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Section 3 - Maintenance
Table 1 - System pressures
*Gauge
Inches of
mercury (Hg)
below one
standard
atmosphere
0 in.
10.240 in.
22.050 in.
25.980 in.
27.950 in.
28.940 in.
29.530 in.
29.670 in.
29.720 in.
29.842 in.
29.882 in.
29.901 in.
29.917 in.
29.919 in.
29.9206 in.
29.921 in.
*One standard atmosphere
Vacuum testing
Ensure power is removed from the input
side of the VSD at all times when the
chiller is under vacuum (less than atmo-
spheric pressure). The VSD maintains
voltage to ground on the motor when the
chiller is off while voltage is available to
the VSD. Insulating properties in the mo-
tor are reduced in vacuum and may not
insulate this voltage sufficiently.
After the pressure test has been completed, the vacuum
test should be conducted as follows:
1. Connect a high capacity vacuum pump, with in-
dicator, to the system charging valve as shown in
18
psia
14.6960
9.6290
3.8650
1.9350
0.9680
0.4810
0.1920
0.1220
0.0990
0.0390
0.0190
0.0100
0.0020
0.0010
0.0002
0
= 14.696 psia
= 760 mm Hg absolute pressure at 32°F
= 29.921 in. Hg absolute at 32°F
Absolute
Millimeters
of mercury
Microns
(Hg)
760.00
760,000
500.00
500,000
200.00
200,000
100.00
100,000
50.00
50,000
25.00
25,000
10.00
10,000
6.30
5.00
2.00
1.00
0.50
0.10
0.05
0.01
0
Notes:
Figure 5 and start the pump. See Vacuum dehy-
dration in this section.
2. Open wide all system valves. Be sure all valves to
the atmosphere are closed.
3. Operate the vacuum pump in accordance with
Vacuum dehydration in this section until a wet
bulb temperature of 32°F (0°C) or a pressure of 5
mm Hg is reached. See Table 1 for corresponding
pressure values.
4. To improve evacuation circulate hot water, not
to exceed 125°F (51.7ºC) through the evapora-
tor and condenser tubes to thoroughly dehydrate
Issue date: 05/19/2021
Boiling
temperatures
of
water
°F
212
192
151
124
101
78
52
6,300
40
5,000
35
2,000
15
1,000
1
500
-11
100
-38
50
-50
10
-70
0
psia
= lb per sq. in. gauge pressure
= Pressure above atmosphere
psia
= lb per sq. in. absolute pressure
= Sum of gauge plus atmospheric
pressure
JOHNSON CONTROLS
Form 160.78-O1
Water
Freezes
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