3.คำนวณ นม. ที่ต้องใช้
6.8 Oil Charge
?Oil Circulation Ratio (OCR) should be between 3.3% and 8% ratio of oil to refrigerant
by weight.
นน. นม. ต่อ refrigerant ระหว่าง 3.3-8% ใช้สัก 6%
สมมุติcase 6.8.2.1 นน.R134aได้ 1000กรัม นน. นม.=1000g*0.06=60กรัม=2.11644ounces นำค่านี้ไปหัก ออกจากข้อ2ข้างบนเพื่อเติมเพิ่มเท่านี้
6.8.1 Oil Flow Theory
?Compressor lubrication occurs as the oil which circulates with the refrigerant passes
through the compressor crankcase during operation. The Sanden SD series
compressor achieves optimal durability and cooling performance when oil circulates
through the system at a ratio of 3.3% to 8% oil to refrigerant. Excess oil can act as an
insulator limiting heat transfer in the evaporator and condenser, while too little oil can
negatively affect durability.
?Oil will collect in low pressure cool components (evaporator, accumulator and suction
hose) of the refrigerant loop. For example a long suction hose which sags can collect
several ounces thus reducing overall oil circulation ratio.
6.8.2 Oil Charging
6.8.2.1 Passenger Car, Light Duty Truck Single Evaporator
Refrigerant charges 24oz (680g) to 40oz (1133g)
?135cc oil TXV systems
?240 cc oil in orifice tube systems
6.8.2.2 Dual Evaporator Long Hose Systems
Less than 56oz or 1600g of refrigerant charge
1. The desired oil charge for the systems with unusually long hoses, such as trucks, tractors,
etc., can be determined based on the total refrigerant charge when less than 56 oz. (1600g)
refrigerant is used.
2. Calculate the desired oil charge as below:
Oil amount (oz.) = [(Refrigerant charge in oz. x 0.06) + 2.2] ? 0.9.
Oil amount (cc) = [(Refrigerant charge in grams x 0.06) + 66] ? 0.9.
Note: For systems with very long hose runs add an additional 1.0 oz (30cc) of oil for
each 10 foot of hose plus an additional 1.1 oz (33cc) as a safety measure.
Long Hose Example:
A system w/ a 32oz refrigerant charge and 11ft long suction hose:
Refrigerant Charge
Suction Hose Length
Oil charge = [[[(32oz x 0.06)+2.2] ? 0.9] + (1oz/10ft x 11ft)] x 1.1 safety factor
= 4.6 oz + 2.2 oz for total of 6.8 oz
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