Section 5. Calculations - Tubing Equivalent Length, Tube Size And Refrigerant - Daikin RR20AVAK9 Installation & Service Reference

SECTION 5. CALCULATIONS - TUBING EQUIVALENT LENGTH, TUBE SIZE AND REFRIGERANT

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. Add the total straight (lineal) length of tubing to the
equivalent length of elbows and bends to get total equivalent length.
Equivalent length = Length
2. Table 5-1 lists the equivalent length gained from adding bends to the suction line. Properly size the suction line to
minimize capacity loss.
Table 5-1. Losses from suction line elbows (equivalent length, ft.)
EXAMPLE: 3/4" suction line using 3/4" elbows
150 feet of straight tubing + (four short radius elbows x1.7) + (2 long radius elbows x1.5) =
150 + 3.4 + 3 = 156.4 equivalent feet
3. Table 5-2 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.
NOTE: Select the proper suction tube size based on equivalent length of the suction line
(see Tables 5-1 and 5-2) and recalculated system capacity.
Horizontal
Type of
Elbow Fitting
90° short radius
90° long radius
45°
Table 5-1. Losses from suction line elbows (equivalent length, ft.)
Type of Elbow
Fitting
90 ° short radius
90 ° long radius
45°
Table 5-2. Losses from suction line elbows (equivalent length, m)
+ Length + Losses from bends (see Table 5-1)
Vertical
Inside Diameter (in)
3/4 7/8 1 1/8
1.7 2 2.3
1.5 1.7 1.6
0.7 0.8
Inside Diameter (in)
3/4 7/8 1 1/8
0.5 0.6
0.5 0.5
0.2 0.2
32
1
0.7
0.5
0.3