The capillary tube for a 3/4 HP compressor depends on the refrigerant and the application temperature.
Key Points Before Selecting a Capillary Tube for a 3/4 HP Compressor
Capillary tubes rely on their length and diameter to determine total restriction:
- Impact of Diameter Changes: A percentage change in diameter affects the flow rate more significantly than an equivalent percentage change in length.
- Adjusting Restriction:
- Lengthening the tube increases restriction and slows the flow.
- Excessively long tubes become inefficient and often impractical.
- Shortening the tube gradually increases the flow until reaching a critical point where the flow rate accelerates with each reduction in length.
- Extremely short tubes may cause substantial increases in flow with minor length reductions. At this point, the tube behaves more like an orifice than a capillary tube.
General Recommendation: Keep the tube length between 5′ and 16′. While exceptions exist, adhering to this range minimizes operational issues.
Capillary Tube
Capillary Tube Table for 3/4 HP Compressor Using R134a:
| Application | Evaporation Temp. | Condensation Temp. |
|---|---|---|
| LBP (Low Pressure) | -23.3°C (-10°F) | 54.4°C (130°F) |
| MBP (Medium Pressure) | -6.7°C (20°F) | 54.4°C (130°F) |
| HBP (High Pressure) | 7.2°C (45°F) | 54.4°C (130°F) |
Source: Tecumseh
| Compressor Power (HP) | Application | Diameter (in) | Length (m) |
|---|---|---|---|
| 3/4 HP | HBP | 0.064 | 1.5 |
| 3/4 HP | MBP | 0.050 | 1.5 |
Source: Tecumseh
Capillary Tube Table for 3/4 HP Compressor Using R-410A
| Compressor Power (HP) | Evaporation Temp. | Diameter/Length |
|---|---|---|
| Low (-10°F) | 0.049 in / 104″ | |
| Medium (25°F) | 0.049 in / 44″ | |
| High (45°F) | 0.049 in / 34″ | |
| Alternate (requires two lengths): | 0.031 in / 50″ | |
| 0.042 in / 116″ | ||
| 0.042 in / 70″ |
Source: JB Industries
Capillary Tubes for 3/4 HP Compressor Using R404A
| Compressor Power (HP) | Application | Diameter (in) | Length (m) |
|---|---|---|---|
| 3/4 | LBP | 0.042 | 2.5 |
Source: Tecumseh
Capillary Tube Table for 3/4 HP Compressor Using R407C
| Compressor Power (HP) | Low Temp. | Medium Temp. | High Temp. |
|---|---|---|---|
| Diameter/Length | 0.049 in / 79″ | 0.049 in / 32″ | 0.064 in / 96″ |
| Two Capillaries of: | 0.031 in / 39″ | 0.042 in / 85″ | 0.042 in / 55″ |
