Select The Indoor Unit(S); Heating Season; Cooling Season; Capacity Correction - LG Multi IV Engineering Manual

EQUIPMENT SELECTION PROCEDURE
data, see the separate Multi V IV Performance Data Manual on
www.lg-vrf.com.)
In lieu of designing for extreme weather conditions beyond the
cataloged temperature range, consider limiting the maximum
and / or minimum temperature of the air around the Multi V outdoor
air-cooled unit, or consider a Multi V water-cooled unit.
When installing a Multi V outdoor unit indoors, provide a conden-
sate drain pan with drain in locations where frozen run-off water
may present a slipping danger. Also, the air guide accessory (sold
separately) should be installed when mounting outdoor units indoors,
to prevent short cycling of discharge air.

Heating Season

Provide a ventilated equipment enclosure equipped with an auxiliary
heat source, or place the outdoor unit(s) within the confines of the
building envelope. On retrofit projects, it is best practice to
position the outdoor unit(s) in former chiller, boiler, or air handler
rooms. These strategies are commonly used on air-cooled projects
to eliminate "extreme" over-sizing of the outdoor unit(s).
The enclosure will eliminate other potential operational problems
from occurring, including the build-up of snow and ice on the unit
case, fan shroud and fan blade, limit the capacity reduction effect of
operating the outdoor unit at extremely low temperatures, and may
reduce the size and initial cost of the Multi V IV outdoor unit.

Cooling Season

An enclosure housing the outdoor unit or roof structure designed
to shade the outdoor unit will protect the unit(s) from the negative
impact of direct sun exposure, hail, and on sunny days, increase the
cooling capacity by reducing the refrigerant condensing temperature.
When the designer provides the LATS software with
ambient air design conditions that are above or below the cataloged
operational temperature range, the software will override the
system using the maximum or minimum cataloged ambient air
operating temperature. The report generated by LATS will re-
but the indoor and outdoor unit(s) cooling and heating corrected
capacities calculated and shown in the report will be based on
the cataloged ambient air operating temperature limits. On these
projects, the designer must manually estimate the corrected
ambient conditions are outside the cataloged range.

Select the Indoor Unit(s)

The building sensible cooling load is typically the critical load to
satisfy. In coastal areas or humid applications, such as high
occupancy spaces, both the latent and sensible cooling loads
should be considered. In areas where the cooling and heating loads
are similar or the heating load may exceed the total cooling load,
the designer should verify the indoor unit selection satisfies both the
heating and cooling requirements.
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Determine how many indoor units will be required. Refer to the
specification tables to obtain the maximum number of indoor units
allowed on Multi V IV Heat Pump and Heat Recovery units. If the
quantity of indoor units exceeds the maximum allowed for the out-
door 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. Verify the entering air
heating mode.
To calculate the indoor unit entering mixed air temperature:
Where:
MAT = Mixed air temperature
RAT = Return air temperature
Indoor unit nominal cooling capacity ratings, among other
parameters, are based on an entering air condition of 80°F DB /
67°F WB and a 95°F DB outdoor ambient temperature. Nominal
heating capacity ratings are based on an indoor unit entering air
condition of 70°F DB and an outdoor ambient air temperature of
47°F DB / 43°F WB.

Capacity Correction

The corrected cooling/heating capacity is different from the nominal
cooling / heating capacity. The corrected capacity reported by LATS
includes changes in unit performance after considering refrigerant
line pressure drop, the system's Combination Ratio (CR), and the
effect design ambient operating conditions has on the system's
cooling capability.
Depending on the location of the building, additional capacity
correction factors may need to be applied to the corrected capacity
values provided by LATS . (For correction factors, see the separate
Multi V IV Performance Data Manual on www.lg-vrf.com.)
Altitude Correction
On air-cooled systems, the impact of air density must be considered
on systems installed at a significant altitude above sea level. To
calculate the effect on the indoor unit's cooling capacity, manually
apply locally accepted altitude correction factors. LATS does not
de-rate indoor unit capacity for altitude.
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(RAT x %RA) + (OAT x %OA)
MAT =
100
When the indoor unit entering air temperature is outside the
cataloged operational limits, operational abnormalities may occur.
These include frost accumulating on the coil, low or high suction
temperature, low or high head pressure, low or high discharge
temperature, or complete system shutdown.
OAT = Outside air temperature
%RA = Percentage of return air
%OA = Percentage of outdoor air