A
CU MANUAL
IOM-14
17 of 46
Feb 06 R4
PIPE SELECTION PROCEDURE
NOTE:
Distances shown on piping selection tables are for EQUIVALENT LENGTH. Equivalent length is
the actual distance PLUS allowance for fittings. Typically fittings will increase the “actual
length” by 50% to 100%.
1.
Record the actual distance the piping must be run to connect the components. Refer to Submittal
Record for maximum allowed line length. If exceeded, please contact an Engineered Air office.
2.
Determine the number of fittings required. Include all fittings required for traps etc.
3.
Estimate an equivalent length by doubling the actual length of tubing.
4.
Select a preliminary tubing size from Table 2.
5.
Lookup the equivalent length of the fittings for this tubing size from Table 1.
6.
Add the equivalent length of the fittings to the actual length of tubing to calculate the total
equivalent length of the tubing.
7.
If the calculated length is substantially different from the estimated length (item 3) Reselect the
tubing size from Table 2. Use this value and repeat steps 5, 6 and 7.
Example:
A CU-212 with two 10.5-ton circuits is to be installed on a mall. Each circuit has 25 feet of horizontal run,
10-feet of vertical rise, 15 elbows and an angle service valve. Select a suction line and a liquid line for
each circuit.
Solution:
The capacity of each circuit is 10.5 tons.
Suction line selection
1.
The system has 35 feet of actual piping run.
2.
An initial estimate would be 70 feet of equivalent length (2 x 35ft.).
3.
From Table 2 (R407c), select the closest length for the selection. (50 feet). Choose 1 3/8” tubing
(10 ton 50 feet Equivalent length).
4.
Number of fittings is given at 15 elbows, 1 angle valve
5.
From Table 1 determine equivalent length (EL) of fittings.
+ (15) long radius elbows at EL = 2.3 ft. each
+ (1) angle valve EL = 15 ft. each
6.
Calculate equivalent length.
35 feet (15 x 2.3 = 34.5 feet elbows) + (15 ft angle valve) = 84.5 feet.
7.
This length is closer to 100 feet than the original 50 feet used for the first estimate. RESELECT from
table 2 (R407c). Using 100 Feet equivalent length.
8.
Reselect at 100 feet. Choose 1 5/8 …new EL = (35 + (15 x 2.6) + 18) = 92 feet. (This is closer to the
100 feet the table used.)
9.
Use:
1 5/8” tubing for the suction line.
Liquid line selection
1.
Estimate 70 feet of EL; Select 5/8” from table 1. (the closest length is 50’) Calculate actual EL = 35 ft +
(15 x 1.0) + 7 ft. = 57 feet actual equivalent length. This is close to the length initially estimated.
2.
Check the 100-foot column, the tube size is the same.
3.
Use:
5/8” for liquid.
The piping selections for this CUB-212 example would be:
