Lennox VRF VMDB Series Installation Instruction page 17

Outdoor unit
(main unit)
(PQ)
P Q
Install a terminating resistor (Ω120) at the last indoor unit terminals P and Q of the daisy chain.
All shields of shielded cable connect to
18 GA., stranded, 2-conductor, shielded control wire (polarity sensitive).
Typical Wiring Diagram, NEC/CEC and Local Codes apply.
Figure 23. Typical Communication Wiring Diagram (VRF Heat Pump System)
Tightening torque for the terminal screws
• Use the correct screwdriver for fighting the terminal
screws. If the screwdriver blade is too small, the head
of the screw might be damaged, and the screw will
not be properly tightened.
• If the terminal screws are over tightened, screws
might be damaged.
• Refer to the table below for the tightening torque of
the terminal screws.
• After wiring, confirm all connections are correct; Then
turn on power supply to the unit.
Outdoor unit Outdoor unit
(sub1 unit)
(H1 H2 ) (H1 H2 )
K1
(PQ)
chassis GROUND terminal at Indoor Units.
(sub2 unit)
(H1 H2 )
K2 O A
Outdoor Unit Communication Terminal Block
Table 3. Terminal Screw Tightening Torque
Terminal base of
remote controller/Signal
transmission wire (X2M)
Terminal base of power
supply (X1M)
Grounding terminal (M4)
DO NOT adjust DIP switch settings. Settings may only
be adjusted by a trained technician as part of the com-
missioning procedures.
17
X Y P Q
HA HB 12V COM P
Indoor Unit Communication Terminal Block
Ground cable shield
to Indoor Unit chassis
Tightening torque
0.58-0.72
0.87-1.06
1.06-1.43
IMPORTANT
H1 H2
Q
(lb-ft)