JOHNSON CONTROLS
74
FORM 160.67-O2
ISSUE DATE: 10/9/2020
SECTION 6 - MAINTENANCE
CONDUCTING R-22 PRESSURE TEST
With the R-134a charge removed and all known leaks
repaired, the system should be charged with a small
amount of R-22 mixed with dry nitrogen so that an
electronic leak detector can be used to detect any leaks
too small to be found by the soap test.
To test with R-22, proceed as follows:
1.
Valve off the water side of the evaporator and
refrigerant condenser and blow down the bundle
pressure to 0 PSIG.
2. With no pressure in the system, charge R-22 gas
into the system through the charging valve to a
pressure of 2 PSIG.
3. Build up the system pressure with dry nitrogen to
approximately 75 to 100 PSIG (517 to 690 kPa).
To be sure that the concentration of refrigerant
has reached all parts of the system, slightly open
the oil charging valve (If oil charge is not present)
and test for the presence of refrigerant with a leak
detector.
Do not open the oil charging valve if oil
charge has not been drained. Test for
R-22 at the condenser service valve if oil
charge is present.
4. Test around each joint and factory weld. It is im-
portant that this test be thoroughly and carefully
done, spending as much time as necessary and us-
ing a good leak detector.
5.
Check if any pressure buildup has occurred in
the water side of the evaporator and condenser.
Open the vents in the evaporator and condenser
heads and test for the presence of refrigerant. If
no refrigerant is present, the tubes and tube sheets
may be considered tight. If refrigerant is detected
at the vents, the heads must be removed, the leak
located (by means of soap test or leak detector) and
repaired.
VACUUM TESTING
After the pressure test has been completed, the vacuum
test should be conducted as follows:
1. Connect a high capacity vacuum pump, and an
indicator to the system as shown in
FIG. 15 and
start the pump. (See “Vacuum Dehydration”.)
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
until a wet bulb
temperature of +32°F or a pressure of 5 mm Hg
is reached. See Table 4 for corresponding values
of pressure.
4. To improve evacuation circulate hot water (not
to exceed 125°F, 51.7ºC) through the evaporator
and condenser tubes to thoroughly dehydrate the
shells. If a source of hot water is not readily avail-
able, a portable water heater should be employed.
DO NOT USE STEAM
. A suggested method is
to connect a hose between the source of hot water
under pressure and the evaporator head drain con-
nection, out the evaporator vent connection, into
the condenser head drain and out the condenser
vent. To avoid the possibility of causing leaks, the
temperature should be brought up slowly so that
the tubes and shell are heated evenly.
5.
Close the system charging valve and the stop
valve for the vacuum indicator. Then disconnect
the vacuum pump leaving the vacuum indicator
in place.
6.
Hold the vacuum obtained in Step 3 in the system
for 8 hours; the slightest rise in pressure indicates a
leak or the presence of moisture, or both. If, after 24
hours the wet bulb temperature in the vacuum indi-
cator has not risen above 40°F (4.4°C) or a pressure
of 6.3 mm Hg, the system may be considered tight.
Be sure the vacuum indicator is valved off
while holding the system vacuum and be
sure to open the valve between the vacuum
indicator and the system when checking
the vacuum after the 8 hour period.
7.
If the vacuum does not hold for 8 hours within the
limits specified in Step 6 above, the leak must be
found and repaired.
VACUUM DEHYDRATION
To obtain a sufficiently dry system, the following in-
structions have been assembled to provide an effective
method for evacuating and dehydrating a system in the
field. Although there are several methods of dehydrat-
ing a system, we are recommending the following, as
it produces one of the best results, and affords a means
of obtaining accurate readings as to the extent of de-
hydration.
