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The following procedure is a representation on how LATS Multi
V Piping Design software works when designing a Multi V HVAC
system. It should not replace the use of LG's LATS Multi V
complimentary selection software, but should instead be used in
conjunction with it. Contact your LG representative to obtain a
copy of the software and the user's manual.
Always use LATS Multi V Software
To properly select, size, and verify that the Multi V system
components are optimized, follow the recommendations and
instructions provided in this section:
• Zone the building.
• Determine the ventilation method.
• Select the indoor unit(s).
• Select the outdoor unit(s).
• Perform system sizing checks.
• Calculate the Corrected Capacity Ratio (CCR).
• Determine the system Combination Ratio (CR).
• Determine the Running (indoor) Unit Ratio (RUR).
When using the LATS Multi V software, the default indoor design day
conditions of 80.6°F DB / 67°F WB in cooling mode and 68°F DB /
56.7°F WB in heating mode may need to be adjusted to reflect the
designer's preferred return air design temperature.
valid until the "Auto-Piping" and "System Check" routines are run
without errors. Errors will be reported immediately in pop-up
dialog boxes or red lines surrounding indoor unit(s) and / or along
pipe segments. If errors are indicated, modify the pipe system
design and / or system components and re-run LATS.
Zone the Building–Multi V IV Heat
Pump Systems
Multi V IV Heat Pump is a two-pipe heat pump system that can cool
or heat, but not both simultaneously. When designing a heat pump
system, the designer typically combines spaces with similar load
profiles located near or adjacent to each other into "thermal zones."
After combining like spaces into thermal zones that will be served by
a single (or grouped) indoor unit(s), calculate the peak cooling and
heating loads for each thermal zone.
Zone the Building–Multi V IV Heat
Recovery Systems
Multi V IV Heat Recovery is a three-pipe heat pump system that
can cool and heat simultaneously. To maximize the amount of heat
recovered and optimize the system operating efficiency, it is best
to combine spaces that require heating and cooling concurrently
on each Multi V pipe system. LG multi-port heat recovery units are
designed to serve spaces that need cooling and others that need
heating at the same time. The heating/cooling operating mode
selection is made at the heat recovery units' outbound pipe port,
independent of the adjacent ports' operating mode.
In many buildings, to optimize system design, spaces on opposite
sides of the building are combined on a single pipe system served by
a common Multi V IV Heat Recovery outdoor unit. If the building
has multiple floors, connected load diversity is often maximized by
combining spaces located on different floors (maximum 131 feet
vertical height difference between indoor system components). Each
building will be unique. To discover the best combination of spaces,
use a building energy modeling software.
Calculate the Ventilation Method
Decide how ventilation air will be introduced to each space. Some
models of Multi V indoor units have field-installed accessories
available to accommodate the direct connection of ventilation
ductwork to the unit. It is recommended, however, that additional
considerations be assessed and understood when using direct
connection accessories. For more information, contact your LG
applied equipment representative or visit for
technical product information.
In all cases, LG recommends ducting pre-treated room neutral,
ventilation air directly to the space. If the ventilation air is not
tempered to room neutral conditions before introduction to the
conditioned space, remember to add the ventilation air load(s) to
the space load before sizing the indoor unit(s). Local codes or
other professional design guidelines, such as ASHRAE 62.1, will
dictate the volume of ventilation air required.
It may be prudent to oversize the dedicated outdoor air system
considering there will be a few days of the year when weather
conditions exceed the design day conditions. This will minimize
the possibility of ventilation air conditions causing the space
temperature to drift outside design day parameters in the case where
a decoupled outside air system is used, or the indoor unit's entering
air temperature falls outside the approved design temperature range
if a coupled outside air system is used.
Designing for Extreme Climatic
The Multi V IV air-cooled outdoor unit(s) may have to operate in
weather conditions more extreme than a typical design day. Design
days are the days of the year that either cooling or heating capacity
is needed the most. In light of this, it may be prudent to size the
outdoor unit considering the anticipated worst weather day
conditions to ensure adequate capacity year round.
When design outdoor ambient conditions are outside the cataloged
air-cooled outdoor unit operating range, the net refrigeration effect
(capacity) delivered to the indoor units cannot be guaranteed. As a
result, the outdoor unit's net refrigeration capacity available for use
by the indoor units will be slightly reduced under certain extreme am-
bient air conditions. (For cooling and heating capacity performance
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