LG Multi IV Engineering Manual page 122

REFRIGERANT PIPING DESIGN
Piping Design Guideline Summary
The following is an example of manual pipe size calculations. Designers are highly encouraged to use LATS instead of manual calculations.
Combination Y-branch Pipe and Header Pipe Sizing When Installing a Dual-
Frame System
Example: Five (5) indoor units connected
ODU: Outdoor Units.
IDU: Indoor Units.
A: Main Pipe from Outdoor Unit to First Y-branch.
B: Y-branch to Y-branch / Header.
C: Y-branch / Header to Indoor Unit.
• Larger-capacity outdoor units must be the master in a multi-
frame system.
• Single-compressor outdoor units (72,000 Btu/h capacity)
cannot be the master outdoor units in a multi-frame system.
• Master outdoor unit capacity must be greater than or equal
to the slave outdoor unit capacity.
• Y-branches and other header branches cannot be installed
downstream of the initial header branch.
See pages 122-123 for refrigerant pipe diameter and pipe
length tables.
Table 34: Main Pipe (A) Diameter from Outdoor Unit to First Y-branch / Header Branch.
Pipe diameter when pipe
length is <295 feet
ODU
(Standard)
Capacity
(ton)
Liquid pipe Vapor pipe
(inches OD) (inches OD)
6 3/8Ø 3/4Ø
8 3/8Ø 7/8Ø
10-12 1/2Ø 1-1/8Ø
12-14* 5/8Ø 1-1/8Ø
14-18 5/8Ø 1-1/8Ø
20 5/8Ø 1-3/8Ø
22-28 3/4Ø 1-3/8Ø
30-42 3/4Ø 1-5/8Ø
*ARUN145BTE4 / ARUN145DTE4 and ARUN169BTE4 / ARUN169DTE4 only.
Table 36: Indoor Unit Connecting Pipe from Branch (C).
Indoor Unit Capacity
1
9,600-24,200 Btu/h 4-way 3 feet x 3 feet Cassette and 15,400-24,200 Btu/h High Static Ducted indoor units have 3/8Ø (liquid) and 5/8Ø
1
(vapor).
122 |
Pipe diameter when pipe Pipe diameter when height
Liquid pipe Vapor pipe
(inches OD) (inches OD)
1/2Ø 7/8Ø
1/2Ø 1-1/8Ø
5/8Ø No Increase
3/4Ø 1-1/4Ø
3/4Ø 1-1/4Ø
3/4Ø No Increase
7/8Ø 1-1/2Ø
7/8Ø No Increase
Liquid pipe (inches OD)
1/4Ø
3/8Ø
3/8Ø
©
Slave ODU
Master ODU
A
Y-branch
(first)
B
Y-branch
(second)
is >164 feet
Liquid pipe Vapor pipe
(inches OD (inches OD)
1/2Ø No Increase
1/2Ø No Increase
5/8Ø No Increase
3/4Ø No Increase
3/4Ø No Increase
3/4Ø No Increase
7/8Ø No Increase
7/8Ø No Increase
Vapor pipe (inches OD)
1/2Ø
5/8Ø
3/4Ø
Y-branch
To
outdoor unit
Header
B
C C
IDU IDU
C
C
IDU
Table 35: Refrigerant Pipe Diameter (B) from
Y-branch to Y-branch / Header.
Downstream Total
Liquid pipe
Capacity of IDUs
(inches OD)
(Btu/h)
1
1/4Ø
3/8Ø
3/8Ø
3/8Ø
1/2Ø
5/8Ø
5/8Ø
3/4Ø
3/4Ø
1 For the first branch pipe, use the branch pipe that matches main
pipe A diameter.
To indoor units
Brazed Cap
C
IDU
IDU
Vapor pipe
(inches OD)
1/2Ø
5/8Ø
3/4Ø
7/8Ø
1-1/8Ø
1-1/8Ø
1-3/8Ø
1-3/8Ø
1-5/8Ø