Sequence Of Operation - American Standard 4TCA4024C1000A Installer's Manual

Sequence of Operation

G G e e n n e e r r a a l l
Operation of the system cooling (and optional heating)
cycles is controlled by the comfort control. Once the
comfort control is set to either H H E E A A T T or C C O O O O L L , unit
operation is automatic. The optional automatic
changeover control, when set to A A U U T T O O , automatically
changes to heat or cool with sufficient room
temperature change.
The fan can be set to O O N N , causing continuous
evaporator (indoor) fan operation or set to A A U U T T O O
causing fan operation to coincide with heating or
cooling run cycles. Continuous fan mode during
cooling operation may not be appropriate in humid
climates. If the indoor air exceeds 60% relative
humidity or simply feels uncomfortably humid, it is
recommended that the fan only be used in the A A U U T T O O
mode.
C C o o o o l l i i n n g g M M o o d d e e
With the comfort control set to C C O O O O L L and the fan set to
A A U U T T O O , the compressor contactor (CC) and the indoor
fan motor (IDM) are energized.
The energized compressor contactor (CC) completes
the circuit to the compressor (CPR) and a secondary
circuit to the outdoor fan motor (ODM). If the
compressor safety controls are closed, the compressor
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(CPR) will operate with the outdoor fan motor (ODM).
The indoor fan motor (IDM) will operate. The comfort
control will continue to cycle the compressor and fans
to maintain the desired temperature.
With the fan set to O O N N , the indoor fan motor (IDM) will
continue to run regardless of compressor and
condenser fan operation.
H H e e a a t t i i n n g g M M o o d d e e
Heating mode uses electric heaters, which are installed
separately. Refer to the Supplemental Electric Heaters
Installer's Guide for additional information.
On a call for heat, power from the comfort control is
received at "W1", which energizes the "AH" contactor
coil. The "AH" contactor closes powering the heater,
provided all element limits are closed. If two stages of
heat are provided and additional heat is required, the
comfort control's second stage "W2" circuit is
energized powering the "BH" contactor coil.
N N o o t t e e : : The indoor comfort control must be configured
to provide a "G" signal to energize the indoor
fan relay ( ( F F ) ) during the heating mode. The
heater control circuit will not be energized unless
the indoor fan relay ( ( F F ) ) is energized.
88-4TCA4002-1A-EN