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Figure 5. Drain Line
Refrigeration Piping
Suction Lines
NOTE: If the suction line must rise to the point higher than the suction connection on
the evaporator, a suction line trap at the outlet of the evaporator must be provided.
Horizontal suction lines should slope away from the evaporator toward the compressor at the rate of 1/4’ per 10 feet
for good oil return. When multiple evaporators are connected in series using a common suction line, the branch
suction lines must enter the top of the common suction line.
Suction lines that are outside of refrigerated space must be insulated. See “Line Insulation” for more information.
Suction Line Risers
NOTE: To provide proper oil return, a suction trap must be provided at the base of
all suction risers.
Prefabricated wrought copper traps are available, or a trap can be made by using two street ells and one regular ell.
The suction trap must be the same size as the suction line. For long vertical risers, additional traps may be necessary.
Generally, one trap is recommended for each length of pipe (approximately 20 feet) to insure proper oil movement.
See Figure 4 below for methods of constructing proper suction line P-traps.
Condensate Drain Lines
Copper drain lines should be used and properly protected from freezing. In running drain lines, provide a minimum
of 4 inches per foot pitch for proper drainage. Drain lines should be at least as large as the evaporator drain
connection. All plumbing connections should be made in accordance with local plumbing codes. All condensate
drain lines must be trapped, and run to an open drain. They must never be connected directly to the sewer
systems. Traps in the drain line must be located in a warm ambient. We recommend a trap on all evaporators. Traps
located outside, or extensive outside runs of drain line must
be wrapped with a drain line heater. The heater should be
connected so that it is continuously on. It is recommended that
the drain line be insulated to prevent heat loss. A heat input
of 20 watts per lineal foot of drain line for 0ºF (-18°C) room
applications and 30 watts per lineal foot for -20°F (-29°C) rooms
is satisfactory.
Inspect the drain pan periodically to insure free drainage of
condensate. If the drain pan contains standing water, check for
proper installation. The drain pan should be cleaned regularly
with warm soapy water.
WARNING: All power must be disconnected
before cleaning. The drain pan also serves as
cover for hazardous moving parts. Operation
of unit without drain pan constitutes a hazard.
Figure 4. Suction P-traps
NOTE: Always trap drain lines individually
to prevent vapor migration.