WD Catalog 2018

819 / 1003

Air Conditioning /
Heating Function
• Cab Environment
• Heat Sources
• Heat Movement
• Heat Measurement
• Heat Relationships
• Changes of State
• Heat Movement During Changes of State
• Air Conditioner/Heater Functions
• Chapter Review
Cab Environment
The purpose of a heater/air conditioner system is to keep the driver comfort-
able. You are already familiar with your car system—if you are cold, you turn
on the heater. On a warm summer day, you either turn on the air conditioning
system or open the windows. Most people feel comfortable when they are
surrounded by air that is 70 to 80 degrees. Because truck drivers and heavy-
duty vehicle operators are usually in their cabs for long periods of time, the cab
temperature is very important to their comfort.
Truck and off-road cabs are hard to heat and cool. They have a large glass
area and are not always well insulated. Hot and cold weather directly affect the
temperature inside the cab. This means that any air conditioner/heater system
must have the capacity to do a lot of cooling or heating. Figure 1-1 shows the
temperature range inside a cab.
CAB
TEMPERATURE
RANGE
120°
32°
0°
70° 80°
1
Chapter
Figure 1-1
Inside cab environment
A 70 to 80 degree tempera-
ture range and modest
humidity level is best for
most people. The heater/AC
system should reach and
remain within this tempera-
ture range after a few min-
utes of operation.
1-1
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