Goodman ASX Service Instructions Manual page 66

SERVICING
4. Two-Stage Condensing Unit: The maximum length of
tubing must not exceed 75 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 inad-
equate oil return.
5. Vibration and Noise: In long line applications, refriger-
ant 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.
Most refrigerant tubing kits are supplied with 3/8"-thick
insulation on the vapor line. For long line installations over 50
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.
Table 4 lists multiplier values to recalculate system-cooling
capacity as a function of a system's equivalent line length (as
calculated from the suction line) and the selected suction
tube size. Table 5 lists the equivalent length gained from
adding bends to the suction line. Properly size the suction
line to minimize capacity loss.
TABLE 4. CAPACITY MULTIPLIERS AS A FUNCTION OF
SUCTION LINE SIZE & EQUIVALENT LENGTH
Nominal Vapor line
capacity diameter
Btuh (in.)
50
18,000 3/4 .99
24,000 3/4 1
30,000 3/4 .98
3/4
.93
36,000
7/8 .98
3/4 .93
42,000
7/8 .97
1-1/8 1
3/4
.90
48,000
7/8 .96
1-1/8 1
7/8 .93
60,000
1-1/8 .99
NOTE: For a condenser with a liquid valve tube connection
less than 3/8" diameter, use 3/8" liquid line tubing for a line
set greater than 25 feet.
EQUIVALENT LINE LENGTH (FT)
75 100 125
.97 .96 .95
.99 .99 .98
.97 .96 .95
.90 .86 .83
.96 .94 .92
.90 .87 .83
.96 .94 .93
1 .99 .99
.86 .82 .78
.94 .93 .91
1 .99 .99
.91 .89 .86
.98 .98 .97
TABLE 5. LOSSES FROM SUCTION LINE ELBOWS
(EQUIVALENT LENGTH, FT.)
Type of elbow fitting
90° short radius
90° long radius
45°
Installation Requirements
1. In a completely horizontal installation with a long line
set where the evaporator is at the same altitude as
(or slightly below) the condenser, the line set should
be sloped towards the evaporator. This helps reduce
refrigerant migration to the condenser during a
system's off-cycle.
2. For a system installation where the evaporator is
above the condenser, an inverted vapor line trap
should be installed on the suction line just before the
inlet to the evaporator (see Fig 6). The top of the
inverted loop must be slightly above the top of the
evaporator coil and can be created simply by brazing
two 90° long radius elbows together, if a bending tool
is unavailable. Properly support and secure the
inverted loop to the nearest point on the indoor unit or
adjacent structure.
150
.95
.97
.94
.79
.90
Fig 6. Evaporator unit with inverted vapor loop
.80
.92
.98
3. An oil trap is required at the evaporator only if the
N/R
.89 condenser is above the evaporator. Preformed oil
.98
traps are available at most HVAC supply houses, or oil
.84
traps may be created by brazing tubing elbows together
.97
(see diagram below). Remember to add the equivalent
length from oil traps to the equivalent length calculation
of the suction line. For example, if you construct an oil
trap using two 45° elbows, one short and one long 90°
elbow in a ¾" diameter suction line, the additional
equivalent length would be 0.7+ 0.7+1.7+1.5, which
equals 4.6 feet (refer to table 2).
I.D. (in.)
3/4 7/8 1-1/8
1.7 2 2.3
1.5 1.7 1.6
0.7 0.8 1
59