Long Lineset Instructions

Page 27
TWO 90° ELBOWS INSTALLED IN LINE SET
WILL REDUCE LINE SET VIBRATION.
INSTALL UNIT AWAY FROM
WINDOWS
Figure 21. Outside Unit Placement
COMPLEX LIQUID LINE SIZING
Example 1 – Liquid Sizing with Multiple Evaporators
Occasionally, more than one evaporator may be connected
to one condensing unit. The line sizing method shown here
is for a system with multiple evaporators operating
simultaneously.
In this example, all the evaporators are located above the
condensing unit. All evaporators experience the effects of
liquid lift. The system is equipped with a 2-ton, 5-ton and
3-ton evaporator in order from top to bottom.
Figure 22. Liquid Plumbing
Given: Ten ton commercial (single stage) condensing unit
on ground with three evaporators above condenser. See
figure 22.
Find: Select tube size from figure 8.
Solution: Size each segment based on the tons of
refrigerant that will flow in the segment.
Segment A to B
First solve segment A to B (10 tons). Figure 8 indicates that,
for a 10-ton system, 5/8 inch outside diameter. Liquid line
should be selected (smallest liquid line with acceptable
velocity). Figure 4 also indicates that 5/8 inch line carrying
10 tons of capacity has 4.3 psi drop per 100 feet. Then
determine the equivalent length of the segment to calculate
the pressure drop.
Twenty one feet of pipe, plus three 90 elbows (one
equivalent foot each, from table 4), plus one tee (line side of
tee at 0.8 equivalent feet each, from table 4) = 24.8
equivalent feet length (round up to 25 equivalent feet).
When we multiply 4.3/100 by 25 equivalent feet, we see
that the total friction loss is 1.1 psi.
Now, we must add the pressure drop for vertical lift.
HCFC-22 pressure drop is 1/2 psi per foot of vertical lift.
When multiplied by 10 feet vertical lift we find that pressure
drop due to lift = five psi.
When the two components of pressure drop are added
together we find that the total pressure drop in this 5/8 inch
line = 6.1 psi.
Segment B to C
B to C has a capacity of three tons. Figure 4 indicates a
three ton system should use 3/8 inch outside diameter. line
(smallest line with acceptable velocity). Now, determine the
equivalent length of the segment to calculate the pressure
drop.
Two feet of pipe, plus one tee (branch side of tee at 1.5
equivalent feet each) = 3.5 equivalent feet length (round up
to four equivalent feet).
From figure 4, 3/8 inch outside diameter. liquid line with
three tons capacity has 8.3 psi drop per 100 feet. When we
multiply 8.3/100 by four equivalent feet, we see that the
total friction loss is 0.33 psi.
Vertical lift = 0.
In this segment, the only component of pressure drop is the
equivalent length; 0.33 psi.
Segment B to D
B to D has a capacity of seven tons. Select from figure 4 a
5/8 inch outside diameter. line (smallest line with
acceptable velocity). Then determine the equivalent length
of the segment to calculate the pressure drop.
10 feet of pipe, plus one tee (line side of tee at 0.8
equivalent feet) = 10.8 equivalent feet length (round up to
11 equivalent feet).