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LIMITS / PLACEMENT
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Piping Limitations and Placement Considerations
The following is an example of manual pipe size calculations. Designers are highly encouraged to use LATS instead of manual calculations.
Pipe Sizing
REFRIGERANT PIPING DESIGN
1
For calculation purposes, assume equivalent pipe length of Y-branch is 1.6 feet, and equivalent pipe length of header is 3.3 feet.
Length
Total pipe length
Longest actual pipe length
Longest Equivalent pipe length
1
A + ΣB + ΣC + D ≤475.7 feet
A + B + D ≤230 feet
A + B + D ≤295.2 feet
ℓ
Longest pipe length after first branch
B + D ≤ 131 feet
Elevation1
Elevation differential (Water source unit ↔ Indoor unit)
≤ 98.4 feet
Elevation2
Elevation differential (Indoor unit ↔ Indoor unit)
≤ 49 feet
Distance between fittings and indoor units
≥20 inches
Distance between fittings and
Y-branches
≥20 inches
Distance between two Y-branches
≥20 inches
Distance between Header and indoor units
≥20 inches
Table 29: Pipe Capabilities.
Example: Five (5) indoor units connected
Water Source Units (WSU).
IDU: Indoor Units.
Y-branches.
Header.
A: Main Pipe from First Y-branch.
B: Pipe from Y-branch to Y-branch or Header.
C: Pipe from Y-branch or Header to Indoor Unit.
D: Pipe to Farthest Indoor Unit.
Water Mini System Using Y-branches and Header
Length: ≤230 feet
ℓ: ≤131 feet
Elevation1: ≤98.4 feet
Elevation2: ≤49 feet
Water Source Unit
Header
First Y-branch
Second Y-branch
B
Brazed Cap
IDU
IDU
C
D
C
C
C
IDU
IDU
Y-branch
To Water
Source
Unit
To Indoor
Units
IDU
Downstream Total Capacity of Indoor Units (Btu/h)
Liquid Pipe (Inches O.D.)
Vapor Pipe (Inches O.D.)
≤19,100
Ø1/4
Ø1/2
< 54,600
Ø3/8
Ø5/8
≤76,400
Ø3/8
Ø3/4
Table 30: Refrigerant Pipe Diameter (B) from Y-branch to Y-branch / Header.
• Indoor units must be installed at a lower position
than the Header.
• Y-branch pipes cannot be used after Headers.
• Install the Header so that the pipe distances
between the between the connected indoor
units are minimized. Large differences in pipe
distances can cause indoor unit performances
to fluctuate.
• Always reference the LATS software report.
•
Connection piping from branch to branch cannot exceed the main pipe diameter (A) used by the water source unit.
• Y-branches and other header branches cannot be installed downstream of the initial header branch.