Electrical Systems - Chassis
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DIPLOMAT
9•254
How much refrigerant is in the system. 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 further, the 11 oz. equal approximately
18% of the entire system. The total will equate to approximately 61 oz. or 3.8
lbs. of R134a.
High pressure readings are another way to determine the amount of
charge. The ambient temperature reading is measured one inch away from the
condenser. The ambient temperature reading, plus 40°F, will equate to a value
from the pressure table.
EXAMPLE: 90° F
1 inch from condenser
+40°F
130°F ----- 198.90
PSIG-On fully charged system the expected pressure that should be seen
on the HIGH-SIDE gauge will be around 200 PSIG.
NOTE: All systems are charged at the factory with 4.0 lbs of
R134A.
R-134a Refrigerant:
R134a is classified non-explosive, non-flammable and non-corrosive.
There is hardly any odor and it is much heavier than air. R134a is ozone friend-
ly; however, it is not technician friendly. Proper care in handling and adequate
ventilation must be observed. Under normal atmospheric pressures and tempera-
tures R134a will evaporate so quickly it will freeze anything it comes in contact
with. The open container boiling point for R134a is minus 21.7º F. This low
boiling point makes for an ideal refrigerant. The tremendous amount heat trans-
fer which occurs when a liquid boils, or vapors condense, forms the basic prin-
ciples of all A/C systems. The amount of heat required to raise or lower the
temperature of one pound of water by 1º F equals one British Thermal Unit
(BTU). The BTU is the standard measurement of an air conditioner system.
Safety and Handling of 134A and Pag Oil:
• When working with any refrigerant system wear eye protection and hand
protection.
• Pag Oil irritates the skin. Flush with water immediately if in
contact with any body part.
• Ensure any service work performed on the A/C system is in a well
ventilated work area.
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