Selection Of Pipe Heat Insulating Material - Fujitsu AIRSTAGE J-IIIL Design & Technical Manual

2-4. Selection of pipe heat insulating material

Always insulate the refrigerant pipe to prevent condensation and water droplets by the refrigerant
pipe. For selection of pipe heat insulating material, refer to following items.
• Decide the thickness of the heat insulating material by referring to the recommended minimum
thickness in Table 1. (For installation condition T = 90 °FDB [32 °CDB]), humidity ≤ 70%, humidity
≤ 75%, humidity ≤ 80%, humidity ≤ 85%)
Table 1. Size of refrigerant pipe and recommended minimum thickness of heat insulating material
In case a heat insulating material which thermal conductivity is equal to or less than 0.040 W/(m•k)
is used.
Relative humidity
Refrigerant pipe
outside diameter
(in [mm])
• When the outdoor unit is installed in a higher position than the indoor unit, fill the connecting part
gap with putty, etc. to prevent the dew condensation water of the valve of the outdoor unit from
flowing to the indoors from the gap between the pipe and the heat insulating material.
• Liquid pipe and gas pipe should be completely insulated with same specification.
• Water may leak from the refrigerant lines if the insulation is not completely sealed.
• In application where the ambient temperature and humidity exceed 90 °FDB (32 °CDB) 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.
• Since the gas line gets very hot during heating operation, select a pipe insulating material rated for
at least 248 °F (120 °C).
• Make sure that pipe is covered completely by the heat insulation, not exposing to air. Inadequate
heat insulation may cause condensation.
• Do not cover heat insulation gas and liquid pipes together as figure below. It may cause conden-
sation and capacity drop by heat loss.
2-4. Selection of pipe heat insulating material
Recommended minimum thickness for heat insulating material
≤ 70%
1/4 (6.35) 5/16 (8)
3/8 (9.52) 11/32 (9)
1/2 (12.70) 13/32 (10)
5/8 (15.88) 13/32 (10)
3/4 (19.05) 13/32 (10)
7/8 (22.22) 7/16 (11)
1-1/8 (28.58) 7/16 (11)
Gas pipe
Connection cable
Finishing tape
Liquid pipe
Heat insulation
in (mm)
≤ 75%
13/32 (10)
7/16 (11)
15/32 (12)
15/32 (12)
1/2 (13)
1/2 (13)
9/16 (14)
Gas pipe
- (06-25) -
≤ 80% ≤ 85%
1/2 (13) 21/32 (17)
9/16 (14) 23/32 (18)
19/32 (15) 3/4 (19)
5/8 (16) 25/32 (20)
5/8 (16) 13/16 (21)
21/32 (17) 7/8 (22)
23/32 (18) 29/32 (23)
Liquid pipe
Heat insulation
2. Piping design