SECTION 9 - MAINTENANCE
JOHNSON CONTROLS
163
Form 201.47-ICOM1
Issue date: 17/11/2022
9
Callout Component Callout Component
A Compressor
discharge line
isolation ball valve
B Condenser
drain liquid
service valve
C Liquid line
angle valve
D Suction service
valve (Optional)
System pressure test
With the refrigerant charge removed and all known
leaks repaired, charge the system with a small amount
of refrigerant mixed with dry nitrogen. You can then
use an electronic leak detector to detect any leaks that
are too small to be found by the soap test.
Care must be taken to not exceed the rated
pressure of the unit refrigerant pressure
relief valves.
Conducting the gas pressure hold test
1. To monitor the system pressure over time, install
a high-quality, high-resolution analog pressure
gauge on one of the service valves. Use a pressure
gauge that has a resolution of 2 psi increments
with a dial face at 3 in. in diameter or greater.
2. Ensure all the system valves including manual
valves and EEVs are 100% open. Make sure that
caps in place, if applicable.
3. Before proceeding, make sure that the unit is at
the initial evacuation level of 5 mmHg.
Important: To prevent freezing of any moisture
that may inhibit the system, do not go below 5
mmHg. See System evacuation on page 165 for
more details.
4. With the system in a vacuum, slowly charge nitro-
gen vapor only into the system.
5. Slowly build up the system pressure with dry ni-
trogen to the design working pressure (DWP) as
found on the chiller vessel data plates.
6. Allow the pressure to remain in the chiller based
on Figure 28. This chart provides the hold times
for pressure hold testing based on the vessel diam-
eter and length.
What to do next
• For a unit with no loss of pressure, proceed to unit
evacuation.
• For units where a leak is suspected and there is
any amount of drop in recorded pressure, proceed
to either of the following leak detection methods:
Conducting the soap visual gas leak test or Con-
ducting the optional trace gas leak test.
Figure 64 - Leak test hold times
Conducting the soap visual gas leak test
1. To monitor the system pressure over time, install
a high-quality, high-resolution analog pressure
gauge on one of the service valves. Use a pressure
gauge that has a resolution of 2 psi increments
with a dial face at 3 in. in diameter or greater.
2. Ensure all the system valves including manual
valves and EEVs are 100% open. Make sure that
caps in place, if applicable.
3. Before proceeding, make sure that the unit is at
the initial evacuation level of 5 mmHg.
Important: To prevent freezing of any moisture
that may inhibit the system, do not go below 5
mmHg. See System evacuation on page 165 for
more details.
4. With the system evacuated, connect the hoses to
high and low side of the system and charge with
dry nitrogen to 100 psig (690 kPa). Pressure can
be increased up to 150 psig to detect very small
leaks.
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