27
11.7 Conventional 24VAC Thermostat Control Wiring
The (-)ARL series of heat pumps allow the installer to use conventional 24VAC con-
trol wiring and a conventional thermostat for proper unit operation.
IMPORTANT: The preferred method of unit installation and operation is with the
Comfort Control
2
System™. The Comfort Control
2
System™ allows access to the
f
ault history of the system. This diagnostic information is not available when the
(-)ARL unit is using a conventional thermostat. Reference section 11.2 Comfort
Control
2
System™ Control Wiring.
Thermostat control wiring requires a minimum of four (4) wires for proper unit oper-
ation:
R – 24VAC
C – 24VAC common
Y1 – First stage operation
Y2 – Second stage operation
Optional wiring:
L – ICC fault information
L Terminal Output
• Flash 1 – Compressor running extremely long run cycle or low pressure
• Flash 2 – High pressure control trip
• Flash 3 – Unit short cycling
• Flash 4 – Locked rotor
• Flash 5 – Compressor will not run, open circuit
• Flash 6 – Open start circuit
• Flash 7 – Open run circuit
• Flash 8 – Control mis-operation
• Flash 9 – Low control voltage
When the L terminal from the outdoor unit is connected to a conventional thermo-
stat that is L terminal compatible, the thermostat display will flash the above codes.
If the low voltage control wiring is run in conduit with the power supply, Class I insu-
lation is required. Class II insulation is required if run separate. Low voltage wiring
may be run through the insulated bushing provided in the 7/8 hole in the base
panel, up to and attached to the pigtails from the bottom of the control box. Conduit
can be run to the base panel if desired by removing the insulated bushing.
A thermostat and a 24-volt, 40VA minimum transformer are required for the control
circuit of the condensing unit. The furnace or the air handler transformer may be
used if sufficient. See the wiring diagram for reference. Use Table 6 to size the 24-
volt control wirings.
CONVENTIONAL THERMOSTAT WIRING
SOLID COPPER WIRE - AWG.
3.0 16 14 12 10 10 10
2.5 16 14 12 12 10 10
2.0 18 16 14 12 12 10
50 100 150 200 250 300
Length of Run - Feet (1)
Thermostat Load - Amps
(1) Wire length equals twice the run distance.
NOTE: Do not use control wiring smaller than No. 18 AWG between thermostat and outdoor unit.
TABLE 6
FIELD WIRE SIZE FOR 24 VOLT THERMOSTAT CIRCUITS
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