Accurate and Steady Wins the Delivery

Let’s get the New Year started with the right temp!! Although it’s cold outside for most of us and we are eagerly awaiting the return of those sunny & warm days, we can control some of the temperatures we deal with on a daily basis. That’s right, the setting of reefer running temperatures!!!

This is a topic we like to revisit on a regular basis, as the impact of improper reefer temperature settings and operations can be severe. So, let’s review:

The Basics:

- All refrigerated trailer units have a SET POINT; this sets the temperature inside the unit, and the number is indicated on the reefer’s SET POINT digital display.

- Reefer unit operators have to physically set the temperature of their trailer, and must also select the MODE that the reefer unit will operate in.

- There are two temperature modes a refrigerated trailer can run on: CONTINUOUS or CYCLE-SENTRY.

Continuous:

- Continuous air flow means that there is a consistent temperature through the trailer for the duration of transport.

- This setting MUST be used for ALL produce loads.

- Produce loads need continuous air flow to handle the heat produced by product respiration.

- Temperature recorder devices can indicate if a refrigerated trailer has been set to continuous. How? Take a look:

Cycle-Sentry:

- Cycle-Sentry is a START-STOP setting, so air flow for the refrigeration unit is not constant.

- When the temperature inside the refrigerated trailer drops between 0.5F and 1F below the SET POINT, the refrigeration unit will TURN OFF. The unit then waits until the temperature inside the trailer warms up 5F above the SET POINT, and then turns back on.

- This setting should only be used for frozen loads (loads that are intended to ship cooler than 24F).

- Produce loads should NEVER BE RUN ON CYCLE. Cycle cannot manage the heat produced by product respiration, and will expose the product to damage.

- Running a produce load on cycle-sentry greatly increases your exposure to claims and additional charges.

- Temperature recorders can also indicate if a shipment has been run on cycle-sentry. How? Take a look:

So there we have it, proof of the importance and necessity of running produce loads on CONTINUOUS. Also, it is important to regularly check the fluids in the refrigeration unit to make sure it will operate as designed. Keep the refrigerated trailer on its regular maintenance schedule to ensure all settings are accurate and will work as designed.

References:

4 Steps to a Successful Shipment. Sensitech Cold Chain Visibility. Powerpoint Presentation. Received on 11/08/2009, Accessed for document on 12/01/2012.

Setting the Temp

Refrigerated trailer temperature settings are critical to understand in order to ensure the success of any perishable shipment. All refrigerated trailer units have a “Set Point” that sets the temperature inside the trailer, and this number is shown on the reefers Set Point digital display. Drivers have to physically set the temperature of their refrigerated trailer, and must also select the “mode” that the reefer unit will operate in: continuous or cycle-sentry. Understanding the two different reefer trailer temperature setting options (continuous vs. cycle-sentry), along with what needs to be done to ensure that a produce load will maintain temperature while in transit is key.

Now, let’s explore the difference between the two refrigerated trailer temperature mode settings:

Continuous Setting:
This setting MUST be used for ALL produce loads; they need continuous air flow to handle the heat of product respiration. Continuous air flow means that there is a consistent temperature throughout the trailer for the duration of transport. Temperature recorders can indicate if a trailer has been set to continuous or cycle-sentry. Below, an example of a temperature recorder printout that indicates a shipment has run on continuous:

Cycle-Sentry Setting:
This setting should only be used for frozen loads (i.e. loads that are intended to ship cooler than 24F). Frozen loads can handle more significant temperature variances without causing damage to the product. The cycle sentry setting is a START-STOP setting, so air flow for the refrigeration unit is not constant. When the temperature inside the refrigerated trailer drops between 0.5 and 1F below the Set Point, the unit will turn off. The unit then waits until the temperature inside the trailer warms up 5F above the set point temperature, and will then turn itself back on. For this, reason, produce loads should NEVER be run on cycle!!!! Running a produce load on cycle-sentry greatly increases your exposure to claims and additional charges!!!

Temperature recorders can also indicate if a shipment has been run on cycle-sentry. Below is an example of a temperature recorder printout in this setting:


Some other points to remember:
• Make sure to check the fluids in the refrigeration unit to make sure it will operate as designed.
• Keep the refrigerated trailer on its regular maintenance schedule to ensure all settings are accurate and will work as designed. Preventative maintenance is the best kind!!!
• Pre-cool the trailer to ensure all residual heat inside the trailer walls, floor and ceiling is eliminated prior to loading. This is especially important during these summer months!!!


Have anything else to add? Please share!!!

References:
4 Steps to a Successful Shipment. Sensitech Cold Chain Visibility. Powerpoint Presentation. Received on 11/08/2009, Accessed for document on 21/07/2011.

Continuous vs. Cycle Sentry

Refrigerated trailer temperature settings are one of the most critical aspects that can influence fruit and vegetables products upon delivery. Below is a description of both settings and further information on their functions:

Continuous:

Continuous setting must be used for produce loads, as they need continuous air flow to handle the heat of product respiration. Continuous air flow allows for more consistent temperature throughout the trailer for the duration of transport. All reefer units have a ‘Set Point’. For example, if you have a set point of 33°F, the temperature reading displayed by the set-point will stay constant on a smart reefer download. On continuous setting, the reefer has a set defrost cycle (definition: Defrost cycle – the process of removing ice or frost buildup from a coil). The intervals are factory set for every 6 hours, but the unit will auto defrost based on a temperature difference across the coil. The defrost cycle can be changed to compensate for produce that has higher heat respiration, for higher ambient temperature (definition: Ambient temperature - the certain temperature within an enclosed space), and for door openings. For example, if it is a humid day and the driver is doing a lot of door openings, you may need to have a more frequent number of defrost cycles. Although the reefer has this defrost cycle on continuous setting, it does not change the product temperature due to the fact that most reefers have a very high heating capacity (definition: Heating capacity – The amount of heat energy needed to raise the temperature of a given mass of a substance by one degree Celsius). The temperature in the air of the reefer will heat at a faster rate than the temperature of the product that is in the trailer. The time of a defrost cycle is not is significant enough to affect the product temperature.

Below is an example of a temperature recorder printout for a reefer in continuous mode (note spike at end of 41°F is at unloading point:

Cycle Sentry:

Cycle-Sentry setting should only be used for frozen loads, i.e. loads that are intended to ship colder than 24°F. Frozen loads can handle more significant temperature variances without causing damage to the product. On cycle-sentry, the load also has a ‘Set Point.’ For example, if you have a set point of 22°F, the set-point will also stay constant on the download, as it does on continuous setting. However, when the ambient temperature in the reefer drops to between .5 to 1 °F lower than the ‘Set Point’ (in this case that would be 21.5°F), it turns off. It then waits until temperature warms up 5°F past the set point (in this case, 27°F), and then turns itself back on.

Below is an example of a temperature recorder printout for a reefer in cycle-sentry mode:




Conclusion:

Produce loads should not be set on cycle-sentry, and the only benefit of operating on this setting is significant fuel savings. Because the temperature of a load on cycle-sentry can vary dramatically during the time of transport, this can cause freezing on top boxes or condensation in packaging.

Reference:

4 Steps to a Successful Shipment. Sensitech Cold Chain Visibility. Powerpoint Presentation. Received on 11/08/2009, Accessed for document on 01/06/2010.