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Glossary
190
HFC:
A refrigerant consisting of hydrogen, fluorine and
carbon. Examples: R134a and 404A. HFC refrigerants contain
no chlorine and are, therefore, considered “safe” for the
environment.
high pressure relief valve:
A safety valve on the
refrigeration system that allows refrigerant to escape from the
system if pressure exceeds a predetermined value.
hp (horsepower):
A unit of power equivalent to 746 watts
or 550 foot-pounds per second.
HPCO (High Pressure Cut Out Switch):
A
pressure-operated switch that opens to stop unit operation
when discharge pressure reaches a predetermined maximum.
invertible:
A multi-temperature truck or trailer unit designed
to allow the placement of deep-frozen cargo in any
compartment. See Multi-Temp.
kPa:
Kilopascals. A metric unit of pressure. 1 kPa = 0.01 bar =
0.145 psi.
load:
1) The product being refrigerated and transported.
2) The amount of heat being removed by the refrigeration
system. (For example, a compressor is under a heavy heat load
when expected to cool a very warm box.)
LPCO (Low Pressure Cut Out Switch):
A
pressure-operated switch that opens to stop unit operation
when suction pressure reaches a predetermined minimum.
modulation:
An optional system that reduces load (product)
dehydration and avoids “top freeze.”
movable bulkhead:
A thick, insulated, portable wall-like
device used to compartmentalize a temperature-controlled
truck or trailer. See bulkhead.
Multi-Temp:
A Thermo King truck or trailer unit capable of
maintaining different set-points in multiple compartments.
no. 1 diesel fuel:
A grade of diesel fuel formulated to
prevent “jelling” in low ambient temperatures.
no. 2 diesel fuel:
A grade of diesel fuel formulated for
moderate to warm ambient temperatures.
ohm:
An electrical unit measuring the amount of resistance
(opposition to the current flow) in an electrical circuit.
pre-cooling:
1) To cool down an empty box
(temperature-controlled area) to the desired load temperature
prior to loading. 2) To cool cargo to a desired temperature
before loading.