Nor-Lake Refrigeration Systems - Manual (Page 6)

09/14 Rev. E 101628 6
REFRIGERANT LINES
After the condensing unit and the evaporator coil are mounted in their respective positions, the
refrigerant lines may be installed. The positions of the refrigerant lines relative to horizontal is
important in guaranteeing oil return to the compressor. The three possible relative positions are as
follows:
1. Condensing unit above the evaporator coil
2. Condensing unit on the same horizontal plane as the evaporator coil
3. Condensing unit below the evaporator coil
Caution: Tubing entrance holes must be positioned to clear any panel section joint or panel metal
seam, and should not fall within a six-inch radius from the center of any panel lock access hole. See
Figure 1 on page 4.

Suction Lines: The suction line is the most critical line from a design and construction
standpoint. The suction line must be sized to maintain proper line velocities and practical line
pressure drop. To ensure proper oil return, all horizontal lines should slope downward towards
the compressor with a slope of 1/2” per ten feet. Horizontal lines can be increased one or two
sizes for long runs. When the condensing unit is installed above the evaporator coil, an oil trap
should be built into the suction line before the first riser. Additional oil traps should be installed for
each additional 20 feet of rise. Refer to Table 2 or 3 to determine the proper size suction line and
riser size.
Suction lines must be insulated. Use good quality insulation such as Rubatex or Armaflex
Tubing Insulation. Recommended wall thickness should be 3/4”. During installation, the ends
of the insulation must be taped off and sealed to prevent condensation build up.
Determining Size of Suction Line:
1. Determine the approximate length (±10%) of the suction line from a sketch of the
proposed installation.
2. From Table 2 for R-404, along the top of the table, find the appropriate suction
temperature. Using the suction line length, round up to the nearest length matching one
listed on the chart in the section under the selected temperature. This is the correct
column to use.
3. Along the side of the table, find the system capacity in BTU/Hr. When the correct
capacity is found, follow the row over to where it intersects with the column found in step
2. This is the size of the line. Caution: This may not be the final answer. Continue
with the following steps.
4. Determine the number of shut-off valves, globe or angle, elbows, and tees that will be
used in the suction line from the installation sketch completed in step 1.
5. From Table 1, establish the equivalent feet of pipe for the total number of each type of
valve and fitting. Based on the line size determined in step 3, find this line size along the
top of the table and the valve or fitting along the left side. Where these two intersect is
the equivalent number of feet.
6. Add together the total length of suction line from step 1 and the equivalent length in feet
of the valves and fittings from step 5.
7. Using the new total length calculated in step 6, repeat steps 2 and 3 to determine the
line size based on this new length, instead of using the length of the suction line only.
This is now the final answer and the line size to use. Note: steps 2 and 3 were done the
first time to get the approximate line size needed to calculate the valve and fitting
equivalents in step 5.
8. The line size determined in step 7 is the recommended size to hold the pressure drop
within permissible limits.