51
RTAA-IOM-3
Table 4
Liquid Line Size for Horizontal and/or Downflow Lines
Circuit Size: Liquid Line Size (OD”)
Total Equiv. Length (Ft) 100 Ton 85 Ton 70 Ton
25' 1 1/8 1 1/8 1 1/8
50' 1 3/8 1 1/8 1 1/8
75' 1 3/8 1 3/8 1 3/8
100' 1 3/8 1 3/8 1 3/8
125' 1 3/8 1 3/8 1 3/8
150' 1 5/8 1 3/8 1 3/8
175' 1 5/8 1 5/8 1 5/8
200' 1 5/8 1 5/8 1 5/8
225' 1 5/8 1 5/8 1 5/8
250' 1 5/8 1 5/8 1 5/8
275' 1 5/8 1 5/8 1 5/8
300': 1 5/8 1 5/8 1 5/8
Table 5
Equivalent Lengths of Non-Ferrous valves and Fittings
Line Size Globe Angle Short Long
Inches OD Valve Valve Radius ELL Radius ELL
1 1/8 87 29 2.7 1.9
1 3/8 102 33 3.2 2.2
1 5 /8 115 34 3.8 2.6
2 1/8 141 39 5.2 3.4
2 5/8 159 44 6.5 4.2
3 1/8 185 53 8.0 5.1
3 5/8 216 66 10.0 6.3
4 1/8 248 76 12.0 7.3
Reproduced by permission of Air conditioning and Refrigeration Institute.
Line Sizing
Equivalent Line Length
To determine the appropriate size for
field installed liquid and suction lines, it
is first necessary to establish the
equivalent length of pipe for each line.
An initial approximation can be made
by assuming that the equivalent length
of pipe is 1.5 times the actual length of
pipe. These assumed lengths can then
be used with the appropriate tables in
the Liquid Line Sizing section and the
Suction Line Sizing sections which
follow.
It is also necessary to know the
capacity (tons) of each circuit. Circuit
capacities for each RTAA unit are listed
in Table 3.
The following are examples of how to
determine line sizes.
Liquid Line Sizing
This example uses the unit installation
shown in Figure 31 and assumes an 85
ton circuit. The actual length of field
installed piping is 117 feet (80 + 8 + 8 +
21). Using the factor of 1.5, the
equivalent line length is 175 feet.
From Table 4, for horizontal and/or
downflow liquid lines, and assuming
an 85 ton circuit, 175 feet of equivalent
line requires a liquid line with an OD of
1 5/8 in.
There are 6 long-radius elbows in this
example. Using Table 5 and the pipe
OD of 1 5/8 in., these fittings represent
15.6 feet (6 elbows @ 2.6 feet each).
Therefore our new equivalent line
length is 132.6 feet (117 +15.6).
Referring back to Table 4, an 85 ton
circuit with 132.6 feet of equivalent pipe
length (use the dimension closest to
the calculated dimension) can use a
pipe O.D. of 1% in. rather than 1 5/8 in.
From Table 5 we see that the 6 elbows
of 1 3/8 in. have an equivalent pipe
length of 13.2 feet (6 elbows @ 2.2 feet
each). This further reduces the
equivalent pipe length to 130.2 feet
(117 + 13.2), and, as shown in Table 4,
still allows the use of 1 3/8 in. O.D. pipe.
Table 3
RTAA Circuit Capacities
Model Circuit 1 Circuit 2
130 70 70
140 70 70
155 85 70
170 100 70
185 100 85
200 100 100
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