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MULTI V Water IV System Installation Manual
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Pipe Sizing for Heat Recovery ARWB Series
Downstream IDU total capacity (Btu/h) Liquid pipe (in. OD)
Vapor pipe (in. OD)
Low pressure High pressure
≤19,100 1/4 1/2 3/8
<54,600 3/8 5/8 1/2
<76,400 3/8 3/4 5/8
<114,700 3/8 7/8 3/4
<172,000 1/2 1-1/8 7/8
<229,400 5/8 1-1/8 7/8
<248.500 5/8 1-3/8 1-1/8
<344,000 3/4 1-3/8 1-1/8
<592,500 3/4 1-5/8 1-3/8
Table 54: Refrigerant Pipe (B) Diameter between Y-branches and Y-branches / Heat Recovery Unit / Headers.
Table 55: 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 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 (maximum 295 feet):
• Pipe segment diameters between the first branch and the last branch should be sized up by one following the information in Table 49.
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.
• While calculating total refrigerant piping length, pipe (B) segment lengths between the first Y-branch and second Y-branch, and between
the second Y-branch and the heat recovery unit should be calculated by two.
• Length of pipe (C) from each indoor unit to the closest Y-branch, header, or heat recovery unit ≤131 feet.
• [Length of pipe from water source unit to farthest indoor unit (A+B+C)] - [Length of pipe from water source unit to closest indoor unit
(A+B+C)] ≤131 feet.
Table 56: Pipe Capabilities.
Indoor Unit Capacity
1
Liquid pipe (in. OD) Vapor pipe (in. OD)
≤19,100 1/4 1/2
≤54,600 3/8 5/8
≤76,400 3/8 3/4
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).
REFRIGERANT PIPING INSTALLATION
The following is an example of manual pipe size calculations. Designers are highly encouraged to use LATS instead of manual calculations.
Total pipe length
Length: Longest actual pipe length
Equivalent pipe length
1
A + ΣB + ΣC ≤ 1,640 feet
≤656 feet
≤738 feet
ℓ: Longest pipe length after first branch
≤131 feet (295 feet conditional application)
Elevation 1: Elevation differential (Water Source Unit ↔ Indoor Unit)
Height ≤164 feet
Elevation 2: Elevation differential (Indoor Unit ↔ Indoor Unit) [IDUs connected
to separate HRUs which are parallel (Y-branch) connected]
Height ≤131 feet
Elevation 3: Elevation differential (Indoor Unit ↔ Connected HRU or
Series Connected HRU)
Height ≤49 feet
Elevation 4: Elevation differential (Indoor Unit ↔ Indoor Unit [connected to
same Heat Recovery Unit])
Height ≤49 feet
Elevation 5 Elevation differential (Highest WSUnit ↔ Lowest WSU)
Height ≤16 feet
Distance between WSU to WSU
≤33 feet
Distance between ttings and IDU
≥20 inches
Distance between ttings and Y-branches / Headers
≥20 inches
Distance between two Y-branches / Headers
≥20 inches
Elevation between two heat recovery units if installed with a Y-branch
≤49 feet
Height difference between two series-piped heat recovery units
≤16 feet
Maximum number of heat recovery units per system
16
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