The type of POE oil used for R134a depends on the type of compressor in the system, the manufacturer, and other considerations.
R134a is most commonly used in domestic and commercial refrigeration equipment with low capacity, medium-to-high-capacity water chillers, and automotive air conditioning systems.
In general, manufacturers of domestic and low-power commercial systems typically use low-viscosity POE oils, but it is always recommended to consult the manufacturer’s specifications.
Applications in Domestic and Medium-Capacity Commercial Systems
| Application Type | Oil Type |
|---|---|
| Very low-capacity compressors | POE 22 |
| Low- and medium-capacity compressors | POE 32, POE 22, POE 10 |
(Data extracted from compressor manufacturers)
POE Oil for R134a Refrigerant
The oil required for R134a in the domestic and commercial sectors is POE oil.
Polyolester (POE) oil is highly hygroscopic, meaning it absorbs moisture from the environment quickly. This absorbed moisture can degrade the oil.
For example, leaving a container of POE oil open for more than 12 minutes will result in significant absorption of atmospheric moisture. To prevent this, always keep oil containers tightly sealed when not in use or utilize an oil pump.
Common Compressors Used
The majority of low- and medium-capacity refrigeration systems utilize piston compressors.
While the lubricant’s characteristics depend on the compressor manufacturer, technicians often face situations where the equipment’s technical specifications are unavailable. In such cases, the replacement oil should have similar technical characteristics to the original and come from a reputable brand to ensure reliable operation.
Challenges in Split Air Conditioning Systems
Oil return can be a significant challenge in split air conditioning systems. The oil must travel from the evaporator in the indoor unit to the compressor in the outdoor unit.
Issues such as improper pipe inclination or placement can hinder the proper return of lubricating oil. However, the type of lubricant used is critical for the system’s proper functioning.
When oil fails to return adequately to the compressor, insufficient lubrication may occur, leading to premature compressor wear and a shorter lifespan. Additionally, excessive oil in the evaporator can reduce the system’s efficiency and performance.
Benefits of POE Oil for R134a
POE oil is an excellent choice for piston compressors using R134a due to its quality and viscosity. However, it is crucial to ensure the oil used has a viscosity stability index close to or greater than 100.
The viscosity stability index is a numerical measure of how an oil’s viscosity changes with temperature fluctuations. Oils with a viscosity index of 100 or higher are considered very stable across a wide temperature range. A lower index indicates that the oil’s viscosity is more affected by temperature changes.
Approximate Oil Quantities for Piston Compressors
| Compressor Power | Approximate Oil Quantity |
|---|---|
| 1/12 HP | 160 cm³ |
| 1/10 HP | 160 cm³ |
| 1/8 HP | 180 cm³ |
| 1/6 HP | 220 cm³ |
| 1/5 HP | 230 cm³ |
| 1/4 HP | 230 cm³ |
| 1/3 HP | 380 cm³ |
| 1/2 HP | 480 cm³ |
| 3/4 HP | 600 cm³ |
| 1 HP | 750 cm³ |
| 1 1/4 HP | 1000 cm³ |
| 1 1/2 HP | 1140 cm³ |
Using high-quality POE oil with a stable viscosity index is essential to ensure optimal performance and durability in systems utilizing R134a refrigerant.
