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BTU VENTILATION CORPORATION
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OFFICE 888-884-8070
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FAX 218-346-7485
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www.btucorp.com
XT-70 Control Panel
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ONION SUPPLIMENT:
The XT Panel can be either a Potato panel or an Onion panel by loading the correct software. This supplement
will explain the differences in the Onion Logic and panel layout. The HMI (color touch screen) will automatically
change depending on if it sees a potato or onion panel. For the Onion panel the some of the manual, off, Auto
switches changes. The Heat switch needs to be relabeled Heat, Aux 1 relabeled to Dehumid and the Aux 2
relabeled to Cure.
This shows the HMI layout, the actual switches on the panel need to be relabeled.
The Onion panel operates in two distinct modes, Cure or Cooling. In the Cure mode the panel is looking for
OSA temperatures greater than the Start Temp. In the Cooling mode the panel is looking for OSA tempera-
tures less than the Start Temp. The Cure mode is the initial drying mode of the crop, that the system must be
placed in following harvest. It usually runs at a higher temperature than is customary with a low humidity.
Cure Flow Chart Explanation:
Please refer to the CURE MODE flow chart for the following explanation. To enter the Cure mode the CURE
switch must be in Auto. The run time clock must be set to RUN for the desired cure times. At this point the
panel will look at the OSA temperature, if it is above the Start temperature it will try to cure the onions naturally
using the warm dry outside air.
OSA > START TEMP The OSA Diff setting will affect the Start temperature and a suggested setting would be
+3 to insure warm enough outside air. If the OSA temperature is less than the Start temperature then the panel
will go to the Burner mode. The Burner mode will be covered later.
CPH < HMAX
The outside air must also be dry enough. The CPH is calculated plenum humidity.
The CPH is calculated by taking the outside air temperature and humidity and figuring out what the new value
will be when mixed with the return air and warmed to the plenum temperature. Raising the temperature of the
outside air will lower the relative humidity content. In this case we will be using 100% outside air and the CPH
will roughly be the outside humidity. The HMAX is set to the operators preference, a typical setting would be
60%. Thus if the outside humidity was less than 60% the system would determine that the air is dry enough. If
the outside humidity was greater than HMAX then the system would have to go to the BURNER mode.
BURNER
DEHUMID
CURE
9.0
9.1
