3
Lennox
Communicating
Outdoor Unit
Lennox
Communicating
Thermostat
Indoor Unit Communicating Control
(Using 2-conductor Unshielded Cable for Communication Lines and
Separate 2-conductor Unshielded Cable for R and C)
OPTION 3
18/2 Brown Solid CU CL2 Thermostat Wire
Figure 2. Lennox Communicating System Wiring Connections using
Separate Unshielded Cable (Option 3)
1.2. Minimizing Electrical Noise
When using multi-conductor unshielded thermostat cable, to minimize electrical
noise, cap unused wires as illustrated below and run to indoor unit C terminal.
Single wire
to indoor unit
terminal “C”.
Unused
wires
Single wire directly to
C terminal or
to second bundle.
.
Indoor Unit Controller
Outdoor Unit
Thermostat
R i+ I- C
Unused
wires
Figure 3. Minimizing Electrical Noise
2. Soft Disable
Soft disabling is when the Lennox communicating thermostat finds an unknown
control on the S30/S40 system communication bus. The thermostat sends the
unknown control a message to go into soft disable mode until the component is
properly configured or removed.
Sometimes soft disable will occur when a control is being replace. Reconfiguring
the system should resolve this issue.
Lennox communicating thermostats will not show a alert code for a soft disabled
control. When soft disabling occurs only the control that has been disabled will
display the blinking LED status or seven-segment display indicator. Refer to the
device’s installation and setup guide for further guidance.