Carrier 25HPA Performance Series Installation Instructions Manual page 14

QUIET SHIFT
This feature must be enabled by selecting the 3rd position of the
3- -position dip switch for a non- -communicating system or
enabling it at the User Interface in an Infinity communicating
system. Quiet Shift is a field selectable defrost mode that, when
activated, will eliminate occasional compressor sound that could
be heard at the start of defrost cycle and restart of heating cycle.
When the Quiet Shift is activated, and a defrost is initiated, the
following sequence of operation will occur. Reversing valve will
energize, compressor will turn off for 30 seconds, and then turn
back on to complete defrost. At the start of heating after
conclusion of defrost, reversing valve will de- - energize,
compressor will turn off for another 30 seconds, and the fan will
turn off for 40 seconds, before starting in the heating mode.
LIQUID LINE SOLENOID ACCESSORY
In heat pump long line applications, a liquid line solenoid is
required to control refrigerant migration in the heating mode. The
solenoid should be installed near the outdoor unit with the arrow
facing the outdoor unit. This is the direction of flow control. See
Long Line Application Guideline for details.
Accessory Liquid Solenoid with Infinity Communicating
Control: When using the Infinity Control, a liquid line solenoid
output labeled LS is provided. Connect the solenoid as shown in
the wiring label diagram. This is a 24vac output that is energized
w h en ev er th e co m p resso r i s en erg ized . It clo ses i n t h e
compressor- -off mode to prevent refrigerant migration into the
unit through the liquid line.
Accessory Liquid Solenoid with Non - - Communicating
Thermostat: The liquid solenoid is connected to the Y and C
terminal connections. The liquid solenoid closes in the
compressor- -off mode to prevent refrigerant migration into the
unit through the liquid line.
MAJOR COMPONENTS
Control Board
The Heat Pump control board controls the following functions:
S Compressor contactor operation
S Outdoor fan motor operation
S Reversing valve operation
S Defrost operation
S Compressor external protection
S Pressure switch monitoring
S Time delays
Field Connections
The control receives 24vac low- -voltage control system inputs
through the R, C, Y and O thermostat connections located at the
bottom of the control board (see Fig. 14) or the ABCD Infinity
connector at the bottom of the control board. The 24vac control
output terminal connection W2 is used during defrost. On
Infinity only, the 24vac LS (liquid solenoid) output terminal is
energized for the liquid solenoid accessory. The connection is
located at the bottom of the control board.
Compressor Internal Relief
The compressor is protected by an internal pressure relief (IPR)
which relieves discharge gas into the compressor shell when
differential between suction and discharge pressure exceeds
550- -625 psi. The compressor is also protected by an internal
overload attached to motor windings.
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