Heatcraft H-IM-QRC, Installation And Operation Manual, Page: 18 / 40

18
Power Failures
In the event of a power failure, Heatcraft Quick Response Controller
will automatically close the expansion valve to prevent refrigerant
from migrating throughout the system. After power returns, with 24
VAC at the board, the system will restart in the cooling mode after
the four-minute hold off period.
Spare Sensor Terminals
Heatcraft Quick Response Controller provides a set of input terminals
for customers who may want to monitor an additional temperature
or items such as Product Temperature. This input terminal requires
a signal from a thermistor which meets the temperature/resistance
values in Table 1 on page 21.
If a product temperature simulator is used, it must meet the
resistance/temperature specification listed in Table 1. The
temperature range for this input is –30°F to 140°F. Sensors on the
Heatcraft Quick Response Controller system, as supplied, will not
simulate product temperature.
This input can be monitored on the LED display by using the
“
MONITOR ” button and scrolling to
SPt
. The values displayed will
be the temperature of the spare sensor.
Power Failures
Checking Sensors
DO NOT REMOVE SENSORS FROM EVAPORATORS FOR CHECKING.
Use the monitor button to display the value the sensors are reading
on the LED (suction temperature
SCt , defrost temperature dFt , or
room temperature). Compare this value to the measured value with
a thermometer at each of these points. If they do not match, change
the sensor.
OR
The sensors can be checked for their proper operation by placing it
in a cup of ice water. Stir the ice water and measure the resistance
of the sensor. At 32°F the resistance should be 32,650 ohms. If it is
higher or lower by 1,000 ohms approximately, the sensor should be
replaced.