Refrigerant line charge calculator
Split systems ship with enough refrigerant for a standard line length. Anything beyond that needs topping up by the pipe volume.
g per metre
Extra refrigerant to add
150g
- Total system charge
- 1250
- Line beyond the included length
- 7.50
- Liquid line bore
- 4.75
- Line volume per metre
- 0.018
- Total line volume
- 0.3
- Increase over the factory charge
- 13.6 %
Show the working
- Liquid line length = 15
- Length covered by the factory charge = 7.5
- Liquid line outside diameter = 6.35
- Wall thickness = 0.8
- Charge rate = 20
- Factory charge = 1100
- Line beyond the included length = max(15 - 7.5, 0) = 7.5
- Extra refrigerant to add = 7.5 * 20 = 150
- Total system charge = 1100 + 150 = 1250
- Liquid line bore = 6.35 - 2*0.8 = 4.75
- Line volume per metre = pi * (4.75/2)^2 / 1000 = 0.017 720 5
- Total line volume = 0.017 720 5 * 15 = 0.265 808
- Increase over the factory charge = 1100 > 0 ? 150/1100*100 : 0 = 13.6364
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- extra charge = (line length - included length) x charge rate per metre
Charge rates are specific to the equipment and the line size; always use the figure on the unit data plate.
Handling refrigerant requires certification in most jurisdictions, and venting it is illegal.