Engineering Manual
Design Guideline Summary
Example: LMU540HV outdoor unit with
seven (7) indoor units, and two (2)
branch distribution units connected.
ODU: Outdoor Unit.
IDU: Indoor Unit.
BD: Branch Distribution Unit(s).
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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
IDU
B
B
B
B
B
B
Table 101: Multi F MAX Outdoor Unit Refrigerant Piping System Limitations.
Pipe Length
(ELF = Equivalent
Length of pipe in Feet)
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Main pipe (Outdoor Unit to
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Minimum
10 feet
Maximum
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Branch pipe (Branch Distribu-
tion Units to Indoor Units: B)
Minimum
10 feet
Maximum
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Elevation Differential
(All Elevation
Limitations are
Measured in Actual
Feet)
If outdoor unit is above or below indoor unit (h1)
IHHW
Between the farthest two indoor units (h2)
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Between branch distribution unit and farthest
connected indoor unit(s) (h3)
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Between branch distribution units (h4)
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Table 102: Multi F MAX 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
Example: LMU540HV outdoor unit with
four (4) indoor units, and one (1) branch
distribution unit connected.
ODU: Outdoor Unit.
IDU: Indoor Unit.
BDU: Branch Distribution Unit.
A: Main Pipe.
B: Branch Pipe (Branch Distribution Unit to
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A
h2 ≤ 49.2 feet
h3 ≤ 32.8 feet
h1 ≤ 98.4 feet
BDU
ODU
IDU
IDU
IDU
IDU
B
B
B
B
Multi F MAX System with One Branch Distribution Unit
Multi F MAX System with Two Branch Distribution Units
The following are examples of manual pipe size calculations. Designers are highly encouraged to use LATS for Multi F systems.
REFRIGERANT PIPING DESIGN
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DESIGN & PRACTICES | 189
Refrigerant Piping Design and Best Practices
MULTI
F
MAX
MULTI
F