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Design Guideline Summary
The following are examples of manual pipe size calculations. Designers are highly encouraged to use LATS for Multi F systems.
REFRIGERANT PIPING DESIGN
B
A
h2 ≤ 49.2 feet
A
h3 ≤ 32.8 feet
h4 ≤ 49.2 feet
h1 ≤ 98.4 feet
BDU Y-Branch
BDU
IDU
A
ODU
IDU
IDU
IDU
IDU
IDU
B
B
B
B
B
Multi F MAX with LGRED System with Two Branch Distribution Units
Example: LMU420HHV outdoor unit with
six (6) indoor units and two (2) branch
distribution units connected.
ODU: Outdoor Unit.
IDU: Indoor Unit.
BDU: Branch Distribution Unit(s).
ΣA: Main Pipe.
ΣB: Branch Pipe (Branch Distribution Unit[s] to
Indoor Unit[s]).
Table 127: Multi F MAX with LGRED Outdoor Unit Refrigerant Piping System Limitations.
Pipe Length
(ELF = Equivalent
Length of pipe in Feet)
Total piping length (ΣA + ΣB)
≤475.7 feet
Main pipe (Outdoor Unit to
Branch Distribution Units: ΣA)
Minimum
10 feet
Maximum
≤180.4 feet
Total branch piping length (ΣB)
≤295.3 feet
Branch pipe (Branch Distribu-
tion Units to Indoor Units: B)
Minimum
10 feet
Maximum
≤49.2 feet
Elevation Differential
(All Elevation
Limitations are
Measured in Actual
Feet)
If outdoor unit is above or below indoor unit (h1)
≤98.4 feet
Between the farthest two indoor units (h2)
≤49.2 feet
Between branch distribution unit and farthest
connected indoor unit(s) (h3)
≤32.8 feet
Between branch distribution units (h4)
≤49.2 feet
Table 128: Multi F MAX with LGRED Piping Sizes.
Piping
Main Pipe A
(inch)
Branch Pipe B
Liquid Ø3/8
Depends on the size
of the indoor unit piping
Gas Ø3/4
Due to our policy of continuous product innovation, some specications may change without notication.
©LG Electronics U.S.A., Inc., Englewood Cliffs, NJ. All rights reserved. “LG” is a registered trademark of LG Corp.
DESIGN & PRACTICES | 223
Refrigerant Piping Design and Best Practices
MULTI
F
MAX
MULTI
F
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