Lennox VRF VMDB Series Installation Instruction page 16

Outdoor unit Outdoor unit
(sub1 unit)
(main unit)
(H1 H2 )
(H1 H2
(PQ)
(PQ)
MS
Box
(PQ)
P Q
Install a terminating resistor (Ω120) on terminals P&Q on the indoor unit
which is furthest from the outdoor unit.
All Drain Wires will connect from outdoor unit chassis to mode selection box chassis at the end of
the signal run.
18 GA., stranded, 2-conductor, shielded control wire (polarity sensitive).
Typical Wiring Diagram, NEC/CEC and Local Codes apply.
NOTE - Each communication wire from the MS box should follow the refrigerant piping for that port.
Figure 22. Typical Communication Wiring Diagram (VRF Heat Recovery System)
Outdoor unit
(sub2 unit)
K1 K2
) (H1 H2 )
(PQ) (PQ)
(PQ)
O A X Y
Outdoor Unit Communication Terminal Block
MS
Box
Indoor Unit Communication Terminal Block
16
P Q H1 H2
P Q
MS Box Communication
Terminal Block
HA HB 12V COM P Q
Ground drain wire or
cable shield
to MS Box
and Outdoor Unit chassis