Refrigerant Line Sizing Calculator

Lineset size, extra charge per foot, and a sizing chart. Also in the Blueprint iOS app.

Project Details
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Results
Calculated estimates for your project
Liquid line3/8 in OD
Suction (vapor) line3/4 in OD, alternate 7/8 in
Equivalent length33 ft (25 ft + 4 bends)
Extra refrigerant6.0 oz
How we got this(25 ft - 15 ft precharge) x 0.60 oz/ft for a 3/8 in liquid line
Capacity lossabout 0.5%
LengthOK
LiftOK

Turn these numbers into a build plan.

  • 3/8 in liquid
  • 3/4 in suction
  • 6.0 oz extra charge
R-410A sizing table, your row highlighted
TonsLiquidSuction, to 50 ftSuction, long line
1.51/4 in5/8 in3/4 in
23/8 in3/4 in3/4 in
2.53/8 in3/4 in7/8 in
33/8 in3/4 in7/8 in
3.53/8 in7/8 in7/8 in
43/8 in7/8 in1 1/8 in
53/8 in1 1/8 in1 1/8 in

Save this lineset spec and install checklist below: the parts list, the steps through the vacuum, and the charge step marked for a pro with EPA 608 certification.

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Project plan · built from your numbers

Run a 3/8 x 3/4 in R-410A line set, 25 ft

A 2.5 ton split system with 25 ft of line (33 ft equivalent) takes a 3/8 in liquid and 3/4 in suction line and about 6.0 oz of extra R-410A.

Materials
$490
Time
1 to 2 days, plus a pro visit to charge
Level
Advanced
5 steps 5 tools 4 materials
  1. 1

    Mount the units

    Set the outdoor unit level on a pad or brackets and mount the indoor unit or air handler, keeping the run as short and straight as you can.

  2. 2

    Run the line set

    Route 25 ft of 3/8 x 3/4 in line with no more than 4 sharp bends, insulation intact, and the drain line sloped down.

  3. 3

    Make the connections

    Cut square, deburr, flare or braze per the unit manual (braze under nitrogen flow), and torque flare nuts to spec.

01 · Your numbers
Liquid
3/8 in
Suction
3/4 in
Extra charge
6.0 oz
Est. cost
$490
02 · The plan

5 steps · 5 tools · 4 materials

2 more steps, the full tool list and a shopping list you can check off as you go.

03 · Finished

Your plan is 60% built. Save it.

3/5

Run a 3/8 x 3/4 in R-410A line set, 25 ft

Finished in 1 to 2 days, plus a pro visit to charge · $490 DIY

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Refrigerant line size chart

R-410A, R-454B and R-32 split systems: liquid x suction OD in inches by equivalent length
Tons25 ft50 ft75 ft100 ft150 ft
1.51/4 x 5/81/4 x 5/81/4 x 3/45/16 x 3/45/16 x 3/4
23/8 x 3/43/8 x 3/43/8 x 3/43/8 x 3/43/8 x 3/4
2.53/8 x 3/43/8 x 3/43/8 x 7/83/8 x 7/83/8 x 7/8
33/8 x 3/43/8 x 3/43/8 x 7/83/8 x 7/83/8 x 7/8
3.53/8 x 7/83/8 x 7/83/8 x 7/83/8 x 7/83/8 x 7/8
43/8 x 7/83/8 x 7/83/8 x 1 1/83/8 x 1 1/83/8 x 1 1/8
53/8 x 1 1/83/8 x 1 1/83/8 x 1 1/83/8 x 1 1/83/8 x 1 1/8
R-22 (legacy) split systems
Tons25 ft50 ft75 ft
1.51/4 x 3/41/4 x 3/41/4 x 3/4
23/8 x 3/43/8 x 3/43/8 x 7/8
2.53/8 x 7/83/8 x 7/83/8 x 7/8
33/8 x 7/83/8 x 7/83/8 x 1 1/8
3.53/8 x 1 1/83/8 x 1 1/83/8 x 1 1/8
43/8 x 1 1/83/8 x 1 1/83/8 x 1 1/8
51/2 x 1 1/81/2 x 1 1/81/2 x 1 3/8

Lines over 150 ft are outside most residential limits. The outdoor unit's installation manual always wins over a general chart.

