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UV-SVP01A-EN 51
Troubleshooting
Safeties
Freeze Protection
The Tracer ZN.520 controller has
two methods of freeze protection.
1. An optional binary freezestat
that is wired to a binary input.
The freezestat is a capillary
tube type and is factory set to
35°F. When this device opens,
a “Low Coil Temp Detect”
diagnostic is generated.
2. Using the discharge air tem-
perature sensor, if the dis-
charge air temperature falls
below the discharge air low
limit, the controller increases
the heating capacity to temper
the air. If the discharge air
temperature remains below
the discharge air low limit for
3 minutes, the controller gen-
erates a “Low Coil Temp
Detect” diagnostic.
Fan Failure
A “Low Air Flow—Fan Failure” di-
agnostic is generated when a fan
status device is present and fails to
close after 1 minute of unit start-up
or when it opens for more than 1
minute during normal unit opera-
tion.
Space Temperature
Failure
If the Tracer ZN.520 has validated
a space temperature input and
then the input becomes invalid, a
space temperature failure diag-
nostic occurs.
Entering Water
Temperature Failure
If the Tracer ZN.520 has validated
an entering water temperature in-
put and then the input becomes in-
valid, an entering water temp-
erature failure diagnostic occurs.
Discharge Air
Temperature Limit
When the discharge air exceeds
the high or low limit setpoint and
the unit can not correct it by alter-
ing capacity, a “Discharge Air
Temp Limit” diagnostic is generat-
ed.
Outdoor Air Temperature
Failure
If the Tracer ZN.520 has validated
an outdoor air temperature input
and then the input becomes in-
valid, an outdoor air temperature
failure diagnostic occurs.
Humidity Input Failure
If the Tracer ZN.520 has validated
a relative humidity input and then
the input becomes invalid, a hu-
midity input failure diagnostic oc-
curs.
CO
2
Sensor Failure
If the Tracer ZN.520 has validated
a CO
2
input and then the input be-
comes invalid, a CO
2
input failure
diagnostic occurs.
Generic AIP Failure
If the Tracer ZN.520 has validated
a generic analog input and then
the input becomes invalid, a ge-
neric analog input failure diagnos-
tic occurs.
Defrosting-Compressor
Lockout
The defrost stat used with Tracer
ZN.520 on DX units is wired in se-
ries with the condensing unit.
When it opens to indicate a frost
condition, the Tracer ZN.520 sens-
es the open circuit and de-energiz-
es the condensing unit output. A
defrosting diagnostic is generated
at this point.
Maintenance Required
Note: If power to the unit is
cycled or discontinued for any
reason, all maintenance timers
are automatically reset.
The “Maintenance Required” di-
agnostic is generated when the fan
run-time exceeds the configurable
limit. This diagnostic is useful for
filter change notification.
Local Fan Mode Failure
If the hardwired fan mode input to
the Tracer ZN.520 controller is
present and then becomes invalid,
a local fan mode failure diagnostic
is generated.
Local Setpoint Failure
If the hardwired setpoint input to
the Tracer ZN.520 controller is
present and then becomes invalid,
a local setpoint failure diagnostic
is generated.
Generic Temperature
Failure
If the Tracer ZN.520 has validated
a generic temperature input and
then the input becomes invalid, a
generic temperature input failure
diagnostic occurs.
Invalid Unit
Configuration
If the Tracer ZN.520 has been con-
figured improperly or loses its
configuration, an invalid unit con-
figuration diagnostic is generated.
The unit must be re-configured
with a valid configuration to cor-
rect this problem.