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45
FLOW RATE REQUIREMENTS — Standard chillers should
be applied with nominal flow rates within those listed in the
Minimum and Maximum Cooler Flow Rates table. Higher or
lower flow rates are permissible to obtain lower or higher
temperature rises. Minimum flow rates must be exceeded to
assure turbulent flow and proper heat transfer in the cooler. See
Table 34.
Consult application data section in the Product Data
literature and job design requirements to determine flow rate
requirements for a particular installation.
OPERATION
Sequence of Operation —
With a command to start
the chiller, the cooler pump will start. After verifying water
flow, the control will monitor the entering and leaving water
temperature. At any time that a compressor is not operating, its
crankcase heater is active. If the need for mechanical cooling is
determined, the control decides which circuit and compressor
to start. The compressor will deenergize the crankcase heater as
it starts. Compressors will be staged with minimum load
control (if equipped and configured) to maintain LWT set
point.
Shutdown of each circuit under normal conditions occurs in
increments, starting with the minimum load control (if
equipped) and finishing with the last running compressor. Once
minimum load control is disabled, one compressor is
shut down. Eight seconds later the next compressor will
shut down. The process will continue until all of the compres-
sors are shut down. The EXV will close completely, 1 minute
after the last compressor has shut down. There are several
abnormal conditions that, if detected, will shut down the circuit
immediately. In this case, minimum load control and all
compressors are turned off
without
an 8-second interval
between them. The cooler pump will remain ON for 20 sec-
onds after the last compressor has been turned OFF.
Dual Chiller Sequence of Operation —
With a
command to start the chiller, the master chiller determines
which chiller will become the lead chiller based on
Configura-
tion
RSET
LLBL
and
Configuration
RSET
LLBD
.
The lead chiller is always started first and the lag chiller is held
at zero percent capacity by the master chiller forcing the lag de-
mand limit value to 0%. The lead chiller’s water pump will be
started. The lag chiller’s water pump shall be maintained off if
Configuration
RSET
LAGP
=
0
. The internal algorithm of
lead chiller will control capacity of the lead chiller.
If Lead Pulldown Time (
Configuration
RSET
LPUL
)
has been configured, the lead chiller will continue to operate
alone for that specified time. After the Lead Pulldown Time
timer has elapsed, if the lead chiller is fully loaded and either
all available compression is on or at the master demand limit
value, then the lag start timer (
Configuration
RSET
LLDY
) is initiated. When the pulldown timer and lag start
timer have elapsed and the Combined Leaving Chilled Water
Temperature is more than 3° F (1.7° C) above the set point,
then the lag chiller is started.
Table 34 — Minimum and Maximum Cooler Flow Rates
SIZES 060-300
SIZES 315-390
CAUTION
Operation below minimum flow rate could subject tubes to
frost pinching in the tube sheet, resulting in failure of the
cooler.
30RB
SIZE
MINIMUM
COOLER
FLOW RATE
(gpm)
MAXIMUM
FLOW RATE
(gpm)
MINIMUM
LOOP
VOLUME
(gal.)
MINIMUM COOLER
FLOW RATE
(l/s)
MAXIMUM
COOLER
FLOW RATE
(l/s)
MINIMUM
LOOP
VOLUME
(liters)
060
72
288
180
5
18
681
070
84
336
210
5
21
795
080
96
384
240
6
24
908
090
108
432
270
7
27
1022
100
120
480
300
8
30
1136
110
132
528
330
8
33
1249
120
144
576
360
9
36
1363
130
156
624
390
10
39
1476
150
180
720
450
11
45
1703
160
192
768
480
12
48
1817
170
204
816
510
13
51
1931
190
228
912
570
14
58
2158
210
252
1008
630
16
64
2385
225
270
1080
675
17
68
2555
250
300
1200
750
19
76
2839
275
330
1320
825
21
83
3123
300
360
1440
900
23
91
3407
30RB
SIZE
MINIMUM COOLER
FLOW RATE
(gpm)
MAXIMUM COOLER
FLOW RATE
(gpm)
MIN
LOOP
VOLUME
(gal.)
MINIMUM COOLER
FLOW RATE
(l/s)
MAXIMUM COOLER
FLOW RATE
(l/s)
MIN
LOOP
VOLUME
(liters)
Module A
Module B
Module A
Module B
Module A
Module B
Module A
Module B
315
192
192
768
768
945
12
12
48
48
3577
330
192
204
768
816
990
12
13
48
51
3748
345
204
204
816
816
1035
13
13
51
51
3918
360
204
228
816
912
1080
13
14
51
58
4088
390
228
228
912
912
1170
14
14
58
58
4429
Summary of Contents for AQUASNAP 30RBA315
Page 77: ...77 Fig 37 Control Schematic 30RB060 080 a30 4619...
Page 78: ...78 Fig 38 Control Schematic 30RB090 150 a30 4620...
Page 79: ...79 Fig 39 Control Schematic 30RB160 190 a30 4622...
Page 80: ...80 Fig 40 Control Schematic 30RB210 300 a30 4622...
Page 81: ...81 Fig 41 Heat Reclaim Control Schematic a30 4622...