11
AIRFLOW & DEFROST
SUCTION
SUCTION
LINE TEMP
LINE TEMP
READING
READING
TXV
TXV
BULB
BULB
SUCTION
SUCTION
PRESSURE
PRESSURE
READING
READING
Fig. 1
Obtain pressure and temperature readings
AIR FLOW & PRODUCT LOAD
It is important that you do not overload the food product dis-
play so that it impinges on the air fl ow pattern—overloading
will cause malfunction and the loss of proper temperature
levels, particularly when discharge and return air sections
are covered. Please keep products within the load limit
line shown on the diagram below (Fig.1
).
DEFROST & TEMPERATURE CONTROLS
The refrigeration cycle is simply turned off by the case
controls for a specified amount of time; therefore, there are
generally no active defrost components utilized.
The discharge air probe monitors the temperature of the
discharge air and may be used as the defrost termination
sensor. The probe can generally be found behind the rear
baffle, in the upper baffle, or in front of the honeycomb.
NOTE: if the discharge air probe is used for defrost termi-
nation, none of the termination sensors listed earlier will be
installed in the case.
For more detailed information on
suggested defrost
times and settings, see
$SSHQGL[ $
.
Further adjustment
may be required depending on store conditions.
DETERMINING SUPERHEAT
To identify the correct superheat settings, complete the fol-
lowing steps:
Obtain
suction pressure from the access port. Obtain
the suction line temperature from the area near the
TXV bulb at the outlet of the evaporator coil (Fig. 1
).
Using the suction pressure reading and the Sporlan
®
temperature-pressure chart (
Appendix
&
), convert
pressure-to-temperature.
Finally, subtract the converted temperature reading
from the actual temperature reading. The resulting
number is the superheat setting—once this has been
determined, adjust the TXV as needed to obtain the
proper setting.
RETURN
AIR
DISCHARGE
AIR
AIR FLOW
LOAD
LIMIT
Fig. 13 Airflow
Summary of Contents for VNRB
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