195 Rev. 3
SERVICING
The maximum recommended length of tubing to be used with
a remote cooling system is 50 feet; this includes a minimum
of turns with a maximum permissible rise of 20 feet for the
liquid line.
1. All horizontal suction line runs must be pitched towards
the compressor (one inch per ten feet). This aids the
return of the oil to the compressor.
2. Avoid long running traps in horizontal suction line.
3. The liquid line must not be attached to an uninsulated
suction line.
4. If the liquid line is routed through an area which has an
ambient higher than 120°F., then that portion of the liquid
line has to be insulated.
5. Suction line sizes should allow for sufficient internal line
velocity (approximately 1500 FPM) to return oil to the
compressor. An oil trap by the indoor coil is necessary
to aid in oil return when the outdoor unit is located above
the indoor coil.
6. Special precautions must be taken into consideration for
liquid line sizing where the indoor coil is above the out-
door unit to prevent flash gas at the entrance of the me-
tering device. (See Liquid Line size and maximum rise
chart).
7. In sizing refrigeration piping determine the number of 90°
and 45° elbows required and add their equivalent lengths
to the length of straight pipe. Find the equivalent length
of fittings in the following table:
EQUIVALENT LENGTH IN FEET
SUCTION LINE ELBOWS
Fitting Size
I.D. Inches
Sweat, Copper
3/8
1/2
5/8
3/4
7/8
1 1/8
90° Short Radius
1.2
1.4
1.5
1.7
2.0
2.3
90° Long Radius
0.8
0.9
1.0
1.5
1.7
1.8
45°
0.4
0.5
0.6
0.7
0.8
1.0
NOTE: The outdoor unit's refrigerant holding charge is for the
indoor coil plus 25 feet of liquid line. If the piping run is longer
than 25 feet, additional refrigerant must be added per the
Refrigerant Correction Chart.
EXAMPLE: One 7/8" 90° short radius copper sweat ell is
equal to the resistance of two foot of 7/8" O.D. straight pipe.
To obtain the total equivalent length, add length of straight
pipe to equivalent length of fittings.
REFRIGERANT LINES IN EXCESS OF 50 FEET
It is always best to keep refrigerant lines to 30 feet or less,
however this is not always possible. The following informa-
tion should be used to size refrigerant lines in excess of 50
feet.
1. Sketch the system and determine the number of traps
required. Traps are required only if the condensing unit is
above the evaporator coil. Traps are only necessary in
the suction line.
SUCTION LINE TRAPS
CONDENSER UNIT ABOVE EVAPORATOR
VERTICAL LIFT (FEET)
TRAPS REQUIRED
0 - 5
0
6 - 19
1
20 - 39
2
40 - 59
3
The first trap goes at the outlet of the evaporator coil. The
remaining traps go halfway up the riser (2 traps total), or 1/3
and 2/3 the way up the riser (3 traps total).
2. Estimate the effective length of pipe. Remember, each
trap will have a substantial equivalent length. The suc-
tion line effective length could therefore be considerably
greater than the liquid line effective length.
3. Size the suction line per the Suction Line Sizing Chart.
SUCTION LINE SIZING
EFFECTIVE
LENGTH
50
75
100
125
150
18
5/8
5/8
3/4
3/4
3/4
24
5/8
3/4
3/4
3/4*
-
30
3/4
7/8
7/8
7/8
7/8
36
3/4
7/8
7/8
7/8*
-
42
7/8
7/8
7/8*
-
-
48
7/8
1 1/8
1 1/8
1 1/8
1 1/8
60
1 1/8
1 1/8
1 1/8
1 1/8
-
*Use size shown for vertical portion of run. Use next size
larger for horizontal portion of the run.
4. Size the liquid line per the following Liquid Line Sizing
charts. If the evaporator coil is above the condensing
unit, the chart will show the maximum permissible verti-
cal lift, and liquid line combination for that unit. Be sure to
use the proper chart.
