Produce / Ice Cream - Continuous Run

Not everything HAS to be continuous. Ice cream is frozen. Usually -10. If you are hauling it in the winter and it is very cold outside you can get away with cycle. In the summer you will probably burn less fuel to have it on continuous. As for the produce - you will learn what is more sensitive to temperature than other products. For example, your berries, strawberries, blueberries, etc, and also your leafy greens, lettuce, parsley, etc, most run at 34, you should keep that on continuous. Apples, no big deal if they swing from 33 to 38. Bananas must be kept at about 60 continuous, something to do with they absolutely have to have the flow of air. Also have heard but never experienced places that will reject bananas if the pallets are touching the reefer walls. Only heard that from one driver. Generally, the "heartier" a product is the more ok it is if you run it on cycle.

 

I should also add that it is a dispatcher's way to cover their rear should something go sideways with the load. Most of them just don't know any better. Whatever, if they are paying the fuel and maintenance bill more power to them.

 

Our small fleet just purchased our first reefer. It has a 2008 TK SB-210. On continuous mode, the unit alternates between heat and cool and the the temperature fluctuates two degrees above and below the set point. For example, if the temperature is set at 55F, then the unit will keep the temp between 53 and 57 by alternating between heat and cool. Is that a normal interval or is it necessary to keep the temperature band tighter for certain things? For example, for lettuce at 34F, I would think dipping down to 32F would be problematic. Thoughts?

 

Then you set the temp a little higher to keep the band above freezing. If your concerned about the recvr then stop 5 minutes out and set where specified. I don't believe you can tighten the temp band. It's just not that good.

When I loaded Baskin Robbins the box had to probe zero before loading and it trucked at -20.

JMO

 

On a recent load of tomatoes at 55F they specified continuous mode. I guess they needed consistent air flow or the broker just wanted make sure the reefer was running all the time.

 

Tomatoes are good 55-60. As for when you set things on 33 or 34 on the thermo king units, the unit will actually try to push the air out at exactly 34 degrees, it will not just blast in below freezing air. This is what my reefer mechanic told me at least. It should not ever freeze the top layer if you put it on 34 continuous.

 

The reason for continuous on produce is that the product is still ripening and producing heat internally (and was likely loaded a bit warmer than they want you to haul it,) and if you run on cycle the center of the load can overheat and/or overripen in transit. Continuous does also keep the temp in a tighter range than cycle.

 

Yep, many produce items continue ripening after they are picked. A cross country trip you can evaporate as much as 800 lbs water off your load. They also give off methane. Not only do you want to keep the temp within +/- 2 degrees you want to keep circulation to pull out the excess evaporation or you speed up the ripening process. You also have to consider the outside temp and compensate accordingly to maintain the perfect pulp temp. Hot extremes you might go 2 degrees lower as cold extremes you might go 2 degrees warmer.

A little ice cream 101. It's not going to matter so much cycling or continuous because at them low temperatures your reefer is going to be screaming to maintain the low temps. Again air circulation helps you maintain a more constant temp. With continuous your reefer can go into defrost cycle or your unit can freeze over. Especially in a humid climate.

Ice cream is little ice crystals and must maintain minus temps to maintain it's crystal shape. When you get up around 10-20 degrees the crystals start becoming larger and the ice cream becomes more grainy. The crystals also start forming outside the packaging. You can tell if a driver let his load warm up that way. If you show up to deliver with iced over containers eyebrows will rise.

From my experience you can get away with -5 and not change the ice cream's properties. But you do what the customer wants because they don't want you riding that fine line. If they want -20 that's what you shoot for. I've had some old reefers that would fight just to get to -5 and never got rejected.