Carrier 69NT40-541-001, Operation And Service

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T-316 5–8
5.9 OBSERVE UNIT OPERATION
5.9.1 Crankcase Heater
When the crankcase heater is installed, it will be operational whenever the compressor is off and there is power to
the unit. The heater is connected to a set of normally closed auxiliary contacts on the compressor contactor.
5.9.2 Probe Check
If the DataCORDER is off, or in alarm mode the controller will revert to a four probe configuration which includes
the DataCORDER supply and return air probes as the secondary controller probes. The controller continuously
performs probe diagnosis testing which compares the four probes. If the probe diagnosis result indicates a probe
problem exists, the controller will perform a probe check to identify the probe(s) in error.
a. Probe Diagnostic Logic - Standard
If the probe check option (controller configuration code CnF31) is configured for standard, the criteria used for
comparison between the primary and secondary control probes is:
1°C (1.8°F) for perishable set points or 2°C (3.6°F) for frozen set points.
If 25 or more of 30 readings taken within a 30 minute period are outside of the limit, then a defrost is ini-
tiated and a probe check is performed.
In this configuration, a probe check will be run as a part of every normal (time initiated) defrost.
b. Probe Diagnostic Logic - Special
If the probe check option is configured for special the above criteria are applicable. A defrost with probe check will
be initiated if 25 of 30 readings or 10 consecutive readings are outside of the limits.
In this configuration, a probe check will not be run as a part of a normal defrost, but only as a part of a defrost initi-
ated due to a diagnostic reading outside of the limits.
c. The 30 minute timer will be reset at each of the following conditions:
1. At every power up.
2. At the end of every defrost.
3. After every diagnostic check that does not fall out side of the limits as outlined above.
d. Probe Check
A defrost cycle probe check is accomplished by energizing just the evaporator motors for eight minutes at the end
of the normal defrost. At the end of the eight minute period the probes will be compared to a set of predetermined
limits. The defrost indicator will remain on throughout this period.
Any probe(s) determined to be outside the limits will cause the appropriate alarm code(s) to be displayed to identify
which probe(s) needs to be replaced. The P5 Pre-Trip test must be run to inactivate alarms.
5.10 SEQUENCE OF OPERATION
General operation sequences for cooling, heating and defrost are provided in the following sub-paragraphs. Sche-
matic representation of controller action are provided in
Figure 5.3 and Figure 5.4 . Refer to Section 4 for detailed
descriptions of special events and timers that are incorporated by the controller in specific modes of operation.