Equipment Selection Procedure - LG Multi V mini Engineering Manual

Always use LATS Multi V Software
To properly select and size Multi V system components, follow
these guidelines:
• Zone the building
• Determine the ventilation method
• Select the indoor unit(s)
• Select the outdoor unit
• System sizing checks
- Calculate the Corrected Capacity Ratio (CCR)
- Determine the system Combination Ratio (CR)
- Determine the Running (indoor) Unit Ratio (RUR)
The following procedure should not replace 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.
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 be adjusted to reflect the de-
signer's preferred indoor room design temperature. These indoor
room temperature values are the room thermostat setpoints and
should not be confused with entering coil conditions.
Data provided in the LATS tree mode diagram or
Note:
report file is not valid unless 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 re-run LATS.
Zone the Building
Multi V Mini Heat Pump is a two-pipe heat pump system that can
cool or heat, but not both simultaneously. Therefore, the designer
should combine spaces with similar load profiles located near or
adjacent to each other into "thermal zones." Calculate the peak
cooling and heating loads for each thermal zone.
Determine the Ventilation Method
Decide how ventilation air will be introduced to each space. Add
ventilation load(s) to the appropriate indoor unit(s) design cool-
ing and heating loads only if the ventilation air treatment system
does not provide room neutral air. Some models of Multi V indoor
units are factory provided with or have accessories available that
accommodate the direct connection of ventilation ductwork to
the unit. However, there are product limitations and additional
considerations that may need to be understood when using direct
connection accessories. For more information, contact your LG
applied equipment representative. Go to www.LG-VRF.com to find
your representative and technical product information.

EQUIPMENT SELECTION PROCEDURE

Due to our policy of continuous product innovation, some specifications may change without notification.
© LG Electronics U.S.A., Inc., Englewood Cliffs, NJ. All rights reserved. "LG" is a registered trademark of LG Corp.
In all cases, LG recommends ducting pretreated,
Note:
room neutral, ventilation air directly to the space. When
pretreated, ventilation air is provided, remember to de-
duct the ventilation airload(s) from the total load before
sizing the indoor unit(s). Local codes or other profession-
al 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 condi-
tions. This will minimize the possibility of ventilation air
conditions causing the indoor unit's entering air tem-
perature to fall outside the approved design temperature
range. For more information on how to properly size a
ventilation air pretreatment system, refer to the article,
"Selecting DOAS Equipment with Reserve Capacity" by
John Murphy, published in the ASHRAE Journal, April
2010.
Select the Indoor Unit(s)
Determine how many indoor units will be required. Refer to Table
1a to obtain the maximum number of indoor units allowed on a
system. If an indoor unit will serve more than one space (i.e.
ducted indoor unit or cassette equipped with up to two side branch
ducts), combine the space and ventilation loads for all rooms
served. If the quantity of indoor units exceeds the maximum
allowed for the outdoor model selected, consider increasing the
size of the outdoor unit or split the indoor units into two groups
served by separate outdoor units.
Calculate the entering mixed air conditions for each indoor unit.
The mixed-air temperature must be between 57°F and 76°F WB in
Cooling mode and between 59°F and 80°F DB in Heating mode.
When the indoor unit entering air temperature
Note:
is outside the cataloged operational limits, the system
may continue to operate properly; however, operational
abnormalities may occur. These include coil frosting, low
or high suction temperature, low or high head pressure,
low heating discharge temperature, or complete system
shutdown.
To calculate the indoor unit entering mixed air temperature:
(RAT x %RA) + (OAT x %OA)
MAT =
100
Where
MAT = Mixed air temperature
RAT = Return air temperature
OAT = Outdoor air temperature
%RA = Percentage of return air
%OA = Percentage of outdoor air
ARUN 036, 047, 053
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SYSTEM ENGINEERING
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