WD Catalog 2018

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Glossary
i-4 - -
heat intensity — the temperature of a substance
or material as measured by a thermometer
heat load — the amount of heat contained in a
given situation
heat quantity — the amount of heat measured in
BTU’s (British Thermal Units)
heater — an apparatus that provides heat
heater core — an assembly of metal tubing and
fins used to exchange heat from engine coolant to
cab air
Hg — the symbol used for mercury in the Periodic
Table of Elements
HVAC — heating, ventilation, and air conditioning
high load condition — the circumstance when
the air conditioning system is operating at maxi-
mum capacity to cool a given environment
high pressure cutout switch — a switch which
cuts out the compressor clutch if pressure in the
system rises above a pre-set level
high pressure lines — the lines that carry high
pressure refrigerant gas and liquid between the
compressor, condenser, receiver-drier and expan-
sion valve
high side — the high pressure side of a system
(gas or liquid) from the compressor outlet to the
expansion valve orifice
high side low pressure cutout switch — a
switch (on the high pressure line) which cuts out
the compressor clutch if pressure in the system
drops below a pre-set level
high side service valve — a valve on the com-
pressor used to service the high pressure side of the
system and permit it to be checked
humidity — the degree of moisture or wetness in
the air (atmosphere)
hydrochloric acid — a corrosive chemical created
within an air conditioning system when moisture
and R-12 combine under pressure
ideal comfort range — a temperature range, gen-
erally between 70 and 80 degrees Fahrenheit,
where most people are comfortable
in. Hg (inches of mercury) — a unit used to
measure vacuum
inch-pound — a measurement of energy required
to raise one pound one inch. In relationship to
torque, it is the force that acts upon a body (bolt or
nut) to produce rotation
in-line compressor — a 2-cylinder compressor
whose pistons are side-by-side, i.e.. Tecumseh, York
in-line drier — a drier located after the receiver-
drier but before the expansion valve; absorbs and
moisture escaping from the receiver-drier
in-line muffler — a device to reduce noise from
the high side of the compressor
intercooler — an air-to-air heat exchanger used
on some heavy duty vehicles, that mounts in front
of the radiator to cool the intake air on a turbo-
charged engine. Also called a charge-air cooler
KLEA — Technical Chemical Company trademark
for R-134a
latent heat of evaporation — the amount of heat
required by a substance to change it’s state from a
liquid to a gas without raising it’s temperature
leak detector — a device which detects any refrig-
erant leaks in an air conditioning system
Legris air fitting — a patented push-on connector
(fitting) used in AC/heater air control systems to
attach tubing and designed for a positive leak free
seal and quick disconnect
liquid line — the line from the outlet of the re-
ceiver-drier to the expansion valve inlet
low head pressure — a system malfunction
which causes the high side pressure to be lower
than required for proper system operation
low side low pressure cutout switch — a switch
(on the suction line) which cuts out the compressor
clutch if pressure in the system drops below a pre-
set level