901-10113 - 43 - 9/16/2024
9 Glossary
This glossary helps to explain terms used in the manual. Terms are defined in the context of truck
refrigeration with Cold Plates. Some terms have other meanings when used elsewhere.
Air Temperature vs. Product Temperature – The air temperature in the refrigerated compartment
may fluctuate greatly due to door openings and/or other factors. The product temperature generally
changes very slowly due to its mass. Air temperature being “too high”, even for several minutes,
usually has little effect on the product temperature.
Ambient Air Temperature – Temperature of the outdoor air surrounding the truck body.
Amp – Abbreviation for ampere, the basic measuring unit of electrical current.
Arcing – Electrical current passing through air, producing a bright “spark”. In Cold Plate systems,
arcing happens if AC power is unplugged without first turning the system OFF. Arcing can damage
system components due to voltage spikes and burning/pitting of plug contacts.
BTU (British Thermal Unit) - Unit of measure for heat. Defined as the amount of heat energy required
to heat one pound of water one degree Fahrenheit. One BTU would cause one pound of water at 40°F
to increase to 41°F. Used to quantify the capacity of refrigeration systems.
Capacity – Refrigeration system capacity is the BTUs per hour of heat energy that can be removed
from the cargo area. This must be more than the BTUs entering the truck body as heat.
Coil - Like a radiator, using airflow to cool the hot refrigerant. Refrigerant flows through tubing,
transferring heat into thin metal fins, which transfer heat into the air blowing through them.
Cold Plate – A rectangular steel shell filled with a eutectic solution. Internal refrigerant tubing passes
through the solution. Refrigerant freezes the solution. The cold plate absorbs heat from the
refrigerated compartment as the solution slowly thaws. Works like an ice pack.
Compressor – A sealed device, including the motor, with a vapor compression pump. Moves the
refrigerant through the system. Receives low-pressure vapor from the outlet of the cold plates,
sending it at high pressure to the condenser coil.
Condensing Unit – The assembly containing the compressor, condenser coil, electrical controls, and
other related devices of the refrigeration system. Either nose-mounted or skirt-mounted.
Defrost – Thawing frost from Cold Plates. Frost forms when humidity in the air passes over the cold
surface, freezing directly from water vapor into ice. Thick frost makes the Cold Plates not work well.
Eutectic – A mixture of substances which has a freezing/melting point lower than any of the
substances on their own. An example is water and salt. Cold Plates are filled with a eutectic solution
proprietary to their manufacturer.
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