Pipe Layout Procedure - LG Multi V mini Engineering Manual

Creating a Balanced Piping System
Balancing dampers, ball valves, orifices, circuit setters, or other
flow control devices cannot be used to modify or balance the flow of
refrigerant in a VRF piping system. Therefore, variable refrigerant
flow systems must be designed to be "self balanced." Pipe sizing
considerations include pipe length, pipe segment pressure drop
relative to other pipe segments in the system, type and quantity of
elbows, bends present, fitting installation orientation, and indoor
unit elevation differences. Balanced liquid refrigerant distribution is
solely dependent on the designer choosing the correct pipe size for
each segment.
It is imperative the designer avoids creating excessive pressure
drop. In the liquid line, the pipe system must be designed in a
manner that avoids the creation of unwanted vapor. When liquid re-
frigerant is subjected to excessive pressure drop, the refrigerant will
change state and "flash" to vapor. If vapor bubbles form in a stream
of liquid refrigerant before reaching the electronic expansion valve
(EEV), loss of system temperature control and EEV valve damage
may occur.
Handling Field Piping Changes
Any field changes, such as rerouting, shortening or lengthening a
pipe segment, adding or eliminating elbows and/or fittings, re-sizing,
adding, or eliminating indoor units, changing the mounting height, or
moving the location of a device or fitting during installation should be
done with caution and always verified in LATS Multi V before piping
supplies are purchased or installed. Doing so may have a positive
effect on job profit, eliminate rework, and may avoid unexpected
necessary pipe changes before commissioning.
Layout Procedure
When this procedure is complete, the liquid line working drawing
should contain the information for each pipe segment and others
entities depicted in Figure 35 on page 65.
1. Choose the location of the indoor units and draw them on the
building drawing.
2. Choose the location of all Y-Branch and Header fittings and add
them to the drawings. Verify that all fittings are positioned per
the guideline limitations set forth in "Y-Branch Kits" on page 66
and "Header Kits" on page 67.
3. Plan the route for interconnecting piping. Draw a one-line depic-
tion of the pipe route chosen on the building drawings.
4. Calculate the actual length of each pipe segment and note it on
the drawing next to each segment.
5. Using the data obtained while selecting the system components
from the "Equipment Selection Procedure" on page 51, list
the nominal cooling capacity next to each indoor unit on the
drawing.
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PIPE LAYOUT PROCEDURE

6. Starting at the runout segment servicing the indoor unit located
farthest from the outdoor unit, note the connected nominal
capacity of the indoor unit served by the pipe segment. Record
these values next to each segment on the drawing.
7. At the branch or pipe segment upstream of the farthest Y-Branch
or Header fitting from the outdoor unit, note the downstream
connected nominal capacity of all indoor units served by the
pipe segment. Record these values next to the segment on the
drawing. Repeat the same procedure for each branch and main
pipe segment woking your way up the liquid line back toward the
outdoor unit for each leg of the piping system. When completed,
all segments will be noted with the nominal capacity of the
downstream indoor units served by each segment.
8. Use Table 24 to select the correct pipe size for both the liquid
and vapor lines. Note the chosen line sizes next to each seg-
ment.
9. Size Y-Branch and Header fittings. Refer to Cut-Sheets for "Y-
Branch Kits" on page 4 and "Header Kits" on page 5 to determine
the part number of each LG Y-Branch and/or Header based on
the connected downstream nominal capacity served. Record
the part number next to each fitting.
10. Calculate the equivalent pipe length in feet of the branch and
main pipe segments. Y-Branch and Header equivalent lengths
should be included with the upstream segment only. Use
equivalent pipe length data provided with purchased fittings. If
unavailable, use the data provided in Table 24. Y-Branch and
Header equivalent lengths are found in the Cut-Sheets on pages
4 and 85. Equivalent length values will be used to calculate the
system refrigerant charge.
11. Verify the actual and/or equivalent pipe length complies with the
limitations listed in Table 23. If the limitations are exceeded, ei-
ther reroute the pipe or change the location of selected Y-Branch
fittings, Header fittings, and/or indoor unit locations so the design
conforms with all limitations.
12. Verify the manually sized pipe design is acceptable using LATS
Multi V. Using the LATS tree mode modeling option, enter the
actual pipe length of each pipe segment. Account for the ad-
ditional pressure drop created by elbows by double-clicking on
the segment length text in LATS Multi V. In the dialog box, enter
the elbow count.
13. After entering all necessary information into LATS, click on the
"Auto Pipe" button on the left followed by the "System Check"
button located under the "Auto Pipe" button. If no dialog boxes
pop up indicating an error and none of the entities on the tree
mode diagram have a red box around or along them, the pipe
design is acceptable and the layout work is complete. If errors
were indicated, modify the pipe design as needed. For assis-
tance, contact the applied product representative in your area.
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SYSTEM ENGINEERING
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