12
INSTALLATION
Interconnecting Tubing (cont�)
Interconnecting Tubing and
Fitting Losses
Refrigerant tubing is measured in terms of actual
length and equivalent length� Actual length is used
for refrigerant charge applications� Equivalent
length takes into account pressure losses from
tubing length, fittings, vertical separation, acces-
sories, and filter dryers. The table below references
different commonly used equivalent lengths.
Equivalent Length for Fings ()
Line Size
(in)
90° Short
Radius
Elbow
90° Long
Radius
Elbow
45°
Elbow
Solenoid
Valve
Check
Valve
Site
Glass
Filter
Dryer
3/8
1.3
0.8
0.3
6
4
0.4
6
1/2
1.4
0.9
0.4
9
5
0.6
6
5/8
1.5
1
0.5
12
6
0.8
6
3/4
1.9
1.3
0.6
14
7
0.9
6
7/8
2.3
1.5
0.7
15
8
1
6
1-1/8
2.7
1.8
0.9
22
12
1.5
6
Liquid Line Selection
The purpose of the liquid line is to transport warm
sub-cooled liquid refrigerant from the outdoor unit
to the indoor unit� It is important not to allow the
refrigerant to flash any superheated vapor prior
to the expansion device of the indoor coil� The
flashing of refrigerant can occur for the following
reasons:
• Low refrigerant charge
• Improperly selected liquid line size
• Absorption of heat prior to expansion device
• Excessive vertical rise between the condenser
and evaporator
Table 2 lists the equivalent length per 25’ of liquid
line at various diameters up to 300’� The total pres-
sure drop allowed for the liquid line is 50 PSI� The
procedure for selecting the proper liquid line is as
follows:
• Measure the total amount of vertical rise
• Measure the total amount of liquid line needed
• Add all of the equivalent lengths associated with
any fittings or accessories using the table above.
• Add the total length and fitting pressure drop.
This will equal your total equivalent length�
• Round-down the total equivalent length to the
closest value in Table 2�
• Reference Table 2 to verify the round-down val-
ue of the calculated equivalent length is compat-
ible with the required vertical rise and diameter
of liquid line�
Table 1
Note: Elevaon is defined as the
highest point of the line set to the
lowest
Figure 1
Tubing
