GMC 1976 ZEO 6083 Maintenance Manual page 54

again . Then we can return the liquid refrigerant to
the evaporator to be used over again .
Actually, the vapor coming out of the evaporator
is very cold . We know the liquid refrigerant boils at
temperatures considerably below freezing and that
the vapors arising from it are only a shade warmer
even though they do contain quantities of heat .
Consequently, we can't expect to remove heat from
sub-freezing vapors by "cooling" them in air temper-
atures that usually range between 60°F . (15 .6°C .) and
100°F. (37 .8°C .) . . . heat refuses to flow from a cold
object toward a warmer object .
But with a pump, we can squeeze the heat-laden
vapor into a smaller space . And, when we compress
the vapor, we also concentrate the heat it contains .
In this way, we can make the vapor hotter without
adding any heat . Then we can cool it in compara-
tively warm air .
That is the only responsibility of a compressor in
an air conditioning system . It is not intended to be
a pump just for circulating the refrigerant . Rather,
its job is to exert pressure for two reasons . Pressure
makes the vapor hot enough to cool off in warm air .
At the same time, the compressor raises the re-
frigerant's pressure above the condensing point at
the temperature of the surrounding air so it will
condense .
SYSTEM COMPONENTS AND THEIR FUNCTIONS
The air conditioning system used on the GMC
Motor Home utilizes components in the following
catagories:
1 . The Refrigeration Components
2 . The Electrical Components
3 . The Vacuum Components
It is important that the operation of these compo-
nents be fully understood in order to properly diag-
nose and repair air conditioning problems.
REFRIGERATION COMPONENTS
The refrigeration components are those which
come in contact with and effect or are effected by the
Refrigerant-12 . They move it, cool it, warm it and
regulate it .
AIR CONDITIONING SYSTEM 1- 37
As the refrigerant leaves the compressor, it is still
a vapor although it is now quite hot and ready to give
up the heat that it absorbed in the evaporator. One
of the easiest ways to help refrigerant vapor dis-
charge its heat is to send it through a radiator-like
component known as a condenser .
The condenser really is a very simple device hav-
ing no moving parts . It does exactly the same job as
the familiar radiator in a typical home steam-heating
system. There,the steam is nothing more than water
vapor . In passing through the radiator, the steam
gives up its heat and condenses back into water .
The purpose of the condenser, as the name im-
plies, is to condense the high pressure, high tempera-
ture refrigerant vapor discharged by the compressor
into a high pressure liquid refrigerant . This occurs
when the high pressure, high temperature refrigerant
is subjected to the considerably cooler metal surfaces
of the condenser . This is due to the fundamental
laws, covered earlier, which state that "heat travels
from the warmer to the cooler surface," and that
"when heat is removed from vapor, liquid is pro-
duced ."
When the refrigerant condenses into a liquid, it
again is ready for boiling in the evaporator. So, we
run a pipe from the condenser back to the evapora-
tor .
COMPRESSOR
The prime purpose of the compressor (figure 10)
is to take the low pressure refrigerant vapor pro-
duced by the evaporator and compress it into a high
pressure, high temperature vapor which will be sent
on to the condenser .
It utilizes the principle that "when a vapor is
compressed, both its pressure and temperature are
raised" which we have already discussed . The com
pressor is mounted above the engine in a special
mounted bracket and is belt driven from the engine
through an electromagnetic clutch pulley on the
compressor.
The compressor has three double-acting pistons,
making it a six cylinder compressor. The compressor
has a 1 .5 inch bore and 1 .1875 inch stroke, giving it
a total displacement of 12 .6 cu . in . Identification of
the compressor is by model and serial number
stamped on a plate on top of the compressor.