Buying a new reefer unit for hauling ice cream.

You know what is kind of odd, the refrigeration unit is what matters, not the trailer.

AND another odd thing - they all are supposed to hold -15 to -20 degrees.

If you are having issues with cool downs, maybe it is time to have the unit looked at or maybe the trailer is too old. The insulation does lose its effectiveness as time goes on.

 

This is just not right. Anything below 0 F, the ability to keep cold in and heat out becomes as critical as the ability to chill the space. And as set points get lower, this becomes exponentially more important.

Deep freeze loads need to be able to keep heat rise to a minimum when the unit cycles off.

 

I understand what you are saying, but the units are designed to hold temps in an insulated environment -15 to -20 degrees. I am not saying that you can put a refrigeration unit in a dry van and have it happen but in an reefer trailer, it should not have problems holding low temps.

The age of the trailer matters too, the heat transfer from outside to inside through conductivity seems to happen faster in an older trailer than it does with a new trailer.

Yes I understand that, the problem is when the trailer isn't moving it has a heat soak from the ground, one from the sun and one from the temps. This all factors into the rise rates.

As I mentioned the age of the trailer matters, there is a break down of the ability of the insulation to keep the heat transfer low while allowing the refrigeration unit to maintain the temps without constantly running.

 

The trailer matters,the reefer matters,the way it was loaded matters and the temperature outside matters.

 

You could do an ice cream spec reefer, most manufacturers have a similar spec, or you could say I want 4” insulation all over. If you will haul only ice cream, and by only I mean only then go for a heavy spec. If you’ll be hauling other commodities, the beefier the spec the less flexibility the trailer has.
In my situation I have to have the ability to get 30 pallets on. It is common for me to be in that situation. That means I can’t have more than 2” in my walls but I can increase to 3” in the floor and ceiling to add some efficiency.
The floor and ceiling inches aren’t a big deal for reefer but I’d be careful what you put in the walls or you may have issues loading things other than ice cream.
A Carrier 7500 or a TK S700 would be your options for heavy deep frozen applications.
I would also spec it with no produce vents and delete the front gutter and drains. The fewer intrusions into the interior, the better the efficiency. Use composite scuff liners and no aluminum scuff on the doors to reduce heat transfer.