TD is the difference between the box air temperature and the refrigerant's saturated suction temperature (SST). A smaller TD generally means higher air humidity and better product preservation.
Low TD (6°F - 8°F)
Required for Freezers and high-humidity products (Produce, Floral).
Medium TD (10°F - 12°F)
Standard for general coolers (Dairy, Meat, Beverages).
High TD (15°F+)
For non-sensitive products or quick pulldown (lower capital cost).
The R-value measures thermal resistance. A higher R-value means lower heat loss (Transmission Load).