Daikin VRV REYQ96MTJU Design, Installation & Testing Instruction page 131

Si39-406
7.10.3 Example 3:
Situation Indoor unit was fitted with a drain trap but a leak occurred during subsequent operation.
Source of The trap was not properly shaped thus preventing it from functioning effectively as a trap and
resulting in drain leakage. The trap was reshaped and the fault disappeared.
Problem and
Remedial Action
Main Points
Reason: There is resistance on the air inlet side caused by the heat exchanger and air filter and this
in turn creates negative pressure in relation to the atmospheric pressure on the discharge side. If
there is no drain trap then air will be drawn in from the drain pipe and the waste water splashed
around giving rise to the risk of water overflowing from the drain pan. To avoid this problem it is
therefore necessary to design a trap which takes account of the maximum negative pressure which
is likely to be created on the suction side.
General Information
Drain pipe trap shape defective
Duct types (18~48) require a drain trap.
Appendix
125