Defrost (50Tfq004-007); Defrost (50Tfq008-012); Apollo Communicating Control Wiring Schematic - Carrier 50TFQ004 Product Data

Defrost (50TFQ004-007) — As frost builds up on the
outdoor coil, the coil temperature drops below 28 F. When
this outdoor-coil temperature drop is sensed by the defrost
thermostat (DFT) and the defrost timer is at the end of a
timed period (adjustable at 30, 50, or 90 minutes), the unit
operates in a defrost cycle controlled by the defrost timer
and thermostat. During this cycle, the reversing valve sole-
noid (RVS) is energized and the outdoor fan shuts off. The
electric heaters (if installed) will be energized.
The unit continues to defrost until the coil temperature
as measured by DFT reaches 65 F, or the duration of de-
frost cycle completes a 10-minute period.
At the end of the defrost cycle, the electric heaters (if in-
stalled) and the reversing valve will be deenergized, and the
outdoor-fan motor will be energized. The unit will now op-
erate in the Heating mode.
If the thermostat is satisfied during a defrost cycle, the
unit will continue in the Defrost mode until the time or tem-
perature constraints are satisfied.
Defrost (50TFQ008-012) — When the temperature of
the outdoor coil drops below 28 F as sensed by the defrost
thermostat (DFT2) and the defrost timer is at the end of a
C — Contactor
CHAS — Ground
COM — Common
DX — Direct Expansion SAT — Saturated-Air Temperature
ECON — Economizer
GND — Ground
HT — Heat

APOLLO COMMUNICATING CONTROL WIRING SCHEMATIC,

50TFQ004-007 UNITS
LEGEND
NC — Normally Closed
NO — Normally Open
OAT — Outdoor-Air Thermostat
VVT — Variable Volume/Variable
Temperature
timed period (adjustable at 30, 50, or 90 minutes), revers-
ing valve solenoids (RVS1 and RVS2) are energized and
the OFC is deenergized. This switches the position of the
reversing valves and shuts off the outdoor fan. The electric
heaters (if installed) will be energized.
The unit continues to defrost until the coil temperature
as measured by DFT2 reaches 65 F, or the duration of de-
frost cycle completes a 10-minute period.
During the Defrost mode, if circuit 1 defrosts first, RVS1
will oscillate between Heating and Cooling modes until the
Defrost mode is complete.
At the end of the defrost cycle, the electric heaters (if in-
stalled) will be deenergized; the reversing valves switch and
the outdoor-fan motor will be energized. The unit will now
operate in the Heating mode.
If the space thermostat is satisfied during a defrost cycle,
the unit will continue in the Defrost mode until the time or
temperature constraints are satisfied.
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