Power Interruption Protection; Oil Return Mode 20 Seer Heat Pump Models; Ambient Temperature Sensor And Oil Return Mode - Trane ACONT900AC43UA Service Manual

Control Boards
Figure 10

Power Interruption Protection

If a short power interruption is detected, (0.1-1 sec-
ond) the control board will protect the compressor from
sudden restarts by initiating a power up delay of 70
seconds. If a power interrupt over 2 seconds is de-
tected, a 5 minute off time is started. During the time
delays, a Wait icon is displayed on the Comfort Con-
trol. The outdoor fan will be off during delay periods.

Oil Return Mode 20 Seer Heat Pump Models

This mode is activated during long low-stage opera-
tion to ensure proper oil return to the compressors in
heating mode low ambient conditions. When the sys-
tem is in Oil Return Mode the STATUS LED (see Fig-
ure 11) will flash at a medium speed (~2 times per
second)
Figure 11
The need for an Oil Return Mode will initiate a forced
Defrost Cycle. Defrost cycles terminate on time or tem-
perature.
The Oil Return Mode may be initiated below 28F after
3 hours of cumulative low stage compressor opera-
tion. Any Defrost Cycle will reset the Oil Return Mode
timer. Any high stage compressor operation (for at least
15 uninterrupted minutes) will reset the low stage run
timer at any outdoor air temperature.
HP - B 6
The Oil Return Mode may also be initiated below 45' F
after 8 hours of cumulative low stage compressor op-
eration. Any Defrost cycle will reset the Oil Return
Mode timer. Any high stage compressor operation (for
at least 5 uninterrupted minutes) will reset the low stage
run timer at any outdoor air temperature.
If ODT rises above the low temperature limit (28' F) the
low stage run timer will stop but if the outdoor air tem-
perature falls below the low temperature limit the low
stage run timer will resume.
There are two separate timers that can run concur-
rently, one for low temperature (below 28F) and one for
high temperature (between 28F and 45F thresholds.
This will ensure an Oil Return Mode execution if nec-
essary when outdoor air temperature crosses Low and
High temperature thresholds.
Ambient Temperature Sensor and
Oil Return Mode
The Integrated Control Board will use the Ambient Tem-
perature Sensor (see Figure 12) to monitor outdoor air
temperature. If there is a problem with the Ambient
Temperature Sensor, the following will occur:
Figure 12