Checks a system's refrigerant charge against the BS EN 378 practical limit for the room it's installed in, max charge = practical limit (kg/m³) × room volume.
General occupancy (EN 378 Category A) only, tender-stage check, verify to a full EN 378 assessment where required.
For design guidance only. Always verify with a qualified engineer against a full EN 378 safety-classification assessment.
About this refrigerant charge limit calculator
This free refrigerant charge limit calculator checks whether a refrigeration or air-conditioning system’s charge is safe for the room it serves, comparing the charge against the BS EN 378 practical limit for that refrigerant. It is aimed at refrigeration and air-conditioning engineers, designers and installers sizing R32, R410A, R134a, R290, R744 or R717 systems, and returns the maximum charge the room can hold, the minimum room volume the charge needs, and the concentration if the whole charge leaked out. It covers general occupancy (EN 378 Category A) only. Everything runs in your browser. Nothing is uploaded.
How the charge limit is calculated
Per BS EN 378-1 Annex E, the room volume is floor area × ceiling height and the maximum charge = practical limit (kg/m³) × room volume. The practical limit is read from the standard’s own per-refrigerant table, for example 0.061 kg/m³ for R32, 0.44 kg/m³ for R410A, 0.008 kg/m³ for R290 and 0.00035 kg/m³ for R717, and the governing hazard is flammability or toxicity by safety class. The tool also inverts the relation to the minimum room volume = charge ÷ practical limit and reports the concentration = charge ÷ room volume, then passes when the charge is at or below the maximum for the room.
Frequently asked questions
What is a practical limit?
The practical limit is the maximum refrigerant concentration in an occupied space that BS EN 378 accepts for general occupancy, set by the refrigerant’s flammability or toxicity. Multiplying it by the room volume gives the largest charge that space can legally contain; the figures used here are the standard’s own Annex E values, carried forward under its grandfather clause.
Does this cover all occupancy types?
No. It applies to general occupancy (EN 378 Category A), the commonest and most restrictive case. Supervised (Category B) and authorised-access-only (Category C) occupancies can relax or remove the restriction. Leak-detection and ventilation alternative provisions and safety-group absolute charge caps are out of scope, shown as context rather than folded into the verdict.
What if the charge exceeds the limit?
The tool reports the minimum room volume the charge would need, so you can see how much larger the space must be, or split the system, reduce the charge, or move to a lower-GWP or lower-hazard refrigerant. It is a tender-stage practical-limit check under BS EN 378-1 Annex E; verify against a full EN 378 safety-classification assessment where required.