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XT-70 Control Panel 44
E2 Parameters Definition:
will cause the overall system performance to become faster.
KI_1 Refrigeration integral gain. The default value is 4. The integral gain produces
an error based on small errors over time. Increasing this value will cause the
small error to be amplified over time, leading the system to be more sensitive to
small errors.
KD_1 Refrigeration Derivative gain. The derivative is produced by a sudden change
in the error. If the temperature is several degrees above setpoint, the PID will
ramp quickly. The error may not change much until the refrigeration reaches a
given level. At this point the temperature would drop quickly. The derivative
acts like a brake and will offset the error when large changes are being made.
If the temperature over shoots at start up, you would want to increase this
value. The default setting is 10.
UPDATE_T1 This value is in 1/10’s of a second, and determines when the PID loop is
updated. The default value is 100. Increasing this value will slow down the
entire loop. Decreasing will cause the loop and response to speed up. A value
which is too low will cause the system to cycle around the setpoint.
SCALE This value is used initially for testing and is the over all scaling for the PID
response. The default setting is 3. This is an engineering variable and should
normally not be changed.
THRESH This is the switchover point for the KI divisor. The default setting is 50. This
is an engineering variable and should normally not be changed.
ROL_DIFF Refrigeration operating level differential. This is a differential that is used for the
minimum operating level. When the refrigeration output raise above the
minimum setting plus the ROL_Diff, the ARL will shut off. The default setting
is 10 percent.
DOOR_TIME: Door open time. This time, in seconds, will determine the door position. This
value is determined by timing the door open cycle and the door closed cycle.
The two values should be averaged. The default setting is 180 seconds.
REF_LEVEL: Refrigeration minimum operation level. The system will uses the fresh air doors
to maintain a minimum operating level. This will keep the refrigeration from
short cycling under light loads and also provides a constant CO
2
purge. The
default setting is 30 percent.
LOW_CUTOUT This is the point below setpoint where the ARL shuts off and allows the refrig-
eration PID loop to go to 0. This is a safeguard if the plenum temperature
drops the setpoint this amount because the OSA is not warm enough. The
setting is in .1 of a degree and the default setting is 5 or .5°
CO2_RAS / BURNER START: CO2_Ras purge rise above setpoint. If the plenum rises above setpoint this
amount during refrigeration, the doors will be blocked from opening any further.
This value is in 1/10’s of a degree. The default setting is 5 or .5°.
Burner Start is a Onion parameter. This is the percentage that the gas valve
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