175
JOHNSON CONTROLS
FORM 201.21-NM1 (1223)
ACCELERATION/DECELERATION RATE WHEN
STARTING/STOPPING COMPRESSORS
VSD ACCELERATION AND
DECELERATION RATES
The acceleration rate changes with frequency and fol-
lows the guidelines below:
· Between 0 and 50 Hz, the acceleration is 10 Hz/
sec.
· Between 50 and 200 Hz, the acceleration is 30.4
Hz/sec. Even though the accel rate of 30.4 Hz/sec
is possible up to 200 Hz, the frequency (speed) is
limited by the minimum start frequency and the
add a compressor frequency calculation performed
by the micro when bringing on an additional
compressor.
When decelerating, the deceleration rate changes with
frequency and follows the guidelines below:
· Between 200 and 100 Hz, the deceleration time is
30.4 Hz/sec.
· Between 100 and 0 Hz, the deceleration time is 10
Hz/sec.
When a compressor stops, back-spin of the compressor
will often occur as the pressure dierential between
discharge and suction equalizes. This should not be a
cause of concern.
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