JOHNSON CONTROLS
32
FORM 160.81-NOM1
ISSUE DATE: 10/3/2020
SECTION 1 – INSTALLATION
drive coolant temperature, fail-closed, and set for a tem-
perature above dewpoint. It can be requested as factory-
supplied on a chiller order by special quotation.
Chilled Water Circuit
The minimum velocity through the tubes is 3 FPS
(feet per second) (0.914 MPS - meters per second), so
chilled water piping designs for variable flow should
be selected with higher velocities at design conditions.
The rate of change should be slow, to make sure that
the chiller controls can track the load.
The following is a guideline for an allowable variable
flow rate of change. This may require modification
based on specific design application.
The maximum allowable rate of change is 15 minutes
to go from 10% to 50% of design flow, based on a min-
imum chilled water system turnover rate of 15 minutes.
System turnover rate (STR) is a measure of the chilled
water system volume as compared to the design chilled
water flow rate, and is defined as:
System Turnover Rate (STR) =
Volume of chilled water system (gallons)
Design chilled water flow rate (gpm)
As noted previously, if the STR is above 15 minutes,
chilled water flow rate of change is 15 minutes. If
STR goes below 15 minutes, chilled water flow rate of
change must be modified as follows:
Rate of Change from 100% to 50% Flow (minutes) =
15 + 15 – STR
Chilled water supply must leave the evaporator through
the connection marked “Liquid Outlet”. Chilled water
return must enter the evaporator through the connec-
tion marked “Liquid Inlet”.
Condenser water supply must enter the condenser
through the connection marked “Liquid Inlet”. Con-
denser water return must leave the condenser through
the connection marked “Liquid Outlet”.
TABLE 10 -
WATER FLOW RATE LIMITS – GPM (L/S)
SHELL
CODE
PASS
EVAPORATOR
CONDENSER
MINIMUM
MAXIMUM
MINIMUM
MAXIMUM
TB, VB
1
383 (24.2)
1525 (96.2)
613 (38.7)
2204 (139.1)
2
192 (12.1)
0
762 (48.1)
307 (19.4)
1102 (69.5)
3
128 (8.1)
0
508 (32.1)
205 (12.9)
734 (46.3)
TC, VC
1
468 (29.5)
1866 (118.0)
683 (43.1)
2455 (154.9)
2
234 (14.8)
0
932 (58.8)
342 (21.6)
1227 (77.4)
3
157 (9.9)
0
621 (39.2)
228 (14.4)
818 (51.6)
TD, VD
1
570 (36.0)
2277 (143.7)
771 (48.7)
2774 (175.0)
2
286 (18.0)
1138 (71.8)
386 (24.4)
1386 (87.5)
3
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WB, XB
1
693 (43.7)
2771 (174.9)
866 (54.6)
3462 (218.5)
2
346 (21.8)
1385 (87.4)
433 (27.3)
1731 (109.2)
3
231 (14.6)
0
924 (58.3)
289 (18.2)
1154 (72.8)
WC, XC
1
822 (51.9)
3287 (207.4)
1082 (68.3)
4328 (273.1)
2
411 (25.9)
1644 (103.7)
541 (34.1)
2164 (136.5)
3
274 (17.3)
1096 (69.2)
361 (22.8)
1443 (91.1)
WD, XD
1
986 (62.2)
3945 (248.9)
1350 (85.2)
5400 (340.1)
2
493 (31.1)
1972 (124.4)
675 (42.6)
2700 (170.0)
3
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