Emerson Control Link, Инструкция по установке и эксплуатации

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28 • Control Link ACC I&O Manual 026-4704 Rev 6
9 Operation
The Control Link ACC uses two algorithms for
modes of operation. For the standard mode of
operation, the Control Link ACC prevents moisture
accumulation by maintaining door frame temperature
based on the dewpoint and setpoint offset. The
alternate PMAC mode of operation can be configured
from the E2 and is also used under failure conditions
if no door frame temperature sensor is available.
Using the PMAC algorithm, the Control Link ACC
will calculate the heater ON time based on the
dewpoint temperature. The configuration has two
parameters: the first sets the lower dewpoint
temperature at which the heater will be OFF. The
second sets the upper dewpoint temperature at which
the heater will be 100% ON. A linear calculation is
made between those limits:
Heater ON% = 100%*(Current _Dewpt - DewptOFF)

(DewptON - DewptOFF)
The ACC monitors a board temperature near the
heater output driver to ensure that the heater driver
does not exceed its maximum temperature rating.
There is a back-off algorithm that will become active
once the monitored board temperature says the heater
driver is within 6°C (10.8°F) of the maximum
temperature rating. At 6°C (10.8°F) below the
maximum rating, the ACC will not let the heater
driver be ON more than 95% of the time. If the
temperature continues to rise and is within 3°C
(5.4°F) of the maximum rating of the heater driver,
the algorithm will not let the heater driver be ON
more then 90% of the time. The final step is triggered
if the heater driver is more than 2°C above its
maximum rating at which time the heater will be
turned OFF. This is the OVER TEMP failure
condition (see Section 10, Error Modes ). Once the
heat driver temperature drops 5°C (9°F) it will be
allowed to come back ON.
This back-off strategy will only come into affect if
the heater has to be ON 100%, you are running at the
maximum rated current, you are at maximum rated
ambient for the ACC.
9.1. Control Link ACC Status
LEDs
The Control Link ACC has four status LEDs that
indicate what the controller is doing. They are: the red
Heater Status LED (HEAT), the green General Status
LED (Status) and the two Network Status LEDs (red
transmit TX and yellow receive RX).
9.1.1. Heater Status LED
The Heater Status LED ( Heat ) glows red any time
the door heaters are ON, and is OFF when the heaters
are OFF.
Under normal operation, this LED should pulse
ON and OFF when no door sweat is visible, indicating
it is pulsing the heaters to maintain the necessary
amount of heat to prevent door sweating (given the
current dewpoint and case temperature). When a case
door is opened, the LED will remain ON for longer
periods of time (and may even remain ON without
pulsing) to compensate for the change in case door
frame temperature.
Note that it is possible for this LED to remain OFF
for long periods of time if the dewpoint is very low
(e.g., during dry winter days).
9.1.2. General Status LED
The General Status LED blinks green to indicate
the controller is powered up and functioning
normally, and whether or not there are any alarm
conditions.
If the controller is functioning normally, the
Status LED will blink once per second. If there is an
error condition, it will blink at different rates to
indicate the active error condition (see Section 10,
Error Modes ).
Figure 9-1 -
LED Locations