Multi F Engineering Manual

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Table Of Contents

Device Connection Limitations

• The minimum number of connected and operating indoor units to Multi F / Multi F MAX systems is two, taking into consideration the

minimum combination ratio.

• The maximum number of indoor units for each Multi F / Multi F MAX heat pump systems is:

LMU183HV = 2 LMU243HV = 3 LMU303HV = 4 LMU363HV = 4 LMU481HV = 8 LMU541HV = 8 LMU601HV = 8

PIPING LIMITATIONS

One of the most critical elements of multi-zone systems is the refrigerant piping. The following pages list pipe length limits that must be

followed in the design of Multi F and Multi F MAX refrigerant pipe systems:

Table 35: Equivalent Piping Length for Elbows, Y-branches, and Branch

Distribution Units.

Max. 49.2 feet

Max. 24.6 feet

Example of a Multi F System

Example: LMU363HV outdoor unit with four (4)

indoor units connected.

ODU: Outdoor Unit.

IDU: Indoor Unit.

A, B, C, D: Pipes from Outdoor Unit to Indoor Unit.

Outdoor Unit

Minimum Length for Each Pipe

(ft.)

Maximum Piping Length to Each Indoor Unit (ft.)

Maximum Total Piping Length for Each

System (ft.)

ABCD

LMU183HV 9.8 82 82 - - 164.0

LMU243HV 9.8 82 82 - - 230.0

LMU303HV 9.8 82 82 82 82 246.1

LMU363HV 9.8 82 82 82 82 246.1

Kit contains two Y-branches: one for liquid and one for vapor.

Table 36: Multi F Outdoor Unit Refrigerant Piping System Limitations.

Component

Size (Inches)

1/4 3/8 1/2 5/8 3/4

Elbow (ft.)

0.5 0.6 0.7 0.8 1.2

Y-Branch Kit (ft., Multi F MAX systems

only)

1.6

Branch Distribution Unit (ft., Multi F

MAX systems only)

8.2

Field-supplied elbows are allowed as long as they are designed for

use with R410A refrigerant. The designer, however, must be cau-

tious with the quantity and size of fittings used, and must account for

the additional pressure losses in equivalent pipe length calculation

for each branch. The equivalent pipe length of each elbow must be

added to each pipe segment.

Using Refrigerant Components

For allocated capacity information, see the combination tables in the “Multi F / Multi F MAX Combination Data Manual” on www.lghvac.com. For

performance data, see “Multi F / Multi F MAX Performance Data Manual” on www.lghvac.com.

Following pages present Multi F / MAX piping limitations and are for illustrative purposes only. Designers are highly encouraged to use LATS when

designing Multi F / MAX systems.

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PIPING AND PLACEMENT | 65

Piping Limitations and Placement Considerations

MULTI

MAX

MULTI