1/6–1/4 HP Copper Capillary Tube Ø0.90 × Ø1.90 mm – Capillary Tube, 15 kg and Multiples

Copper capillary tube is a fixed-bore copper tube with an inside diameter of Ø0.90 mm and an outside diameter of Ø1.90 mm. In small and medium-capacity refrigeration circuits it acts as the expansion device: it throttles the high-pressure liquid refrigerant coming from the condenser down to evaporator pressure.

Capillary Tube: The Fixed-Bore Expansion Device of Small Refrigeration Circuits

Unlike a thermostatic expansion valve (TXV), it has no moving parts; the throttling effect is determined entirely by the inside diameter and length of the tube. As a result it does not fail, needs no adjustment and is very low in cost. On the other hand, its capacity is fixed — it cannot adjust itself when the load changes, so it is used in systems with a largely constant load.

This size is typically chosen for refrigerators and small freezers. When the compressor stops, the capillary tube allows the circuit pressures to equalize; therefore it can be used with RSIR-start (low starting torque) compressors.

Technical Specifications

• Inside Diameter: Ø0.90 mm | Outside Diameter: Ø1.90 mm | Wall Thickness: 0.500 mm
• Material: Electrolytic copper (Cu-DHP), refrigeration grade
• Applications: Refrigerators, freezers, display cabinets, bottle coolers, water dispensers and small commercial refrigeration circuits
• Compatibility: R134a, R600a, R290, R404A and other common refrigerants
• Sales Unit: 15 kg and multiples (coil) — price is per kilogram
• Delivery Form: In coils, clean and capped

• 🔧 Length calculation is critical: Even with the same inside diameter, if the tube is too short there is overfeeding (the evaporator floods, liquid reaches the compressor); if it is too long there is underfeeding (capacity drops, excessive superheat). The length is determined by the compressor capacity, the refrigerant type and the operating range.
• ✂️ Cutting method: Do not cut the capillary tube with a saw or side cutters — the burr narrows the bore and blocks the tube. Use a capillary tube cutter, or score it and snap it; check the bore after cutting.
• 🧊 A filter drier is essential: A filter drier must always be fitted at the inlet of the capillary tube. The most common cause of failure is blockage by moisture and dirt; because the bore is so small, even the smallest particle stops the flow.
• 🌡️ Heat exchange with the suction line: If part of the capillary tube is placed in contact with and soldered to the suction tube (heat exchanger effect), efficiency increases and liquid return to the compressor decreases.
• Do not let solder run inside when brazing and purge with nitrogen; oxide residue blocks the capillary tube.

What does the "1/6–1/4 HP" at the start mean?

In the trade, capillary tubes are referred to by the horsepower (HP) of the compressor they match. "1/6–1/4 HP capillary" means that this bore is typically used in a circuit running with a 1/6–1/4 horsepower compressor — it is not the power of the tube itself.

The logic is simple: as the compressor gets bigger, the amount of refrigerant that must circulate in the circuit increases, so a capillary tube with a larger bore is needed. Common equivalents:

• Ø0.80 mm → 1/6 HP  ·  Ø1.00 mm → 1/4 HP  ·  Ø1.20 mm → 1/3 HP  ·  Ø1.30 mm → 1/2 HP
• Ø1.50 mm → 3/4 HP  ·  Ø1.80 mm → 1 HP  ·  Ø2.00 mm → 1.5 HP

⚠️ This is a starting point, not a strict rule. The behavior of a capillary tube is determined as much by its length as by its bore; in addition, the refrigerant type (R134a, R600a, R290…) and the operating range (freezer / cooler) change the result. Even two systems of the same horsepower may need different lengths. For an exact selection, refer to the system manufacturer's table or a circuit calculation; if you are fitting the same tube as the one removed, measure its length exactly as well.