SERVICING
16
S-3E CTK0*** COMFORTNET
TM
THERMOSTAT
OVERVIEW
The ComfortNet™ system (or CT system) is a system that includes
a ComfortNet compatible modular blower and air conditioner
with a CTK0* 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 thermostat
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 outdoor
units. However, the thermostat may also request and receive
information from both the indoor and outdoor units. This infor-
mation 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 ther-
mostat and subsystems (indoor/outdoor unit) and between sub-
systems 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 powered
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
control to make thermostat wire connections. This plug may be
removed, wire connections made to the plug, and replaced. It is
strongly recommended that multiple wires into a single terminal
be twisted together prior to inserting into the plug connector.
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 im-
proved by using a high quality, shielded, twisted pair cable for
the data transmission lines. In either case, 250 feet is the maxi-
mum length of wire between indoor unit and outdoor unit, or
between indoor unit and thermostat.
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).
12RC
12RC
CTK04
Thermostat
Compatible
ir Handler/Furnace
Integrated Control Module
Compatible AC
Integrated Control Module
12RC
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.
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