Mitsubishi Electric BDT CITY MULTI Installation And Pre-Commissioning Booklet page 9

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4. Outdoor Installation
4-3-6. Twinning on the outdoor unit side
• The pipe from multiple outdoor units must be installed so that oil will not accumulate in the pipe under certain
conditions. Refer to the figures below for details.
* Small dots in the figures indicate branching points.
In an R2 system: To a BC controller
A
(1) The pipe from the outdoor units must be inclined downward to the indoor unit side. In the figure on the right,
because the pipe is inclined upward, the oil in the pipe accumulates when Unit 1 is in operation and Unit 2 is
stopped.
Unit 1
A
(2) The distance between the unit bottom and the pipe (H) must be 0.2 m (7-7/8 in) or below. In the figure on the
right, because the distance is more than 0.2 m (7-7/8 in), the oil accumulates in Unit 1 when Unit 2 is in
operation and Unit 1 is stopped.
Unit 1
A
Unit 1
A
H
H ≤ 0.2 m (7-7/8 in)
(3) The vertical separation between units (H) must be 0.1 m (3-15/16 in) or below. In the figure on the right,
because the distance is more than 0.1 m (3-15/16 in), the oil accumulates in Unit 1 when Unit 2 is in operation
and Unit 1 is stopped.
Unit 1 Unit 1
A
(4) The vertical separation between units (H) must be 0.1 m (3-15/16 in) or below. In the figure on the right,
because the distance is more than 0.1 m (3-15/16 in), the oil accumulates in Unit 2 when Unit 1 is in operation
and Unit 2 is stopped.
Unit 1 Unit 1
H
A
• Make sure that the inclination tolerance of the Twinning Kit is ±15˚ to the ground to avoid unit damage.
• Do not install traps to prevent oil backflow and compressor start-up failure.
Unit 2
Unit 2
Unit 2
Unit 2
H
H ≤ 0.1 m (3-15/16 in)
Unit 2
H ≤ 0.1 m (3-15/16 in)
A
Unit 1 Unit 2
A
Unit 1 Unit 2
A
H
H > 0.2 m (7-7/8 in)
Unit 2
Unit 1
A
H
H > 0.1 m (3-15/16 in)
Unit 1
Unit 2
A
H
H > 0.1 m (3-15/16 in)
Twinning Kit
A
AN1 2nd
9