Engineering Manual

EQUIPMENT SELECTION PROCEDURE
Table 90: Allowable Indoor Unit to Outdoor Unit Connections.
Choosing the Appropriate Outdoor Unit
After all indoor units are properly sized to offset the applicable loads in each zone, select the outdoor unit by choosing a size that meets
both the load-cooling requirement, and offsets the sum of the heating load. Then, the system’s combination ratio should be evaluated and
confirmed it is within the allowable range (the combination ratio compares the nominal capacity of all connected indoor units to the nominal
capacity of the outdoor unit serving them). The total nominal capacity of all indoor units should be smaller than the total nominal capacity of
the outdoor unit. If the combination ratio is more than 100%, the designer is undersizing the outdoor unit relative to the combined nominal ca-
pacity of the connected indoor units. In some designs, oversized indoor units may be unavoidable in the case where the smallest size indoor
unit available from LG is larger than what is necessary to satisfy the zone load. This scenario may also occur when an indoor unit selection
one size down from the selected unit is slightly short of fulfilling the design load requirements, and the designer must choose the next larg-
est size unit. Sometimes it is recommended to choose a larger capacity outdoor unit if the installation space is big enough. Also, it may be
prudent to oversize the outdoor unit to address those times when the weather conditions may exceed the design conditions, to minimize the
possibility of ventilation systems that causes the space temperature to drift outside design parameters, or when the indoor unit’s entering air
temperature falls outside the approved design temperature range.
Branch Distribution Unit (PMBD3620)
+
24 x 1.2 24 x 1.2 + Total Capacity Index = = 57.6 < 73
Branch Distribution Unit (PMBD3641)
First Indoor Unit:
LMCN125HV
+ + Outdoor Unit: LMU540HV
12 9 36 x 1.3 + + Total Capacity Index = = 67.8 < 73
Acceptable
Combination
Second Indoor Unit:
LSN090HSV4
Third Indoor Unit:
LMVN360HV
Outdoor Unit: LMU540HV
First Indoor Unit:
LMVN240HV
Second Indoor Unit:
LMVN240HV
Acceptable
Combination
Example 1
Example 2
Multiplier Examples
Indoor units Outdoor units
Model Type
Indoor Unit Nominal
Capacity (Btu/h)
LMU18CHV LMU24CHV LMU30CHV LMU36CHV LMU480HV LMU540HV LMU600HV
Maximum No. of Connectable Indoor Units
2344888
ART COOL Mirror
9,000 OOOOOOO
12,000 O O O O O O O
18,000 - O O O O O O
ART COOL Gallery
9,000 OOOOOOO
12,000 OOOOOOO
Standard Wall Mounted
7,000 OOOOOOO
9,000 OOOOOOO
12,000 O O O O O O O
15,000 O O O O O O O
18,000 - O O O O O O
24,000 - O O O O O O
Ceiling Concealed Duct-
Low Static
9,000 O O O O O O O
12,000 O O O O O O O
18,000 - O O O O O O
Ceiling Concealed Duct-
High Static
24,000 - - O O O O O
36,000 - - - - O O O
Four-Way Ceiling Cassette
7,000 OOOOOOO
9,000 OOOOOOO
12,000 OOOOOOO
18,000 - O O O O O O
Vertical-Horizontal Air Handler
24,000 - - O O O O O
36,000 - - - - O O O
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