How much refrigerant per foot of line set

Extra charge per foot of liquid line, past the factory precharge length
Liquid line ODR-410AR-454BR-32R-22 (legacy)
1/4 in0.25 oz0.24 oz0.23 oz0.28 oz
5/16 in0.40 oz0.39 oz0.36 oz0.45 oz
3/8 in0.60 oz0.58 oz0.54 oz0.67 oz
1/2 in1.20 oz1.16 oz1.08 oz1.34 oz

Extra charge = (line length - precharge length) x oz per foot. Most split systems are precharged for 15 ft and mini-splits for 25 ft (check the nameplate). Suction vapor weighs so little it is ignored.

Worked example: 3 ton, 45 ft, 4 bends

  1. Start from the tonnage. A 3 ton R-410A split system lists a 3/8 in liquid line and a 3/4 in suction line for runs up to about 50 ft.
  2. Add the fittings. 45 ft of line plus four 90 degree bends at about 2 ft each is 53 ft equivalent.
  3. Check the long-line rule. Over 50 ft equivalent, step the suction line up to 7/8 in to hold capacity. The outdoor unit is below, so there is no suction riser and oil return is not a problem.
  4. Work out the extra charge. The unit is precharged for 15 ft. (45 - 15) x 0.6 oz/ft for a 3/8 in liquid line = 1.13 lb (18.0 oz) of extra R-410A.
  5. Check the limits. About 1.7% capacity loss, 10 ft of lift with the indoor unit above: within typical limits.

Result: 3/8 in liquid, 7/8 in suction (3/4 in acceptable), 1.13 lb (18.0 oz) extra charge.

Suction line sizing: velocity and oil return

The suction line carries cold vapor and the compressor oil back to the outdoor unit. Too small and the pressure drop costs capacity; too big and the vapor moves too slowly to carry oil up a vertical riser. That is why long horizontal runs step up a size, but a riser (outdoor unit above the indoor unit) stays at the standard size and gets an oil trap at the bottom and every 20 ft or so of lift.

Mini-split line sizes

Indoor unitLiquidSuction
12,000 BTU1/4 in3/8 in
18,000 BTU1/4 in1/2 in
24,000 BTU1/4 in5/8 in
36,000 BTU3/8 in5/8 in

What you can do yourself, and what needs EPA 608

Mounting units, running and insulating the line set, flaring, the nitrogen pressure test and pulling a vacuum are within a careful DIYer's reach, and pre-charged DIY mini-splits are sold for that. Opening a system, recovering old refrigerant and adding charge require EPA Section 608 certification. R-32 and R-454B are A2L (mildly flammable) refrigerants: follow the unit manual for brazing, leak detection and charging. The next steps for the install are the condenser circuit in the electrical load calculator, duct runs in the ductwork sizing calculator, filters in the MERV filter guide and payback in the energy savings calculator.

Refrigerant line sizing FAQ

What size line set for a 2 ton unit?

For R-410A, R-454B or R-32: 3/8 x 3/4 in (liquid x suction). R-22: 3/8 x 3/4.

What size line set for a 3 ton unit?

3/8 x 3/4 in up to about 50 ft, and 3/8 x 7/8 on longer runs.

What size line set for a 4 or 5 ton unit?

4 ton: 3/8 x 7/8 in. 5 ton: 3/8 x 1 1/8 in. Above 5 tons, use the manufacturer's sizing tool.

How much refrigerant per foot of line set?

For R-410A, about 0.6 oz per foot of 3/8 in liquid line and 0.25 oz for 1/4 in, past the length the unit is precharged for (usually 15 ft, 25 ft on mini-splits). Suction line vapor adds almost nothing.

Can I reuse an R-22 line set with R-410A or R-454B?

Often, if it is the right size, holds a nitrogen pressure test and is flushed of mineral oil. Many R-22 suction lines are one size larger than an R-410A system wants, which can hurt oil return on a riser. Check the new unit's manual.

What is the maximum line set length?

Most residential split systems allow 50 to 80 ft as standard and up to about 150 ft with the long-line guide (crankcase heater, charge and capacity adjustments). Mini-splits list their own maximum on the spec sheet, often 50 to 100 ft.

Does a mini-split need a different size?

Use the flare port sizes on the unit: typically 1/4 x 3/8 in for 9,000 to 12,000 BTU, 1/4 x 1/2 for 18,000 and 1/4 x 5/8 or 3/8 x 5/8 for 24,000 to 36,000.

What are line set sizes in metric?

Copper line sets are sold in inch ODs worldwide: 1/4 in = 6.35 mm, 3/8 = 9.52 mm, 1/2 = 12.7 mm, 5/8 = 15.88 mm, 3/4 = 19.05 mm, 7/8 = 22.22 mm. Charge in grams: 0.6 oz/ft is about 56 g/m.

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