90 | LIMITS / PLACEMENT
MULTI V 5 Outdoor Unit Engineering Manual
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PIPING LIMITATIONS
For Systems Designed for Heat Pump Operation
Following pages present Multi V 5 piping limitations and are for illustrative purposes only. Designers MUST use LATS when designing LG VRF systems.
1
For the first branch pipe, use the branch pipe that matches main pipe A diameter.
Downstream Total Capacity of IDUs (Btu/h)
Liquid pipe (inches OD) Vapor pipe (inches OD)
1/4Ø 1/2Ø
3/8Ø 5/8Ø
3/8Ø 3/4Ø
3/8Ø 7/8Ø
1/2Ø 1-1/8Ø
5/8Ø 1-1/8Ø
5/8Ø 1-3/8Ø
3/4Ø 1-3/8Ø
3/4Ø 1-5/8Ø
Table 22: Pipe Diameters (B) from Y-branch to Y-branch / Header.
If the pipe (B) diameters after the first branch are bigger than the main pipe (A) diameters, pipe (B) must changed to match main pipe (A)
sizes.
Example: When an indoor unit combination ratio of 120% is connected to a 22-ton outdoor unit:
Outdoor unit main pipe (A) diameters: 1-3/8Ø inches (vapor) and 5/8Ø inches (liquid).
1. Pipe (B) diameters: 1-3/8Ø (vapor) and 3/4Ø (liquid) (after the first branch, when indoor unit combination ratio is 120% [26 tons]).
2. After the first branch, pipe (B) diameters must be changed to 1-3/8Ø inches (vapor) and 5/8Ø inches (liquid) to match main pipe (A)
sizes.
Instead of using the total indoor unit capacity to choose main pipe (A) diameters, use outdoor unit capacity to choose downstream main pipe
(A) diameters.
Do not permit connection pipes (B) from branch to branch to exceed main pipe (A) diameters as indicated by outdoor unit
capacity. Example: When an indoor unit combination ratio of 120% is connected to a 20-ton outdoor unit (24 tons), and indoor unit with a
7,000 Btu/h capacity is located at the first branch:
1. Main pipe (A) diameters on a 20-ton outdoor unit: 1-1/8Ø inches (vapor) and 5/8Ø inches (liquid).
2. Pipe diameters between first and second branches, however, are: 1-3/8Ø (vapor) and 3/4Ø (liquid) (connected downstream indoor unit
capacity is 20 tons).
3. If main pipe (A) diameters of a 20-ton outdoor unit are 1-1/8Ø (vapor) and 5/8Ø (liquid), then the pipe diameters between the first and
second branches must be changed to match.
Conditional Applications
Conditional applications are computed in LATS. See below for an explanation of when pipes are upsized.
If the equivalent length between the first Y-branch to the farthest indoor unit is >131 feet (up to 295 feet maximum):
• Pipe segment diameters between the first Y-branch and the second Y-branch must be sized up by one. This applies to both liquid and vapor
pipes. If the next size up is not available, or if the piping segment diameters are the same as main pipe (A) diameters, sizing up is not
possible.
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feet.
Indoor Unit Capacity
1
Liquid pipe (inches OD) Vapor pipe (inches OD)
1/4Ø 1/2Ø
3/8Ø 5/8Ø
3/8Ø 3/4Ø
Table 23: Indoor Unit Connecting Pipe from Branch (C).
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 (vapor).
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