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7.3 Piping Considerations
7.3.1 Refrigerant Loop
All split systems require two refrigerant lines (an insulated copper suction line and a copper liquid
line) between the evaporator and the condensing unit.
Two possible methods exist for installing the copper suction and liquid lines.
1. Using an optional Sweat Adapter Kit and hard piping between the two units.
2. Using optional pre-charged line sets.
All refrigeration piping should be installed with high temperature brazed joints. Prevailing good
refrigeration practices should be employed for piping supports, leak testing, evacuation, dehydration,
and charging of the refrigeration circuits. The refrigeration piping should be isolated from the build-
ing by the use of vibration isolating supports.
It is important to handle the pre-charged lines with care so they will not get kinked or damaged. Use
tube benders and make all bends before making connections to either end. Coil any excess tubing in a
horizontal plane with the slope of the tubing toward the condensing unit.
To prevent tube damage when sealing openings in walls and to reduce vibration transmission, use a
soft flexible material to pack around the tubes.
When installing remote condensing units mounted above the evaporator, the suction gas line should
be trapped at the evaporator. This trap will retain refrigerant oil in the off cycle. When the unit
starts, oil in the trap is carried up the vertical riser and returns to the compressor.
Refrigerant charge requirements: Total refrigerant charge will be required only if units are evacuated
during installation or maintenance. Total refrigerant charge = evaporator + lines + condensing unit.
!
CAUTION
All local codes for handling refrigerant must be followed.
NOTE
As R22 and R407C are similar in properties, proper safety equipment and proper refrigeration
tools are required on both types. Check unit nameplate for correct refrigerant type before
topping off or recharging a system.
NOTE
Refrigerant R407C uses a POE (polyol ester) lubricant. The R407C refrigerant must be
introduced and charged from the cylinder only as a liquid.
NOTE
When installing field piping, care must be taken to protect all refrigerant lines from the
atmosphere, especially when using refrigerants with POE oils. Do not allow the piping to stand
open to air for more than 15 minutes. Units designed for R407C have a compressor which
contains POE oil that is very hygroscopic; that is, it quickly absorbs water from the air. The
longer the compressor piping is left open to air, the harder it will be to fully evacuate. If left
open too long, the POE oil may need to be replaced before achieving the required vacuum level.
NOTE
Complete all piping and evacuate lines before connecting quick connects when using an
optional sweat adapter kit and field installed hard piping.
Follow all proper brazing practices including a dry nitrogen purge to maintain system
cleanliness.
NOTE
All condensing units and 3-ton evaporator units are fully charged with refrigerant. All
23 and 33 kW evaporator units include a nitrogen holding charge only. See Table 19 for field
charge required. If field-supplied refrigerant piping is installed, refrigerant must be added to
the system.