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GUIDES / AC COPPER PIPE
AC copper pipe size by tonnage.
Most wall-mounted split ACs use a 1/4″ liquid line with a 3/8″, 1/2″ or 5/8″ gas line, depending on capacity. Here are the sizes, wall thicknesses and length limits to check before you order, in inches and millimetres.
By Saurabh Jain, Refrigeration Centre · ·
What size copper pipe does a 1, 1.5 or 2 ton AC need?
Most wall-mounted inverter split ACs use a 1/4″ (6.35 mm) liquid line. The gas, or suction, line is typically 3/8″ (9.52 mm) at about 1 ton, 1/2″ (12.70 mm) at about 1.5 ton and 5/8″ (15.88 mm) at about 2 ton.
| AC capacity | Liquid line | Gas (suction) line |
|---|---|---|
| About 1 ton (3.5 kW) | 1/4″ (6.35 mm) | 3/8″ (9.52 mm) |
| About 1.5 ton (5 kW) | 1/4″ (6.35 mm) | 1/2″ (12.70 mm) |
| About 2 ton (7 kW) | 1/4″ (6.35 mm) | 5/8″ (15.88 mm) |
These are typical sizes, not rules. Some models use a larger gas line at the same capacity, and ducted, cassette and VRF units use bigger lines again. The connection sizes are printed in the outdoor unit’s installation manual and marked near its service valves, so take them from there. Manuals often round the sizes to 6.4, 9.5, 12.7 and 15.9 mm; those are the same 1/4″, 3/8″, 1/2″ and 5/8″ tubes.
What wall thickness do R32 and R410A need?
R32 and R410A run at much higher pressure than R22, so their installation manuals set a minimum wall thickness for each pipe size. A common set of minimums, from Fujitsu General’s R32 and R410A installation information, is:
| Pipe size | Minimum wall | Nearest SWG |
|---|---|---|
| 1/4″ (6.35 mm) | 0.80 mm | 21 SWG (0.81 mm) |
| 3/8″ (9.52 mm) | 0.80 mm | 21 SWG (0.81 mm) |
| 1/2″ (12.70 mm) | 0.80 mm | 21 SWG (0.81 mm) |
| 5/8″ (15.88 mm) | 1.00 mm | 19 SWG (1.02 mm) |
| 3/4″ (19.05 mm) and up | Half-hard (1/2H) tube, or as the manual allows | Per the manual |
Pipe sold as “22 gauge” is 22 SWG, which is 0.71 mm and below the 0.8 mm minimum. Quote the wall in millimetres when you order. The gauge chart converts every SWG size.
What are the liquid line and the suction line?
The liquid line is the smaller pipe. It carries refrigerant from the condenser side to the indoor coil, as liquid or, in most splits where expansion happens at the outdoor unit, as a cold mix of liquid and vapour. The suction, or gas, line is the larger pipe; it returns low-pressure vapour from the indoor coil to the compressor. Both lines run cold in cooling mode, so insulate each one separately.
How long can the pipe run be?
The installation manual gives three figures: the maximum pipe length, the maximum height difference between the indoor and outdoor units, and the pre-charged length. Up to the pre-charged length, the factory charge is enough. Beyond it, add refrigerant at the rate per metre the manual states. Extra length and bends cost cooling capacity, so keep the run short and direct.
How much pipe should I order?
Measure the route the pipes will actually take, not the straight-line distance between the units. Add the bends and a small allowance for flaring and a service loop. Then order:
- the liquid line and the gas line, each for the full route, in the sizes and wall thickness the manual gives;
- nitrile insulation tube for each line, with the inner diameter (ID) matched to the pipe’s outside diameter;
- wrapping tape for the outdoor run and drain pipe for the indoor unit;
- R410A/R32-pattern flare nuts, if the unit’s own nuts are missing.
Refrigeration Centre sells full 50 ft (15.24 m) coils and 10 ft (3.05 m) straight lengths, and cuts either to the run you measured, down to 1 ft. Sizes 1/4″ to 7/8″ come as soft coil or straight lengths.
What about VRF, ducted and cold-room systems?
VRF and VRV systems take their pipe diameters from the manufacturer’s piping-design rules or software: soft coil for small branch lines and hard-drawn straight lengths for mains and risers, often larger and with heavier walls than split-AC piping. Joints are brazed under a nitrogen purge, and branches use the manufacturer’s own refnet or branch kits.
Cold rooms and commercial refrigeration use the same ACR tube, sized from the compressor or condensing-unit maker’s tables. Low-temperature suction lines need thicker insulation, and suction risers must be sized so that oil returns to the compressor.
Refrigeration Centre holds hard-drawn copper in the common sizes up to 2-1/8″, with matching copper fittings; larger sizes can be sourced on order. We also supply Copeland scroll compressors for refrigeration and air conditioning.
Can I reuse the old R22 pipes?
Only if the new unit’s manual allows it and the piping passes three checks: the wall meets the R32/R410A minimum thickness, the lines are flushed of old mineral oil and debris, and every flare is re-made with R410A/R32-pattern flare nuts. At 1/2″ and 5/8″ those nuts are larger: 26 mm and 29 mm across flats, against 24 mm and 27 mm for R22. If any check is in doubt, run new pipe.
Installing the pipe.
Use a bender for tight bends so the tube does not kink or flatten. Joints are brazed under a flow of dry nitrogen, and the system is pressure-tested and evacuated before the service valves are opened. The brazing guide covers brazing, why nitrogen matters and pressure testing and evacuation.
Sources: wall-thickness minimums from Fujitsu General installation information for R32/R410A units; pipe sizes from published split-AC manufacturer specifications.
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