Reefer setting

My suggestion would be to buy a decent infrared thermometer. Check your load at the other end and modify your settings appropriately. I haul a dual temp trailer that is center divide and have a mix of frozen in the main and fresh dairy in the cooler side. For a couple hours even, a bit below freezing will not freeze dairy (produce is a little more sensitive due to surface moisture, it will freeze and you will have a claim on your hands). What I am finding is the input temp (reading you see on the display) may be saying 35F but that may not be true product temp. At this time of year I usually wind up raising a degree or 2 to maintain proper product temp (going into the store at 32F to 34F). Another note when using the thermometer is plastic wrap will degrade the accuracy of the reading and best to read from product. Keep a list of the temperature alterations if you find it necessary so you can modify your settings for any individual trailers if you see a big difference.

Finally, Carrier also is able to give an ABC for temp range like the TK.

 

Just because your box temp has some variance doesn't mean the product jumps up and down on cycle. It will maintain an average temperature. The reefer temp sensor is at the top of the box. With no airflow of course the top will be warmer as heat rises plus the sun shining on the box. When you have 3-4 feet thick of product on a pallet it takes several hours for the temperature to adjust. Never solely rely on what your unit says. Probe your product. An infrared is great for double checking the box temp and non-critical frozen items and items like boxed meat or other items in sealed boxes. Stuff like bananas and other produce you want to get your temperature probe out and get a core reading as fruit and vegetables are more sensitive to closer tolerances.

Produce the moment it is picked it continues it's ripening process to the point it starts decomposing. Melons and grapes are one fruit that is fully ripe once it's picked. During this ripening process produce is evaporating water and giving off gases. Not only are you trying to keep a more stable temp with airflow you are mixing the air evenly getting the gas concentrations off the product for a better environment. That's what a reefer is, a controlled environment. You are the controller. Just like a GPS you just don't set and go. You have to watch it and set accordingly. Does your refrigerator at home run continuously? No.

As a reefer driver know your product and what you can get away with. Basically produce is your only mandatory continuous running with a few exceptions. You always do what the customer wants. If the shipper tells you one thing and your dispatcher tells you another I'll call the receiver and ask what they want. After all they are the ones that accept or reject your product. Once you get more experience you'll learn each product and won't have to ask. Somewhere buried in this forum I have a USDA temperature chart one can use as a reference.

Take in consideration the outside temperature extremes. With extremes can modify your product temp as much as 2*. I remember one time sitting on bananas a weekend in -15 with around a -40 windchill I had to run 4* higher than normal. In extremes you want to keep your doors shut as much as possible but probing and recording temp will cover your butt. Something like bananas which the ideal temperature is 60* and you have an acceptance variance from 58* to 62* from the customer. So depending on the outside temp favor one end of the scale. Summer run 58*, Winter run 62* The more closer to 60* outside the closer to the 60* set point you get.

Ice cream is made of little crystals. About 5* them crystals start changing shape and become bigger crystals which the customer won't tolerate. That's what you want to avoid. You don't want to ride a fine line is why they want it down around -10*. I'm just telling you that so you know what you can get away with. Warm ice cream the container will frost over and tell on you.

Another thing you have to consider is do you have a temp recorder on board. Then you have to do what the customer wants and not what you know. If they want continuous and you know cycle will work you run on continuous because the recorder graph will either be a flat line or on cycle it will wave up and down. You can tell on it. Other than a few damaged boxes from others I have never lost a load. You'll hear all the time of whole loads getting rejected. Just take your time to ask and learn like you are now and you'll do just fine. Reefer product is like a game. Try to be good at it and you'll have self satisfaction of having the product right on the money.