A system holds a factory charge plus extra refrigerant for line sets longer than a baseline. Adjusted charge = factory charge + (extra feet × per-foot adder).
The example
6 lb factory, 40 ft line, 15 ft base.
| A | B | |
|---|---|---|
| 1 | Item | Value |
| 2 | 25 extra ft × 0.6 oz | 15 oz |
| 3 | Total | → ~6.94 lb |
The formula
The formula:
How it works
How it works:
- Start with the factory charge (in ounces; 1 lb = 16 oz).
- Add (line length − baseline) × per-foot adder — MAX floors it at zero.
- The per-foot adder comes from the equipment data plate (e.g. 0.6 oz/ft).
- Always weigh in the charge and verify by superheat/subcooling — never guess.
Weigh the charge, then verify — the formula is a starting point. The line-length adder gives the target charge to weigh in, but final charge is confirmed by superheat (fixed orifice) or subcooling (TXV) against the manufacturer’s spec. Overcharging and undercharging both wreck efficiency and shorten compressor life. Recover and weigh; don’t top off by gauge pressure alone. This is illustrative, not an EPA/handling procedure.
Try it: interactive demo
Factory charge (lb), line length, baseline, oz/ft.
Variations
Added ounces
Extra length:
Total in pounds
Convert oz:
Per-foot from data plate
If charge per total:
Pitfalls & errors
Floor at zero. Short line sets add nothing — MAX.
oz vs lb. Keep units straight (16 oz = 1 lb).
Verify by SH/SC. Weigh in, then confirm by superheat/subcooling.
Practice workbook
Frequently asked questions
How do I calculate refrigerant charge for a line set in Excel?
What's the per-foot adder?
Is the calculated charge final?
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