Design Technical Manual

2-4. SELECTION OF PIPE HEAT INSULATING MATERIAL
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Always insulate the refrigerant pipe to prevent the formation of condensation and water
droplets.
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Decide the thickness of the heat insulating material by referring to the recommended
minimum thickness in Table 1. (For installation condition T=90°F DB (32°C DB),
humidity≤70%, humidity≤75%, humidity≤80%, humidity≤85%)
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When the outdoor unit is installed above the indoor units, be sure to ll the building
penetration with foam to prevent condensation in the outdoor unit from running down the
refrigerant pipes into the building.
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Both of the refrigerant lines (liquid and gas) should be insulated according to the same
specication.
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Water may leak from the refrigerant lines if the insulation is not completely sealed.
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Table1 Size of refrigerant pipe and recommended minimum thickness of heat insulating
material.
This is based on the insulating material having a thermal connectivity of .0040 W/(m*k).
Recommended minimum thickness for heat
insulating material [in. (mm)]
Relative humidity ≤70% ≤75% ≤80% ≤85%
Refrigerant
pipe
Outside
diameter
[in. (mm)]
1/4" (6.35) 5/16" (8) 13/32" (10) 1/2" (13) 21/32" (17)
3/8" (9.52) 11/32" (9) 7/16 " (11) 9/16" (14) 23/32" (18)
1/2" (12.70) 13/32" (10) 15/32" (12) 19/32" (15) 3/4" (19)
5/8" (15.88) 13/32" (10) 15/32" (12) 5/8" (16) 25/32" (20)
3/4" (19.05) 13/32 (10) 1/2" (13) 5/8 (16) 13/16" (21)
7/8" (22.22) 7/16 " (11) 1/2" (13) 21/32" (17) 7/8" (22)
1-1/8" (28.58) 7/16 " (11) 9/16" (14) 23/32" (18) 29/32" (23)
1-3/8" (34.92) 7/16 " (11) 9/16" (14) 23/32" (18) 15/16" (24)
1- 5/8" (41.27) 15/32" (12) 19/32" (15) 3/4" (19) 31/32" (25)
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In application where the ambient temperature and humidity exceed 90F DB (32C DB) and
95% relative humidity, increase the size of the pipe insulation. It may also be necessary to
insulate the indoor unit casing. Condensation may form on the insulation in these conditions
if the thickness of the insulation is not increased.
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Since the gas line gets very hot during heating operation, select a pipe insulation material
rated for at least 248F (120C).
Gas pipe (Low pressure) Gas pipe (Low pressure)
Gas pipe (High pressure)
Gas pipe (High pressure)
Connection cable
Finishing tape
Heat insulation
Heat insulation
Liquid pipe
Liquid pipe
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Make sure that the pipe is completely covered with insulation. Any exposed pipe could
cause condensation.
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Do not insulate both liquid and gas pipes together as shown in the gure above. This may
cause condensation and a drop in system capacity.
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SYSTEM DESIGN SYSTEM DESIGN