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Remedy
Close door to the box. Make sure door remains closed unless/until access to box is needed.
Verify at controller display the current superheat and valve position; go to
Status →Superheat/EXV Current Pos.
If superheat is
consistently high and valve is consistently running at or close to 100%, the system could be low on refrigerant. Verify if sight
glass at condensing unit is clear. Verify suction pressure with a set of gauges. Recharge system as needed, verify if any leaks are
present and fix as needed.
Verify at condensing unit if compressor is shutting down intermittently. Troubleshoot condensing unit and verify if high head
pressure, phase loss, etc.
Verify under the controller settings that the correct refrigerant is selected. On the display, go to
Settings →Equipment→Refrigerant
. An incorrect refrigerant setting will cause incorrect superheat calculation and the system
will not operate properly.
Verify if Suction Temp Thermistor alarm is active: on controller display go to
Service →Current Alarms
. Also verify Suction
Temperature reading under
Status→Sensors→Suc on Temp
; if it is reading "‐60 ⁰F", the sensor is not making good contact or is
missing. If Suction Temp sensor input is missing, the EXV will remain at a fixed position until sensor is replaced, and alarm
"A100 Suction Temp Thermistor Failure"
will be active. If sensor is reading a value other than ‐60 ⁰F, verify that it is not an
erratic value and that the reading reasonably corresponds to the conditions at the evaporator (for example, if sensor is reading
150 ⁰F when the suction line at the evaporator is near freezing conditions). Replace Suction Temp Thermistor (part no.
08219637).
Verify if Suction Pressure alarm is active: on controller display go to
Service →Current Alarms
. Also verify Suction Pressure
reading under
Status→Sensors→Suc on Pressure
; if it is reading "‐14.7 PSIG", the sensor is malfunctioning or is disconnected.
If the controller detects that the pressure input is missing, alarm
"A106 Suction Pressure Sensor Failure"
will be active and the
controller will attempt to calculate approximate superheat by using Evap Temp 1 reading instead of Saturated Suction Temp and
continue metering the EXV, but the calculated superheat will not be as accurate. Replace Suction Pressure Transducer (part no.
08219621).
Verify harness connection to the EXV and to the controller board is secure. Set System Enable to NO, under
Settings →System
Enable
in order to close the EXV and force a pumpdown. Confirm that the EXV can be heard moving as it closes. Confirm EXV
position under
Status→EXV→EXV Current Pos.
is 0%. Verify that compressor pumps down and shuts off after a couple of
minutes; Suction Pressure reading under
Status→Sensors→Suc on Pressure
should decrease as the system pumps down. If
the compressor is still running and does not turn off, the EXV may be malfunctioning and allowing some refrigerant to pass
through even after being commanded by the controller to close. See
Addendum A
for more information on troubleshooting the
EXV. Replace EXV if necessary.
Make sure door to the freezer is kept closed unless/until access to freezer is needed.
Verify that when controller starts a defrost, the heaters are energized and operating properly. A manual defrost can be started
by going on the display to
Service →Defrost Control→Start a Defrost
. Verify at the controller board that the LED's for the
defrost relays turn ON and their status is ON on the display (
Status→Outptus→Defrost Relay #1/#2
).
If the unit is a Low
Profile evaporator, make sure that Coil Type is set to "Single"
(go to
Settings→Equipment
and scroll down to verify these
parameters), and that Evap Temp 1 sensor is connected and having a valid reading. If Evap Temp 1 sensor is disconnected, the
controller will alarm (
"A101 Evaporator Temp Sensor Failure"
) and the Defrost Relays will not turn ON. If Coil Type is
mistakenly set to Dual, the controller will alarm (
"A102 Evap Temp 2 Thermistor Failure"
) and the missing Evap Temp 2 sensor
will prevent Defrost Relay #2 from turning on; this would keep the bottom heater and drain pan heater from turning on during a
defrost and will cause ice build up on the bottom part of the coil. If both Defrost Relays are turning ON, verify with a meter that
the heaters are drawing amps and are warming up; if they are not, verify the heater wiring with the wiring diagram at the
evaporator. If the heaters are wired properly but still not heating, they may need to be replaced.
