
System Engineering
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SYSTEM ENGINEERING
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PIPING DESIGN GUIDE
Engineering for Future Indoor Units
Commissioning in Stages
Begin with the end in mind to avoid system downtime, unneces-
sary costs, and the replacement of installed pipe segments when
adding subsequent indoor units and/or changing the location or
size of existing units after the system is initially designed and com-
missioned. Complete the following at the same time the initially
installed portion of the system is complete:
• Placement decisions for all future indoor units
• Piping plan for future piping
• Sizing of future pipe segments
In these applications, the future pipe design must be verified using
LG’s LATS Multi V software to confirm the pipe design complies
with LG’s design limitations after all future indoor unit additions
and planned pipe system changes are made. Install isolation ball
valves on the liquid and vapor lines near the Y-Branch or Header
on each leg where the future run-out piping and unit will be con-
nected. If possible, avoid installing the pipe segment between the
ball valve and the location of the future indoor unit during the initial
phase of the project. Cap the future pipe segment 3 to 6 inches
from the ball valve discharge and open the valve before system
evacuation and charging. Close the valve after charging the
system. Doing so ensures that refrigeration oil will return to the
compressor sump and not be trapped in future-use pipe segments.
For example, refer to Figure 35 and review the drawing of the run-
out segment tagged R1. It is very important to verify the system’s
CR is at least 50% initially and that it does not exceed 130% after
all future indoor unit changes and/or additions are completed. See
"How to Determine the System Combination Ratio (CR)" on page
55 for more information . Verify the anticipated RUR is within the
limitations listed on page 55.
Using Elbows
Third-party elbows are allowed as long as they are designed for
use with R410A refrigerant. The designer and installer should
use a minimum number of fittings since they must consider the
pressure drop each creates measured in equivalent length of pipe
in feet. When using the LATS Multi V software or when performing
manual calculations, the additional equivalent pipe length of all fit-
tings must be accounted for in the respective segments. See Table
23 on page 62.
Field-Provided Isolation Valves
LG neither provides nor requires isolation ball valves on indoor
units for proper system operation. If isolation is desired, full-port
isolation ball valves with Schrader ports (positioned between valve
and indoor unit) rated for use with R410A refrigerant should be
used on the liquid and vapor lines. Position the valves so they are
easily accessible for service. If necessary, install drywall access
doors or removable ceiling panels. Position valves with 3 to 6
inches of pipe on either side. Position valves with adequate clear-
ance for applying field insulation. If valves are not installed and
a single indoor unit needs to be removed or repaired, the entire
system must be shut down and evacuated. If isolation ball valves
are installed, the unaffected indoor units may be operated after
the control system is rebooted if the system CR (excluding the
disconnected unit) remains between 50% and 130%. See "How to
Determine the System Combination Ratio (CR)" on page 55.
Refrigerant Specialties
In-line refrigeration components, such as solenoid valves, filter-
dryers, sight glasses, tee fittings, and after-market refrigerant pipe
system accessories are prohibited and cannot be used with the
Multi V Mini. Sight-glasses, solenoid valves, and tee fittings may
cause gas bubbles to form in the liquid line. Over time, dryers
may deteriorate and introduce debris into the system.
Oil Traps
Oil traps are not permitted. The Multi V system is engineered with
redundant systems that ensure oil is properly returned to the com-
pressor. The designer and installer should verify that the refriger-
ant piping system is free of oil traps. For instructions on routing
a pipe segment around an obstacle, see "Handling Obstacles" on
page 74.
Summary of Contents for Multi V mini
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