LG Multi IV - Page 126

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MULTI V IV Outdoor Unit Engineering Manual
REFRIGERANT PIPING DESIGN
Piping Design Guideline Summary
Downstream IDU total capacity (Btu/h) Liquid pipe (inches OD)
Vapor pipe (inches OD)
Low pressure High pressure
 1/4Ø 1/2Ø 3/8Ø
<54,600 3/8Ø 5/8Ø 1/2Ø
<76,400 3/8Ø 3/4Ø 5/8Ø
<114,700 3/8Ø 7/8Ø 3/4Ø
<172,000 1/2Ø 1-1/8Ø 7/8Ø
<229,400 5/8Ø 1-1/8Ø 7/8Ø
<248.500 5/8Ø 1-3/8Ø 1-1/8Ø
<344,000 3/4Ø 1-3/8Ø 1-1/8Ø
<592,500 3/4Ø 1-5/8Ø 1-3/8Ø
Length
Total pipe length Longest actual pipe length Equivalent pipe length
1
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Longest pipe length after first branch
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Elevation1
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Elevation2
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Elevation3
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49 feet
Elevation4
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49 feet
height1
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Distance between Outdoor Unit to Outdoor Unit
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Distance between two Y-branches / Headers
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Height differential between two Heat Recovery Units if installed with a
Y-branch
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Height differential between two series-piped Heat Recovery Units
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Table 40: Refrigerant Pipe (B) Diameter between Y-branches and Y-branches / Heat Recovery Unit / Headers.
Table 41: Indoor Unit Connecting Pipe from Branch (C).
1
For calculation purposes, assume equivalent pipe length of Y-branches to be 1.6 feet, and the equivalent pipe length of headers to be 3.3 feet.
Conditional Applications
Conditional application is computed in LATS. See below for an explanation of when pipes are upsized.
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• Pipe segment diameters between the first branch and the last branch should be sized up by one. This applies to both liquid and low / high
vapor pipes. If the next size up is not available, or if the pipe segment diameters are the same as main pipe (A) diameters, sizing up is not
possible.
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Y-branch and the heat recovery unit should be calculated by two.
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• >/HQJWKRISLSHIURPRXWGRRUXQLWWRIDUWKHVWLQGRRUXQLW$%&@>/HQJWKRISLSHIURPRXWGRRUXQLWWRFORVHVWLQGRRUXQLW$%&@IHHW
Table 42: Pipe Capabilities.
Indoor Unit Capacity
1
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
9,600-24,200 Btu/h 4-way 3 feet x 3 feet Cassette and 15,400-24,200 Btu/h High Static Ducted IDUs have 3/8Ø (liquid) and 5/8Ø (vapor).
The following is an example of manual pipe size calculations. Designers are highly encouraged to use LATS instead of manual calculations.