13
Tubing
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, fi ttings, vertical separation, acces-
sories, and fi lter dryers. The table below references
diff erent 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 fl ash any superheated vapor prior
to the expansion device of the indoor coil. The
fl ashing 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 fi ttings or accessories using the table above.
• Add the total length and fi tting 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 rounded-down
value of the calculated equivalent length is com-
patible with the required vertical rise and diam-
eter of liquid line.
Table 1
Note: Elevaon is defined as the
highest point of the line set to the
lowest
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