SERVICING
49
CTK04 ADDENDUM
CTK04 ADDENDUM
7-SEGMENT DISPLAY
CTK04** COMFORTNET™ THERMOSTAT
OVERVIEW
The ComfortNet™ system (or CT system) is a system that
includes a ComfortNet compatible modular blower heat
pump condenser with a CTK04** thermostat. The table
below compares the valid CT systems.
CT compatible Air Handler
or Modular Blower
CT compatible
Heat Pump Unit
Full CT system
benefits &
features
A ComfortNet heating/air conditioning system differs from a
legacy/traditional system in the manner in which the indoor
unit, outdoor unit and thermostat interact with one another.
In a traditional system, the thermostat sends commands
to the indoor and outdoor units via analog 24 VAC signals.
It is a one-way communication path in that the indoor and
outdoor units typically do not return information to the ther-
mostat.
On the other hand, the indoor unit, outdoor unit, and ther-
mostat comprising a ComfortNet system “communicate”
digitally with one another. It is now a two-way communica-
tions path. The thermostat still sends commands to the in-
door and outdoor units. However, the thermostat may also
request and receive information from both the indoor and
outdoor units. This information may be displayed on the
CT thermostat. The indoor and outdoor units also interact
with one another. The outdoor unit may send commands to
or request information from the indoor unit. This two-way
digital communications between the thermostat and subsys-
tems (indoor/outdoor unit) and between subsystems is the
key to unlocking the benefits and features of the Comfort
-
Net system.
Two-way digital communications is accomplished using
only two wires. The thermostat and subsystem controls are
powered with 24 VAC Thus, a maximum of 4 wires be-
tween the equipment and thermostat is all that is required to
operate the system.
CTK04 WIRING
NOTE: A removable plug connector is provided with the
control to make thermostat wire connections. This plug
may be removed, wire connections made to the plug, and
replaced. It is strongly recommended that you do not con-
nect more than two wires into a single terminal in the field
because there is a risk of the wires becoming loose. Failure
to do so may result in intermittent operation.
Typical 18 AWG thermostat wire may be used to wire the
system components. However, communications reliability
may be improved by using a high quality, shielded, twisted
pair cable for the data transmission lines. In either case,
250 feet is the maximum length of wire between indoor unit
and outdoor unit, or between indoor unit and thermostat.
Please use a thermostat model later than CTK04AE.
TWO-WIRE OUTDOOR, FOUR-WIRE INDOOR WIRING
Low voltage wiring consists of two wires between the indoor
unit and outdoor unit and four wires between the indoor unit
and the thermostat. The required wires are: (a) data lines,
1 and 2; (b) thermostat “R” (24 VAC hot) and “C” (24 VAC
common).
1
2
C
R
1
2
R
C
1
2
R
C
Communic
a�
ng Thermostat
( In case of
CTK04AE
)
125
�. (*)
Air Handler Blower
Gas Furnace or Module Blower
Integrated Control Module
250
�. (*)
Outdoor unit
Integrated Control Module
(
*
) Allowable Maximum Length
SYSTEM WIRING
SYSTEM WIRING USING FOUR-WIRES
Two wires only may be utilized between the indoor and
outdoor units. For this wiring scheme, only the data lines, 1
and 2, are required between the indoor and outdoor units.
