SERVICING
19
S-1 CHECKING VOLTAGE
1. Remove outer case, control panel cover, etc., from unit
being tested.
With power ON:
WARNING
LINE VOLTAGE NOW PRESENT.
2. Using a voltmeter, measure the voltage across terminals
L1 and L2 of the contactor for the condensing unit or at
the field connections for the air handler or heaters.
ComfortNetTM Ready Condensing Units:
Measure
the voltage across the L1 and L2 lugs on the unitary
(UC) control.
3. No reading - indicates open wiring, open fuse(s) no
power or etc., from unit to fused disconnect service. Re-
pair as needed.
4. With ample voltage at line voltage connectors, energize
the unit.
voltage
min.
max.
Outdoor Unit, Air Handler,
Modular Blower, Heater Kit
208/230
197
253
Gas Furnaces
115
103
126
Unit Type
Unit Supply Voltage (VAC)
NOTE
: When operating electric heaters on voltages other
than 240 volt, refer to the System Operation section on elec-
tric heaters to calculate temperature rise and air flow. Low
voltage may cause insufficient heating.
S-2 CHECKING WIRING
WARNING
HIGH VOLTAGE
DISCONNECT ALL POWER BEFORE SERVICING
OR INSTALLING THIS UNIT. MULTIPLE POWER
SOURCES MAY BE PRESENT. FAILURE TO DO SO
MAY CAUSE PROPERTY DAMAGE, PERSONAL IN-
JURY OR DEATH.
1. Check wiring visually for signs of overheating, damaged
insulation and loose connections.
2. Use an ohmmeter to check continuity of any suspected
open wires.
3. If any wires must be replaced, replace with comparable
gauge and insulation thickness.
S-3 CHECKING THERMOSTAT AND WIRING
Communicating Thermostat Wiring: The maximum wire
length for 18 AWG thermostat wire is 250 feet.
S-3A THERMOSTAT AND WIRING
WARNING
LINE VOLTAGE NOW PRESENT.
With power ON, thermostat calling for cooling
1. Use a voltmeter to check for 24 volt at thermostat wires
C and R in the indoor unit control panel.
2. No voltage indicates trouble in the thermostat, wiring or
transformer source.
3. Check the continuity of the thermostat and wiring. Re-
pair or replace as necessary.
WARNING
LINE VOLTAGE NOW PRESENT.
Resistance Heaters
With power ON:
1. Set room thermostat to a higher setting than room tem-
perature so both stages call for heat.
2. With voltmeter, check for 24 volt at each heater relay.
3. No voltage indicates the trouble is in the thermostat or wiring.
4. Check the continuity of the thermostat and wiring. Re-
pair 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-3E DAIKIN COMMUNICATING THERMOSTAT
OVERVIEW
The communication system is a system that includes a com-
munication system compatible indoor unit and outdoor unit
with a communicating 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 communication heating/air conditioning system differs
from a non-communicating/traditional system in the manner
in which the indoor unit, outdoor unit and thermostat inter-
act 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 informa-
tion to the thermostat. On the other hand, the indoor unit,
outdoor unit, and thermostat comprising a communication
system communicate digitally with one another. It is now a
two-way communications path.
