48
D
IAGNOSTICS
Accessing the furnace’s diagnostics menu provides ready ac-
cess to the last ten faults detected by the furnace. Faults
are stored most recent to least recent. Any consecutively
repeated fault is stored a maximum of three times. Ex-
ample: A clogged return air filter causes the furnace limit to
trip repeatedly. The control will only store this fault the
first three
consecutive
times the fault occurs.
NOTE:
It is highly recommended that the fault history be
cleared when performing maintenance or servicing the fur-
nace.
N
ETWORK
TROUBLESHOOTING
The indoor control is equipped with a bank of three DIP
switches that provide biasing and termination functions for
the communications transmission lines. The outdoor con-
trol in the communicating compatible unit is equipped with
a bank of two DIP switches that provide termination func-
tions for the communications transmission lines. Commu-
nications errors will result if these switches are not cor-
rectly set. Note that the ON position is the correct position
for furnace control board bias and pull up/pull down DIP
switches. Communications is achieved by the difference
between two DC signals. The signals and transmission
1
2
R C
1
2
R
C
CTK0*
Thermostat
ComfortNet Compatible
Furnace Integrated
Control Module
ComfortNet Compatible
AC/HP Integrated
Control Module
40VA Transformer
(included in CTK01 kit)
208/230 VAC
24 VAC
1
2
R C
System Wiring using Two-Wires between Furnace and AC/HP and
Four-Wires between Furnace and Thermostat
1
2
R C
C
Y
ComfortNet Compatible
Furnace Integrated
Control Module
CTK0*
Thermostat
Non-
Compatible
Single Stage AC
ComfortNet
G
W1 W2
Y1
Y2
O
1
2
R
C
4-Position Connectors
from CTK0*
Thermostat Kit
System Wiring between Furnace and Non-Communicating
Compatible Single Stage Air Conditioner
CTKO* 1 & 2
Thermostat
ComfortNet Compatible Furnace
Integrated Control Module
ComfortNet Compatible AC/HP
Integrated Control Module
System Wiring using Four-Wires
1
2
R
C
1
2
R
C
1
2
R
C
lines are referred to as “data 1” and “data 2.” Typically,
the data 1 line is approximately 2.8 VDC and the data 2
transmission line is approximately 2.2 VDC. The voltage
difference between data 1 and data 2 must be 0.6 VDC.
The ComfortNet™ system is a fully communicating system, and
thus, constitutes a network. Occasionally the need to trouble-
shoot the network may arise. The furnace control board has
some on-board tools that may be used to troubleshoot the net-
work. These tools are: red communications LED, green receive
(Rx) LED, and learn button.
•
Red communications LED – Indicates the status of
the network. The following table indicates the LED
status and the corresponding potential problem.
•
Green receive LED – Indicates network traffic. The
table below indicates the LED status and the
corresponding potential problem.
•
Learn button – Used to reset the network. Depress
the button for approximately 2 seconds to reset the
network.
