February 17, 2016

Deciphering the download/printout from a Trailer Refrigeration Unit Download (TRU)

By: Tom Oliveri

When in transit temperatures may be a factor with your shipment failing to meet contract at destination, there are several key factors to review and ascertain what may have caused, or contributed to the situation. Three major components for review are: 1) pulp temperatures of the produce at origin and at time of loading,  in comparison to the pulp temperatures reflected at destination on the government inspection, 2) the portable temperature recording device placed inside the trailer at shipping point and 3) the carrier’s download of the smart reefer unit.  Today’s blog focuses on the third component, the carrier’s smart reefer download.

When reviewing a carrier TRU download report there are designated columns on the printout that will assist you in determining if the refrigeration unit was operating consistent with the bill of lading instructions provided to the carrier at shipping point.

While the download report format may vary based on the manufacturer of the Trailer Refrigeration Unit (TRU), the printout report will contain essential information that will highlight any anomalies your produce was subjected to while in transit.

Here are a few of the basics. 

The report as shown in the sample has several columns; however we are only focusing on columns 1, 2, 3, 4, 5, 6 and 9 as these columns indicate the time and temperature environment.  Click here to view a sample download report.

Column 1 – Time: This denotes the start date and time of temperature monitoring
Column 2 – Set Point: This will indicate the temperature set point, and be sure that it matches your requested temperature instructions on the bill of lading.
Column 3 – Return Control: This is measuring the actual trailer air temperature as it returns to the intake refrigeration unit after circulating through the trailer
Column 4 – Return Display: This is the air temperature reported on the control panel visible to the driver, and should be at or near the temperature shown in column 3
Column 5 – Discharge Control: This is reporting the actual temperature originating from the TRU
Column 6 – Discharge Display: This is the supply air temperature reported on the control panel, which is a visible display to the driver, and should be at or near the temperature shown in column 5
Column 7 – Ambient:      This is the outside temperature
Column 8 – Coil:  
Column 9 – Op Mode: This discloses the operational mode for the TRU. Most critical to review is if the refrigeration unit is running continuous or on a start/stop mode. Fresh produce should only be transported under continuous cycle.
Column 10 – Suction Pressure:   
Column 11 – Discharge Pressure:   
Column 12 – ETV Position    
Column 13 – Engine RPM:     
Column 14 – Engine Temperature:  

The first thing to confirm is if the set point that you requested remained unchanged throughout transit.  Next check the discharge control to see if the air temperature being supplied is within an acceptable tolerance of the set point. Compare the return control air temperature, which is the circulated air returning to the refrigeration unit to confirm that it is within a reasonable tolerance of the supply air.  Confirm whether or not the Op mode was set to continuous and not start/stop.  Start/stop start mode should never be utilized on fresh produce.

This information is provided only as a general explanation, as there may be other technical factors to consider, and may require further consultation in many situations.   

Should you need any guidance interpreting a TRU download or need additional information, please do not hesitate to contact me directly at 949-885-2269, or Ken Gilliland, Western Growers Director of Transportation and International Trade at 949-885-2267. Should you have any questions on this topic or any other matter, please contact me at 949-885-2269 or TommyO@wga.com.