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2.18. Refrigerant Piping Protection
The refrigerant in the system(s) is under high-pressure and this pressure can rapidly increase if
the refrigerant is unintentionally confined (or trapped) between isolation devices such as service
valves, liquid line solenoid valves, expansion valves, etc. If the ambient temperature surrounding
the piping system increases, this may cause the contained refrigerant pressure to increase to
an unacceptable level.
WARNING:
This increased pressure can cause piping ruptures,
discharge of refrigerant, pollution, equipment damage, injury or death.
Use extreme caution when:
1. Installing the piping lines and make certain that these isolation
devices are open to prevent unintended containment (trapping) of
refrigerant.
2. When charging a refrigerant system,
do not exceed the Design
Pressure
indicated on the unit nameplate.
3. Ensure that pressure has a path to expand when cutting or making
connections, disconnections and piping repairs.
The installing contractor must review the piping system and guard against these possible areas
where the refrigerant could be confined. If the areas cannot be vented and allow the refrigerant
to expanded freely or eliminate pressure increases, the installing contractor must field supply
pressure relief devices.
Additionally, the installing contractor must consult local building and piping codes regarding
installing pressure-safety devices in the required areas of the piping system(s) that could be
unintentionally isolated during field installation, maintenance or repairs of the refrigerant
systems.
A
fter a “Direct Type” Relief Device has discharged once, it should be replaced. The “Direct
Type” Relief Device is designed to reclose automatically at a predetermined pressure, but
reliability of the device to reseal tightly and to operate at the designed pressure cannot be
guaranteed after discharging. Be safe and replace the device after such an occurrence.
NOTE:
Receivers are often installed on condensers and condensing units.
The receiver includes a safety pressure-device to protect the receiver, but
the receiver also includes service valves which, if closed, will isolate this
pressure-safety device and only protect the receiver. If these valves are
closed, the rest of the piping system would not be protected from
unintended refrigerant pressure in- creases. Again, the installing contractor
must review the piping system and guard against trapping the refrigerant
by installing field supplied pressure-safety devices.