CACG/CAHG & CACH/CAHH
Air Handlers
• Installation, Operation and Maintenance Manual •
Comfort where it counts
52
P/N 240007756, Rev. A [051509]
Troubleshooting — CACG/CAHG Units
Cooling-only units
Cooling only units require 18 AWG low-
voltage interconnecting wires between the
indoor and outdoor units. Also, interconnect
wiring is required between the indoor unit
and remote thermostat. Refer to low-voltage
interconnect diagram, Figure 42, Page 51, for
low-voltage connections.
NOTICE
Terminal “W” is required for units with
electric heat only.
Terminal “C” may not be needed on
some thermostats.
The wall mounted thermostat will switch the
outdoor unit on and off through the black ,“Y,”
and yellow, “Y1,” wires.
When the thermostat is calling for cooling,
24 Vac can be measured across terminals:
“Y” and “C” of the outdoor unit.
•
“Y1” and “C” of the cassette.
•
The cassette contains an electronic anti- short
-cycle timer feature (ASCT) that will prevent
the outdoor unit from short cycling. After the
thermostat is satisfied there will be a three
minute delay before the outdoor unit is al-
lowed to restart.
While the remote thermostat is calling for
cooling and the ASCT delay has elapsed,
24 Vac can be measured between terminals:
“Y” and “C” of the outdoor unit.
•
“Y1” and “C” of the cassette.
•
“G” and “C” of the cassette (fan signal).
•
Heat pump units
Heat pump units require 18 AWG low-voltage
interconnecting wire between the indoor and
outdoor units. Also, interconnect wiring is
required between the indoor unit and remote
thermostat. Refer to low-voltage interconnect
diagram, Figure 42, Page 51, for low-voltage
connections.
The wall mounted thermostat will switch the
outdoor unit on and off through the black ,“Y,”
and yellow, “Y1,” wires.
When the thermostat is calling for cooling or
heating, 24 Vac can be measured:
“Y” and “C” of the outdoor unit.
•
“Y1” and “C” of the cassette.
•
EMI heat pump systems utilize a revers-
ing valve is that is energized in the cooling
mode.
Heat pump units will operate the com-
1.
pressor in heating mode while the revers-
ing valve is de-energized.
The reversing valve signal is provided
2.
through the orange, “O,” low-voltage
wire of the thermostat. It should remain
energized constantly as long as the ther-
mostat’s system switch remains in Cooling
mode.
To check for 24 Vac reversing valve volt-
3.
age at the outdoor unit, place a voltmeter
across the brown, “C,” and orange, “O,”
wires while in the Cooling mode. The
meter should read 24 Vac.
NOTICE
Terminal “O” is required for heat pump
operation. The reversing valve is ener-
gized in cooling.
Terminal “W” is required for units with
electric heat only.
Terminal “C” may not be needed on
some thermostats.