If the heaters are verified to be working properly, proceed to verify defrost cycle duration: on the controller display, go to
Status →Defrost→Last Defr. Time
. Also, force a defrost and wait for it to finish to take note of the duration. Low Profile
Evaporators typically need between 20 to 30 minutes defrost duration to clear the ice. If the defrost cycle is too short, the
Defrost Termination Temperature (
Def. Term. Temp
) and Runtime Until Defrost (
Def. Cmp. Run Time
) can be adjusted as
needed in
Settings→Equipment
. Also, the pulsing on Defrost Relay #1 (top heater) can be disabled by setting
Defrost Pulse
Override
to YES if needed. If the unit already has some ice built up in the coil, it may take several defrost cycles to clear the ice
after the parameters mentioned above are adjusted.
Make sure door to the freezer is kept closed unless/until access to freezer is needed.
Verify that when controller starts a defrost, the heaters are energized and operating properly. A manual defrost can be started
by going on the display to
Service →Defrost Control→Start a Defrost
. Verify on the controller board that the LED's for the
defrost relays turn ON and their status is ON on the display (
Status→Outptus→Defrost Relay #1/#2
).
If the unit is a Center
Mount evaporator, make sure that
Coil Type
is set to
"Dual"
and
Defrost Pulse Override
set to
"YES"
(go to
Settings→Equipment
and scroll down to verify these parameters), and that Evap Temp 1 and Evap Temp 2 sensors are
connected and having a valid reading. If Evap Temp 1 sensor is disconnected, the controller will alarm (
"A101 Evaporator Temp
Sensor Failure"
) and Defrost Relay #1 will not turn ON; if Evap Temp 2 sensor is disconnected, the controller wil alarm (
"A102
Evap Temp 2 Thermistor Failure"
) and Defrost Relay #2 will not turn ON. If the Defrost Relays are turning ON, verify with a
meter that the heaters are drawing amps and are warming up; if they are not, verify the heater wiring with the wiring diagram
at the evaporator. If the heaters are wired properly but still not heating, they may need to be replaced.
On Center Mount evaporators (
Coil Type = Dual
), both Evap Temp 1 (white wires) and Evap Temp 2 (blue wires) are used for
defrost termination. During a defrost cycle, when Evap Temp 1 sensor reaches Defrost Termination Temp, the Defrost Relay #1
will turn off. Same for Evap Temp 2 with Defrost Relay #2; each side will terminate defrost independently. Verify with the
wiring diagram on the unit that Evap Temp 1 sensor is located on the coil whose heaters are wired to Defrost Relay #1. Same
goes for Evap Temp 2, it should be located on the coil whose heaters are wired to Defrost Relay #2.
On Center Mount evaporators (
Coil Type = Dual
), make sure that Defrost Pulse Override is set to YES so Defrost Relay #1 does
not pulse during a defrost cycle (go to
Settings →Equipment→Def. Pulse Overr.
and make sure it is set to YES).
If the heaters are verified to be working properly, proceed to verify defrost cycle duration: on the controller display, go to
Status →Defrost→Last Defr. Time
. Also, force a defrost and wait for it to finish to take note of the duration. Center Mount
Evaporators typically need between 20 to 30 minutes defrost duration to clear the ice. If the defrost cycle is too short, the
Defrost Termination Temperature (
Def. Term. Temp
)and Runtime Until Defrost (
Def. Cmp. Run Time
) can be adjusted as
needed in
Settings→Equipment
. If the unit already has some ice built up in the coil, it may take several defrost cycles to clear
the ice after the parameters mentioned above are adjusted.
Compressor could be shutting down
intermittently.
Verify that the correct refrigerant is selected.
Door is open.
Suction Temp sensor disconnected (controller will
alarm; red LED on controller will be blinking), or
sensor could be malfunctioning/reading erratic
value.
Suction Pressure transducer disconnected
(controller will alarm; red LED on controller will be
blinking), or transducer could be malfunctioning.
9
10
Suction line at compressor is icing up
excessively.
System could be undercharged/leak present in the
system.
12
Evaporator coil is icing up (Center Mount
FREEZER, electric defrost).
Unit is cooling but Space Temp never
reaches setpoint.
Verify that heaters are working when controller
goes into defrost.
Verify duration of defrost cycle/runtime between
defrosts.
Door is being left open.
11
Evaporator coil is icing up (Low Profile
FREEZER, electric defrost)
Verify EXV is functioning properly, closing
completely for pumpdown.
Verify Evap Temp 1 and Evap Temp 2 sensor
locations.
Verify Defrost Pulse Override is set to YES.
Door is being left open.
Verify that heaters are working when controller
goes into defrost.
Verify duration of defrost cycle/runtime between
defrosts.
Problem
Possible Cause
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