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Oil Traps
To ensure proper oil return to the compressor, a P-type oil trap should be installed at the base of each suction riser of
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four feet or more.
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The suction trap must be the same size as the suction line.
Additional traps are necessary for long vertical risers. Add a trap for each length of pipe (approximately 20 feet) to
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insure proper oil return.
Suction lines must slope ¼" per 10 feet toward the compressor.
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Install a suction line trap at the evaporator outlet if the suction line rises to a point higher than the connection on the
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evaporator.
Failure to properly install oil traps can prevent sufficient oil return to the compressor resulting in premature compressor
failure.
Drain Lines
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Evaporator coil drain lines should be pitched a minimum of 1/2" per foot to allow proper drainage and exit the walk-in
as quickly as possible.
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Insulate and seal the drain line where it passes through the wall.
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Copper drain line is required.
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Freezer compartment drain lines must have heat tape wrapped around the copper drain line and must have ¾" thick
insulation tubing.
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Do not locate drain line P-traps within the freezer space.
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Do not reduce the drain line size.
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Locate a drain line P-trap outside of the cooler space.
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Any outdoor P-traps exposed to low ambient temperatures should be wrapped with a drain line heater (provide 20
watts of heat per foot of drain line at 0°F, 30 watts per foot at -20°F.
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Freezer/cooler combo boxes can have one common drain line. However, there must be a P-trap located between the
freezer evaporator and the cooler evaporator located inside the cooler compartment.
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The cooler compartment P-trap should be located between the cooler evaporator and the external drain location.
CAUTION
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