Long Lineset Instructions

Page 29
Figure 24. Suction Plumbing for Multiple Indoor Coils
Find: Select tube size from figure 6.
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). Select from figure 5 a
1-3/8 inch outside diameter. line (smallest suction line with
acceptable velocity). Then determine the equivalent length
of the segment to calculate the pressure drop.
21 feet of pipe, plus three 90 elbows (2.4 equivalent feet
each), plus one tee (line side of tee at 1.8 equivalent feet
each) = 30 equivalent feet length.
From figure 6, 1-3/8 inch outside diameter. suction line with
10 tons capacity has 3.3 psi drop per 100 feet. When we
multiply 3.3/100 by 30 equivalent feet, we see that the total
friction loss is 0.99 psi.
Vertical lift or drop has no effect on pressure in a vapor line.
Segment B to C
B to C has a capacity of three tons. Select from figure 8 a ¾
inch outside diameter. line (smallest line with acceptable
velocity yet with minimum capacity loss). Note figure 8
shows that ¾ inch line has significant pressure drop per 100
feet when combined with 3-ton capacity. If segment B to C
were much longer, the pressure drop would significantly
reduce capacity and a larger (7/8 inch) line would have to
be selected.
Determine the equivalent length of the segment to calculate
the pressure drop.
Two feet of pipe, plus one tee (branch side of tee at 3.5
equivalent feet each), plus six ells (1.25 equivalent feet
each) = 13 equivalent feet length.
From figure 8, ¾ inch outside diameter. suction line with
three tons capacity has 8.5 psi drop per 100 feet. When we
multiply 8.5/100 by 13 equivalent feet, we see that the total
friction loss is 1.11 psi.
Segment B to D
B to D has a capacity of seven tons. Select from figure 8 a
1-1/8 inch outside diameter. line (smallest line with
acceptable velocity). Then determine the equivalent length
of the segment to calculate the pressure drop.
Ten feet of pipe, plus one tee (line side of tee at 1.5
equivalent feet each) = 11.5 equivalent feet length.
From figure 8, 1-1/8 inch outside diameter. suction line with
seven tons capacity has 5.2 psi drop per 100 feet. When we
multiply 5.2/100 by 11.5 equivalent feet, we see that the
total friction loss is 0.6 psi.
Segment D to E
D to E has a capacity of five tons. Select from figure 8 a
1-1/8 inch outside diameter. line (smallest line with
acceptable velocity). Then determine the equivalent length
of the segment to calculate the pressure drop.
Forty feet of pipe, plus one tee (branch side of tee at 4.5
equivalent feet each), plus six elbows (1.8 equivalent feet
each) = 55.3 equivalent feet length.
From figure 8, 1-1/8 inch outside diameter. suction line with
5 tons capacity has 2.8 psi drop per 100 feet. When we
multiply 2.8/100 by 44.5 equivalent feet, we see that the
total friction loss is 1.55 psi.
Segment D to F
D to F has a capacity of two tons. Select from figure 8 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.
12 feet of pipe, plus seven 90 elbow (1.3 equivalent feet
each) = 21.1 equivalent feet length.
From figure 8, 5/8 inch outside diameter. suction line with
two tons capacity has 12 psi drop per 100 feet. When we
multiply 12/100 by 21.1 equivalent feet, we see that the total
friction loss is 2.53 psi. Here also, the pressure drop and
resulting capacity loss are approaching significant levels.
It might be more appropriate to select ¾ inch line in order to
limit the losses. Equivalent length now equals 20.75 feet.
From figure 8, ¾ inch outside diameter. suction line with two
tons capacity has 4.2 psi drop per 100 feet. When we
multiply 4.2/100 by 20.75 equivalent feet, we see that the
total friction loss is only 0.87 psi.