York YCAV0157, Installation Operation & Maintenance

Page: 174 / 310

174
JOHNSON CONTROLS
FORM 201.21-NM1 (1223)
MINIMUM VSD COMPRESSOR START/RUN FREQUENCY
MINIMUM VSD START FREQUENCY
The Minimum VSD Compressor Start Frequency is
based on ambient temperature and determines the
frequency (speed) the compressor(s) is ramped to at start.
At higher ambients, higher speeds are needed to provide
adequate motor cooling. At low ambients, higher motor
speeds are needed to develop oil pressure differential at
start. The temperature ranges and the associated start
frequency follows the guidelines below:
·
If the ambient temperature is 25°F or less, the
Minimum VSD Start Frequency will be
70 Hz.
· If the ambient temperature is 26-40 °F, the
Minimum VSD Start Frequency is 60 HZ.
·
If the ambient temperature is 41-110 °F, the
Minimum VSD Start Frequency will be
50 Hz.
· If the ambient is 110-125 °F, the Minimum VSD
Start Frequency is scaled according to the
following formula:
(3X Ambient Temperature)-280°F.
The formula is also represented by the graph in FIG.
30.
NOTE: The graph above also illustrates the scaled frequency:
FIG. 30 - MINIMUM VSD START FREQUENCY
LD10627
40
45
50
55
60
65
70
75
80
85
90
95
100
105 110 115 120 125 130
Ambient Temperature (°F)
Mi
ni
mu
m
VSD
F
re
que
ncy
(H
z)
NOTE: The graph above also illustrates the scaled frequency:
FIG. 31 - MINIMUM VSD RUN FREQUENCY
LD10628
40
45
50
55
60
65
70
75
80
85
90
95
100
105 110 115 120 125 130
Ambient Temperature (°F)
Mi
ni
mu
m
VSD
F
re
que
ncy
(H
z)
MINIMUM VSD RUN FREQUENCY
The Minimum VSD Compressor Run Frequency is based
on ambient temperature and determines the minimum
frequency (speed) the compressor(s) is permitted to run
as the system unloads. At high ambients, higher motor
speeds are needed to cool the compressor motor. The
temperature ranges and the associated start frequency
follows the guidelines below:
· If the ambient temperature is <110°F, the Minimum
VSD Run Frequency will be 50 Hz.
·
If the ambient is 110-125°F, the Minimum VSD
Run Frequency is scaled according to the following
formula:
(3X Ambient Temperature)-280°F.
The formula is also represented by the graph in FIG.
31.
OPERATION
· Above 125°F, the minimum VSD Start
Frequency is 95 Hz.
·
If the ambient temperature is >125°F, the Minimum
VSD Run Frequency will be 95 Hz.