TP-107D
Page 2 of 5
4. Liquid Line Solenoid - a long line set application can critically increase the charge level
needed for a system. As a result, the system is very prone to refrigerant migration during its
off-cycle and a liquid line solenoid will help minimize this. A liquid line solenoid is
recommended for any long line application on straight cooling units.
Tube Sizing:
1. In long line applications, the “equivalent line length” is the sum of the straight length
portions of the suction line plus losses (in equivalent length) from 45 and 90 degree bends.
Select the proper suction tube size based on equivalent length of the suction line
(see Tables 2 & 3) and recalculated system capacity.
TABLE 1.
Equivalent length = Length
horizontal
+ Length
vertical
+ Losses from bends (see Table 3)
Example using ¾” elbow:
150 feet of straight tubing + (four short radius elbows x 1.7) + (2 long radius elbows
x 1.5) = 150 + 3.4 +3 = 156.4 equivalent feet.
2. For any residential split system installed with a long line set, 3/8” liquid line size
must be used. Limiting the liquid line size to 3/8” is critical since an increased refrigerant
charge level from having a larger liquid line could possibly shorten a compressor’s lifespan.
3. Single Stage Condensing Unit: The maximum length of tubing must not
exceed 150 feet.
• 80 feet is the maximum recommended vertical difference between the condenser and
evaporator when the evaporator is above
the condenser. Equivalent length is not to
exceed 150 feet.
• The vertical difference between the condenser and evaporator when the evaporator is
below the condenser can approach 150 feet, as long as the equivalent length does not
exceed 150 feet.
• The distance between the condenser and evaporator in a completely horizontal
installation in which the indoor and outdoor unit do not differ more than 10 feet in vertical
distance from each other can approach 150 feet, as long as the equivalent length does
not exceed 150 feet.
4. Two-Stage Condensing Unit: The maximum length of tubing must not exceed 80 feet
where indoor coil is located above the outdoor unit.
NOTE: When the outdoor unit is located above the indoor coil, the maximum vertical rise
must not
exceed 25 feet. If the maximum vertical rise exceeds 25 feet, premature
compressor failure will occur due to inadequate oil return.
Most refrigerant tubing kits are supplied with 3/8”-thick insulation on the vapor line. For long line
installations over 80 feet, especially if the line set passes through a high ambient temperature,
½”-thick suction line insulation is recommended to reduce loss of capacity. The liquid line should
be insulated if passing through an area of 120°F or greater. Do not attach the liquid line to any
non-insulated portion of the suction line.
5. Vibration and Noise: In long line applications, refrigerant tubing is highly prone to transmit
noise and vibration to the structure it is fastened to. Use adequate vibration-isolating
hardware when mounting line set to adjacent structure.
(66 pages)
(5 pages)
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