CKT04 ADDENDUM
82
CTK04** COMFORTNET™ THERMOSTAT
Overview
The ComfortNet™ system (or CT system) is a system that
includes a ComfortNet compatible modular blower and air
conditioner with a CTK04** thermostat. The table below
compares the valid CT systems.
CT compatible Air Handler
or Modular Blower
CT compatible
Air Conditioner
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 thermostat.
On the other hand, the indoor unit, outdoor unit, and thermo-
stat comprising a ComfortNet system “communicate” digitally
with one another. It is now a two-way communications path.
The thermostat still sends commands to the indoor and out-
door 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 be-
tween the thermostat and subsystems (indoor/outdoor unit)
and between subsystems is the key to unlocking the benefits
and features of the ComfortNet system.
Two-way digital communications is accomplished using only
two wires. The thermostat and subsystem controls are pow-
ered with 24 VAC Thus, a maximum of 4 wires between the
equipment and thermostat is all that is required to operate
the system.
CTK04 WIRING
NOTE
: A removable plug connector is provided with the con-
trol 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 connect more
than two wires into a single terminal in the field because
there is a risk of the wires becoming loose.
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. Use
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).
System Wiring
System Wiring Using Four-Wires
Two wires only may be utilized between the indoor and out-
door units. For this wiring scheme, only the data lines, 1 and
2, are required between the indoor and outdoor units.