress in one rotational direction only. On single-
phase compressors, this is not an issue since they will
only start and run in the proper direction (except as
described in the Labeled Brief Power Interruptions).
Three-phase scrolls, however, will rotate in either
direction depending on the power of the phasing. So
there is a 50/50 chance of connected power being
“backwards.” Contractors should be warned of this.
Appropriate instructions or notices should be provided
by the Original Equipment Manufacturer.
Verification of proper rotation can be made by observing
that the suction pressure drops and the discharge
pressure rises when the compressor is energized.
Additionally, if operated in reverse the compressor is
noisier and its current draw is substantially reduced
compared to tabulated values.
Although operation of scroll in reverse direction for brief
periods of time is not harmful, continued operation could
result in failure.
All three-phase compressors are wired identically
internally. Once the correct phasing is determined for
a specific system or installation, connecting properly
phased power leads to the same fusite terminals will
maintain the proper rotation.
Brief Power Interruptions
Brief power interruptions (less than ½ second) may
result in powered reverse rotation of single-phase
refrigeration scroll compressors. High-pressure
discharge gas expands backward through the scrolls
at power interruption causing the scroll to orbit in
the reverse direction. If power is reapplied while this
reversal is occurring, the compressor may continue to
run noisily in the reverse direction for several minutes
until the compressor internal protector trips. This has no
negative effect on durability. When the protector resets,
the compressor will start and run normally.
Emerson strongly encourages the use of a timer
which can sense brief power interruptions and lock the
compressor out of operation for two minutes. A typical
timer circuit is shown in
Figure 5
.
No time delay is required on three phase models to
prevent reverse rotation due to power interruptions.
Deep Vacuum Operation
WARNING
Do not run a refrigeration scroll compressor in
a deep vacuum. Failure to heed this advice can
result in permanent damage to the compressor.
A low-pressure control is required for protection against
deep vacuum operation. See the section on pressure
controls for the proper set points. (See
Table 5
)
Scroll compressors (as with any refrigeration
compressor) should never be used to evacuate
refrigeration or air conditioning systems. See
AE24-
