T-292
4-5
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 initi-
ated 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
initiated due to a diagnostic reading outside of the limits.
c.The 30 minute timer will be reset at each of the follow-
ing 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.
4.10 SEQUENCE OF OPERATION
General operation sequences for cooling, heating and
defrost are provided in the following subparagraphs.
Schematic representation of controller action are
provided in Figure 4-3 and Figure 4-4. Refer to Section
3 for detailed descriptions of special events and timers
that are incorporated by the controller in specific modes
of operation.
SET POINT
PULL DOWN
RISING
TEMPERATURE
--0.5
_
C
(0.9
_
F)
--0.20
_
C
+.20
_
C
HEATING
HEATING
AIR CIRCULATION
+2.5
_
C
(4.5
_
F)
UNLOADED OPERATION
MODULATED
COOLING
UNLOADED
AIR CIRCULATION
SET POINT
+.20
_
C
HEATING
+2.5
_
C
(4.5
_
F)
FALLING
TEMPERATURE
MODULATED
COOLING
UNLOADED
--0.5
_
C
(0.9
_
F)
AIR CIRCULATION
NOTE: TEMPERATURES INDICATIONS ARE ABOVE OR BELOW SET POINT
START UNLOADED,
TRANSITION TO
ECONOMIZED
OPERATION
--0.20
_
C
Figure 4-3 Controller Operation -- Perishable Mode
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Summary of Contents for 69NT40-531 Series
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