WD Catalog 2018

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Chapter 1 – Air Conditioning / Heating Function
1-4 G - -
HEATER
GIVES UP
HEAT ENERGY
TO AIR IN CAB
CONDENSER
GIVES UP HEAT
ENERGY TO
OUTSIDE ENERGY
H
H
H
HH
Heat Measurement
There are two ways to measure heat—heat intensity in degrees Fahrenheit, or
degrees Celsius, and heat quantity in British thermal units (BTU’s).
Heat Intensity
We measure heat intensity (how hot something is) as temperature in
degrees Fahrenheit (or in the metric form, degrees Celsius). In your
service work on HVAC systems, you may use a dial type thermometer to
measure heat intensity. Figure 1-6 illustrates a typical dial type ther-
mometer. It’s an ideal tool for measuring heat intensity as you work to
check out or troubleshoot these HVAC systems. The chart in Figure 1-7
converts degrees Fahrenheit to degrees Celsius.
DEGREES
FAHRENHEIT
80
0
160
20
40 60
100
120
140
-20
180
-40
NEEDLE MEASURES HEAT ENERGY
TEMPERATURE SENSING PROBE
Figure 1-5
Note the heater core and air
conditioner condenser in
this illustration. Both serve
these systems as the main
point of heat energy radia-
tion. The heater radiates
heat to warm the vehicle
occupants. The condenser
radiates heat from the
refrigerant to the air out-
side the cab.
Figure 1-6
A typical dial type ther-
mometer has a probe on it
that extends about six
inches. The probe senses
and indicates the tempera-
ture in hard to reach
places—such as in air distri-
bution ducts.