Door And Perimeter Temperature Calibration; Door And Perimeter Heater Duty Cycle Automatic Control - NuAire NU-5510 Operation And Maintenance Manual

9.2

Door and Perimeter Temperature Calibration

The DHD Autoflow's inner glass door and outer shell perimeter temperature calibration is best
accomplished by running the Incubator 24 hours with the water pan in place and perform the following
calibration sequence, if required. Open the Incubator door and look for general condensation. Some
condensation on the glass door can be desirable as an indication of adequate humidity in the chamber.
Typically, one to two inches of condensation in the corners of the glass door indicates a properly calibrated
door heater. The perimeter heater is the heater located on the outer shell next to the glass door. Typically,
no condensation should form on the inner chamber next to the glass door. However, if calibration is
required, simply perform the procedure as stated below. The door and perimeter heater operates as a duty
cycle percentage ON/OFF (0 is off, 100 is Full ON). Typically, 14 to 22 percent is the most effective duty
cycle for the door heater and 30% to 40 % for the perimeter heaters in 22ºC ambient with a 37.0ºC set
point. Default settings are 18% for the door and 32% for the perimeter.
The following steps should be taken for setting these duty cycle percentages:

Allow Incubator to stabilize at its given temperature and humidity level in run mode.

Press "SEL" to indicate LED next to temperature display.

Press and hold ▲ and ▼ keys simultaneously for three seconds. Temperature display alternates
between either "dor" or "PEr" and the duty cycle percentage.

Press ▲ or ▼ key to desired "dor" or "PEr" duty cycle percentage (press RUN/SETUP key to change
from "dor" to "PEr" and back again). A maximum adjustment of 2% for the door and 4% for the
perimeter heaters should be made at a time.

Press "SEL" to set current value and exit calibration.
9.2.1

Door and Perimeter heater duty cycle automatic control

The door and perimeter duty cycles are automatically reduced when the room temperature in the
lab increases enough to allow the contribution from these heaters to overheat the chamber. For
example if the door and perimeter duty cycles are set up when the room temperature is 22ºC and
the room temperature is allowed to increase to 27ºC. Less heat is required to keep the chamber at
set point. If the chamber starts to overheat, the duty cycles will be reduced at a rate of 1% per
minute starting when the chamber temperature is 0.2ºC above set point. The duty cycles will
continue to be reduced until the chamber temperature returns to set point. These duty cycles are
continuously monitored and will be increased slowly again, as long as the chamber temperature
does not go over the set point. If the room ambient reduces back to 22ºC the door and perimeter
duty cycles will actually be returned to their original settings.
Note: If it is known that the lab room temperature where the Incubator is installed will vary
significantly. (For example, the heater or air conditioning is shut off after work hours or there is
no air conditioning and the room temperature has large temperature swings.) The door and
perimeter duty cycles should be set in the lower temperature expected in the lab. Then the door
and perimeter heaters will automatically be adjusted to avoid over temperature conditions in the
chamber when the room temperature rises. In this case the chamber should be monitored for
condensation regularly. If the chamber walls and ceiling start to get excessive condensation the
door and perimeter heater duty cycle settings will need to be reduced. Do not adjust the duty cycle
settings by more than 2% on the door heater or 4% on the perimeter heater at a time.
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