90
Chapter 5
B. R-22 Refrigerant Line Sizes for Remote
Systems Air Conditioning and Heat
Pumps
Condensers and evaporators should be designed and
circuited to maintain adequate velocity to prevent
oil trapping.
The tube sizes suggested below are for connecting
lines of remote systems. The basis for selection is to
maintain adequate velocity which assures oil return
to the compressor, an acceptable pressure drop to
assure compressor capacity and minimum tubing
cost.
To assure adequate oil return, suction line velocities
should be minimum of 750 fpm for horizontal or
down flow and 1500 fpm for up flow. Gas velocities
of 3000 fpm or more will create noise problems and
should be avoided.
Where a choice of line sizes is possible because of the
overlap in the compressor capacity table, the larger
sized lines are suggested to minimize the system
pressure drop.
Consider these installation notes:
•
Suction line sizes (up flow) provide adequate
gas velocities to assure oil return to the com-
pressor and, therefore, remain constant in size
regardless of the vertical lift. Suction line traps
are not required. Horizontal suction lines are
sized larger to reduce pressure drop.
•
Suction line lengths in excess of 100’ are not
recommended.
•
On heat pump systems, the lines serving as
both a discharge line and suction line, should
be sized as a suction line.
•
Liquid line sizes are based on pressure drops
that will not permit gas formation for horizon-
tal lengths up to 100’.
The recommendations shown in Table 5-3 are based
on the use of standard refrigeration grade tubing
and do not include considerations for additional
pressure drop due to elbows, valves, or reduced joint
sizes.
Table 5-3: R-22 Refrigerant Line Sizes for Remote Systems Air Conditioning and Heat Pumps
SUCTION LINE OUTER DIAMETER
Nominal Compressor
Cooling Capacity
(BTU/Hr.)
Vertical Up
Flow
Vertical
Down Flow
or
Horizontal
Liquid Line
Outer
Diameter
Discharge Line Length &
Outer Diameter
25’
50’
100’
1500 FPM
2500 FPM
5700
9400
3/8
1/2
1/4
5/16
5/16
3/8
8000
13000
1/2
1/2
1/4
5/16
3/8
3/8
11200
18500
1/2
5/8
5/16
3/8
3/8
1/2
17000
30000
5/8
3/4
5/16
3/8
1/2
1/2
27000
44000
3/4
7/8
3/8
3/8
1/2
5/8
38000
51000
7/8
1 1/8
3/8
1/2
5/8
5/8
38000
67000
7/8
1 1/8
1/2
1/2
5/8
5/8
60000
102000
1 1/8
1 3/8
1/2
5/8
3/4
3/4
96000
156000
1 3/8
1 5/8
5/8
3/4
3/4
7/8
144000
228000
1 5/8
2 1/8
5/8
3/4
7/8
1 1/8