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12) If the vacuum hold test fails use Table 32 to determine if the failure is due to a leak or
water/moisture in the unit. If the vacuum level rises above water saturation point then do another
leak test. If it stops at water saturation temperature, continue evacuation until dry or source
determined.
Table 23, Pressure Chart
GAGE
PRESSURE
VACUUM
in. Hg
0
10.24
22.05
25.98
27.95
28.94
29.53
29.72
29.74
29.842
29.882
29.901
29.909
29.917
29.919
29.9206
29.921
Notes:
1.
psia ( pounds per square inch absolute ): sum of gage and atmospheric pressures
2.
psig ( pounds per square inch gage ): pressure over atmospheric pressure
3.
vacuum: pressure below atmospheric i.e. negative gage pressure (always stated as positive numbers)
4.
in. Hg: inches of mercury, mm Hg: millimeters of mercury
Charging the System
WCT water chillers are leak tested at the factory and the correct charge of refrigerant is indicated on
the nameplate.
In the event the refrigerant charge was lost due to leak(s) or the unit exhibits a lack of performance
due to insufficient amount of charge, the system should be charged or trimmed.
In order to ease the evacuation, charging and trimming, service connection valves are provided at the
top and bottom of condenser and evaporator and at the bottom of economizer as well as sight glasses
on the evaporator, economizer, and condenser.
If there are any leaks found then first repair the leaks.
If the system is evacuated due to service and is still under a vacuum then in order to put charge back
into the system follow these steps which are applicable for both circuits :
1.
Make up a suitable charging connection from new copper tubing or yellow jacket/flexible hose
to fit between the chiller charging valve and the fitting on the refrigerant charging cylinder. This
connection should be as short as possible but long enough to permit sufficient flexibility for
charging cylinders.
OMM WCT
ABSOLUTE PRESSURE
psia
in. Hg
14.696
29.921
( Std. at Sea Level )
9.668
19.68
3.867
7.87
1.934
3.94
0.967
1.97
0.483
0.98
0.193
0.39
0.097
0.20
0.089
0.18
0.039
0.08
0.019
0.04
0.010
0.02
0.006
0.01
0.002
0.004
0.001
0.002
0.0002
0.0004
0
0
Centrifugal Chillers
mm Hg
Microns
760
760,000
500
500,000
200
200,000
100
100,000
50
50,000
25
25,000
10
10,000
5
5,000
4.58
4,580
2
2,000
1
1,000
0.50
500
0.30
300
0.10
100
0.05
50
0.01
10
0.00
0
WATER TEMPERATURE AT
o
SATURATION
F
212 (Water Boiling Temperature)
192
152
125
101
78
52
34
32 (Water Freezing Temperature)
15
1
-11
-20
-38
-50
-73
D-EOMWC01302-16EN - 74/84
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