CACG/CAHG & CACH/CAHH
Air Handlers
• Installation, Operation and Maintenance Manual •
Comfort where it counts
54
P/N 240008108, Rev. B [082509]
Two-stage heating
Two-stage heating combines heat pump and
electric heat operation. Heat pump units
require an 18 AWG low-voltage intercon-
necting wire between the indoor unit and
the condenser. 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.
After connecting a two-stage heating ther-
mostat to the unit, place the system switch
in Heat mode.
Adjust the setpoint temperature above
1.
the room temperature so that first stage
heating is activated.
The compressor and fan motors will start
2.
and heating will begin.
Heating will continue as long as the set-
3.
point temperature remains above room
temperature.
To check for a low-voltage signal, place a
voltmeter across terminals :
“Y” and “C” of the outdoor unit.
•
“Y1” and “C” of the cassette.
•
When the unit is working correctly, there
should be a reading of 24 Vac.
Next, place the setpoint further above room
temperature to activate second stage heat-
ing.
Electric heat will energize (along with
1.
the compressor) when the deviation
between room temperature and setpoint
temperature is high enough to call for
second stage heating. (See the thermostat
owner’s manual for this feature).
Heating will continue as long as the
2.
setpoint temperature is above the room
temperature and the thermostat is calling
for second stage heating.
To check for an electric heat signal, place
3.
a voltmeter across terminals “W” and “C”
of the indoor unit.
When the unit is working correctly, there
4.
should be a reading of 24 Vac.
To stop heating operation, place the
5.
setpoint temperature below the room
temperature.
The outdoor unit and electric heat will
6.
stop while the indoor fan will remain on
for an additional sixty seconds.
Troubleshooting — CACG/CAHG Units
(continued)
