Electrical Systems - Chassis
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Evaporator - A tube core and fins are used in the evaporator similar to
the condenser. Air is blown through the fins to allow the evaporator to cool and
reduce the pressure.
Blower and Motor - Just as the condenser has a fan, the evaporator has a
fan called the blower. The blower will draw air from the cab area and force the
air over the evaporator coils and fins. This forced air will ensure continuous
vaporizing of the R134a.
Relays and Switches - Both electronic and vacuum switches are used in
the control and operations of the system.
Chemical Stability:
The air conditioning system life and efficient operations depends upon the
chemical stability of the refrigeration system. The refrigeration system is made
of Refrigerant-R134a and Polyakylene Gycol (PAG) synthetic lubricant. It is
very important that all materials contained within the refrigerant system be
chemically compatible. The only suitable compound for use with R134a is PAG.
The total amount of PAG within the refrigerant system is approximately 18% of
the total refrigerant in the system.
How much refrigerant is in the system or how much should be used when
charging? You will need 1 oz. of PAG for each 7 feet of hose after the first 15
feet of hose. Roughly, a 40 foot motorhome will use 92 feet of refrigerant hose.
Take 15 feet off the measurement and the result would be 77 feet. This 77 feet
is then divided by 7 for total of 11. This
represents the number of ounces of PAG
oil needed for the A/C system, 11 oz.
Carrying the formula one step fur-
ther, the 11 oz. equal approximately 18%
of the entire system. The total will equate
to approximately 61 oz. or 3.8 lbs. of R-
134a.
High pressure readings are another
way to determine the amount of charge.
The ambient temperature reading is meas-
ured one inch away from the condenser.
The ambient temperature reading, plus
40°F, will equate to a value from the pres-
sure table.
EXAMPLE: 90° F
1 inch from condenser
+40°F
130°F ----- 198.90
TEMP F/ PSIG
16 15.69
18 17.04
20 18.43
22 19.73
24 21.35
26 22.88
28 24.47
30 26.10
32 27.79
34 29.52
36 31.32
38 33.17
40 35.07
42 37.03
44 39.05
45 40.09
50 45.48
55 51.27
TEMP F/ PSIG
60 57.47
65 64.10
70 71.19
75 78.75
80 86.80
85 95.40
90 104.40
91 106.30
92 108.20
93 110.20
94 112.10
95 114.10
100 124.30
102 128.50
104 132.90
106 137.30
108 141.90
110 146.50
TEMP F/ PSIG
112 151.30
114 156.10
116 161.10
118 166.10
120 171.30
122 176.60
124 182.00
126 187.50
128 193.10
130 198.90
135 213.70
140 229.40
145 245.80
150 263.00
155 281.00
160 300.10
165 320.00
170 340.80
WINDSOR
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