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Si39-406 Refrigerant Piping Work
Installation Manual BS Unit 181
6. Refrigerant Piping Work
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This section describes how to connect the piping to the BS unit. Select the piping size based on
the procedure outlined here.
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Regarding piping work between the outdoor unit and the BS unit, selection of the branch kit, and
the piping work between the branch kit and the indoor unit, see the installation manual for the
outdoor unit and other technical documents.
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Always check that the refrigerant to be used is R410A before starting work. (If the wrong
refrigerant is used, the unit will not operate normally.)
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Completely insulate the discharge and suction piping both liquid and gas. Not insulating them
may cause leaking or burns. Only use insulating material which is resistant to 250°F or higher. If
you think the humidity in the ceiling might exceed 86°F and RH80%, reinforce the insulation on
the cooling piping (at least 13/16’’ thick). Condensation might form on the surface of the
insulation.
CAUTION
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Use a pipe cutter and flare suitable for R410A.
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Use a piping branch pipe kit selected based on the selection procedure for refrigerant branch
kits.
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See the installation manual for the outdoor unit and other relevant technical documents for
details on refrigerant branch kit selection, maximum piping length, maximum height difference,
and maximum length after branch.
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Apply ether oil or ester oil around the flare portions before connecting.
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Only use the flare nuts included with the unit. Using different flare nuts may cause the
refrigerant to leak.
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To prevent dust, moisture or other foreign matter from infiltrating the tube, either pinch the end
or cover it with tape.
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The outdoor unit is charged with refrigerant.
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Be sure to use both a spanner and torque wrench together when connecting or disconnecting
pipes to/from the unit.
(Refer to Fig. 2)
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When connecting the flare nut, coat the flare both inside and outside with refrigerating machine
oil and initially tighten by your hand 3 or 4 turns.
(Refer to Fig. 3)
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Refer to the Table 1 for the measurements of tightening torque and flare. Overtightening may
damage the flare.
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Refer to Table 2 if no torque wrench is available.
Using a wrench to tighten flare nuts causes the tightening torque to suddenly grow much tighter
after a certain point. From there, tighten the nut further by the appropriate angle listed in Table
2. After this is done, make sure no gas is leaking.
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When brazing the refrigerant piping, perform nitrogen replacement (note 1) first or perform the
brazing (note 3) while feeding nitrogen into the refrigerant piping (note 2), and finally connect
the indoor unit and BS unit using the flare or flange connections.
Notes
1. For details on nitrogen replacement, see the “VRV Installation Manual” (available at any Daikin
dealer).
2. When feeding nitrogen into the pipes while doing the brazing, the pressure-reducting valve
should be set to 2.9psi. (Refer to Fig. 5)
3. Do not use a flux when brazing the refrigerant pipe joints.
Use phosphor copper brazing (B cup) which does not require flux.
(Using a chlorine flux may cause the pipes to corrode, and if it contains fluoride it may cause the
refrigerant lubricant to deteriorate, adversely affecting the refrigerant piping system.)
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Piping connections should be checked for gas leaks and then, referring to Fig. 4, insulated using
the included joint insulating material 3) on all liquid and gas pipes (a total of 5 locations) (Tighten
both edges with clamp 2).) Use the included joint insulating material.