GSX14 Service Manual

SERVICING
69
Indoor Blower Motor
With power ON:
WARNING
Line Voltage now present.
1. Set fan selector switch at thermostat to "ON" position.
2. With voltmeter, check for 24 volts at wires C and G.
3. No voltage indicates the trouble is in the thermostat or
wiring.
4. Check the continuity of the thermostat and wiring. Repair
or replace as necessary.
Resistance Heaters
1. Set room thermostat to a higher setting than room
temperature so both stages call for heat.
2. With voltmeter, check for 24 volts at each heater relay.
Note: BBA/BBC heater relays are DC voltage.
3. No voltage indicates the trouble is in the thermostat or
wiring.
4. Check the continuity of the thermostat and wiring. Repair
or replace as necessary.
NOTE: Consideration must be given to how the heaters are
wired (O.D.T. and etc.). Also safety devices must be checked
for continuity.
S-3B COOLING ANTICIPATOR
The cooling anticipator is a small heater (resistor) in the
thermostat. During the "off" cycle, it heats the bimetal
element helping the thermostat call for the next cooling cycle.
This prevents the room temperature from rising too high
before the system is restarted. A properly sized anticipator
should maintain room temperature within 1 1/2 to 2 degree
range.
The anticipator is supplied in the thermostat and is not to be
replaced. If the anticipator should fail for any reason, the
thermostat must be changed.
S-3C HEATING ANTICIPATOR
The heating anticipator is a wire wound adjustable heater
which is energized during the "ON" cycle to help prevent
overheating of the conditioned space.
The anticipator is a part of the thermostat and if it should fail
for any reason, the thermostat must be replaced. See the
following tables for recommended heater anticipator setting
in accordance to the number of electric heaters installed.
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 or heat pump with a CTK0* thermostat. Any other
system configurations are considered invalid ComfortNet
systems and must be connected as a traditional (or legacy)
system. The table below compares the valid CT systems.
CT compatible Air Handler or
Modular Blower
CT compatible
Air Conditioner
Full CT system
benefits & features
CT compatible Air Handler or
Modular Blower
CT compatible
Heat Pump
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” digi-
tally 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 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 subsystems
(indoor/outdoor unit) and between subsystems is the key to
unlocking the benefits and features of the ComfortNet sys-
tem.
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.
CTK0* 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 improved by using a high quality, shielded, twisted
pair cable for the data transmission lines. In either case, 100
feet is the maximum length of wire between indoor unit and
outdoor unit, or between indoor unit and thermostat.
FOUR-WIRE INDOOR AND OUTDOOR WIRING
Typical wiring will consist of four wires between the indoor
unit and outdoor unit and between the indoor unit and
thermostat. The required wires are: (a) data lines, 1 and 2;
(b) thermostat “R” (24 VAC hot) and “C” (24 VAC common).