44
Low Voltage Controls
Optional Heat Pump
With Electric
Heat
Applications
Heat Pump systems utilize 6 low volt interconnecting wires
between indoor, and outdoor.
24v transformer located in indoor air handler provides low
volt control power to both air handler and condenser.
• Air handlers require contacts wired to same
name indoors and outdoors, COM1, COM2, SC,
24vDC(-), Rv and Rv. COM1 and COM2 carry serial
digital communications between indoor and outdoor
units.
• SC and 24vDC(-) carry Direct Current power, not
Alternating Current.
• Rv and Rv carry 24 volt alternating current to reversing
valve, which is non-polarized.
Heating
Interconnect Wiring
• Unit-mounted controls see Figure 30 and 31,
Page 22.
• Wired wall controller applications see Figure 34 and 35,
Page 22.
Checking Voltage
Voltage Check
is accomplished at either indoor or outdoor
unit.
• 24v transformer located in indoor air handler provides
low volt control power to both air handler and
condenser between SC and 24vDC(-) terminals.
• This is DC voltage use proper scale.
• Reversing valve is energized in Cooling mode and de-
energized in Heating mode. When 24 volts AC exists
between Rv and Rv (indoors or outdoors) system is in
cooling mode. In Cooling mode, 24 volt power exists
between the Rv and Rv terminals. When zero (0) volts
AC exists between Rv and Rv, system is in Heating
mode or there is open circuit to reversing valve in
Cooling mode.
TRoUBLESHooTInG - CAHV UnITS
Cooling-only Units
• Cooling only units require 18 AWG low-voltage
interconnecting wires between indoor and outdoor
units.
• Interconnect cored is required between indoor unit and
wired wall control.
• Refer to low-voltage interconnect diagram. See
Figure 30, Page 19.
Low Voltage Controls — Cooling-only Units
Cooling-only units utilize 4 low volt interconnecting wires
between indoor, and outdoor.
• Air handlers using unit-mounted controls require
contacts wired to same name indoor and outdoor,
COM1, COM2, SC, and 24vDC(-). COM1 and COM2
carry serial digital communications between indoor and
outdoor units.
• SC and 24vDC(-) carry Direct Current power, not
Alternating Current power.
Interconnect Wiring
• Unit-mounted controls see Figure 30 and 31, Page 19.
• Wired wall controller applications see Figure 34 and 35,
Page 22.
Cooling
Voltage Check
is accomplished at either indoor or outdoor
unit.
• 24v transformer located in indoor air handler provides
low volt control power to both air handler and
condenser between SC and 24vDC(-) terminals.
• This is DC voltage, use proper scale on meter.
• 24 vDC can be measured across terminals:
24vDC(-)
SC
electric Heat Applications
Units with electric heat utilize control relay located on air
handlers control board in control box.
• Auto-reset limit switch located on heater end plate or
on heater assembly interrupts power to heater should
overheat condition occur.
• Electric heat assembly is equipped with one-time fuse
link. Should electric heat temperatures rise above auto
resetting limit switch, non-resetting, one-time fusible
link opens and heater remains“OFF”.
• To restart, new fuse link is required. Do not replace
fusible link with simple wire conductor.
• Following current values apply when unit is connected
to 230v power supply. values include fan motor
current. If supply voltage is different, amperage
changes.
3kw = 13.5 Amps
1.5kw = 6.9 Amps
