Minimum room volume and charge limit

Basic flammability screening · EN 378-1

Scenario: refrigeration in an occupied space
Refrigeration other than human comfort, location I, general access (category a), without alternative provisions. For A3 refrigerants, only sealed systems are covered. This concentration and charge check alone does not establish EN 378 compliance.

Room and circuit parameters

R455A · A2L

Reference LFL : 0.431 kg/m³

Concentration threshold (20% LFL or a more conservative published value) : 0.086 kg/m³

Total charge that could be released into the room. Multiple circuits, isolation devices and releasable charges require a specific assessment.
Use the smallest occupied space where a leak could occur, following the rules for connected rooms. Do not automatically add rooms together.

Confirm with the manufacturer: sealed system is a defined normative term, not simply a circuit without leaks.

For A3 refrigerants with general access, the charge cap in this scenario changes from 1.5 kg to 1 kg.

30 %

Personal margin of 0–100% added to the calculated volume (× 1.30 for 30%). It does not change the concentration threshold or the charge cap.

Results update automatically. Ambient temperature is not used to recalculate reference concentrations.

Basic screening results

Concentration threshold exceeded
The room volume is insufficient for this charge in the basic scenario. Reduce the charge, increase the admissible volume or assess applicable alternative provisions.

Minimum volume based on the concentration threshold

34.89 m³

With the desired additional volume : 45.35 m³

Charge limit for this room and scenario

2.58 kg

Charge cap independent of room volume

16.809 kg

Theoretical average concentration (charge / volume) : 0.1 kg/m³

Concentration threshold usage : 116.3 %

100% means the screening threshold, not the LFL. This average does not describe local accumulation during a leak.

Volume = charge / threshold : 3 / 0.086

Charge limit = minimum (volume × threshold; cap) : min(30 × 0.086 ; 16.809)

Displayed volumes are rounded up and charge limits down. Comparisons use unrounded values.

If your installation falls under another scenario

Exceeding this basic check does not rule out every configuration. The following possibilities require checking their applicability.

  • Reducing charge or using independent circuits may reduce the releasable charge. Room volume and connections between rooms must be admissible under the standard.
  • For some A2L systems, Annex C.3 alternative provisions allow assessment using QLMV / QLAV, detection, ventilation, alarms or isolation. Adding a detector alone does not automatically make an installation acceptable.
  • An outdoor compressor (location II), machinery room, indirect system or supervised/restricted access can change limits and requirements. Low occupancy density may also allow another scenario; none of these scenarios is applied here.
  • Comfort air conditioning and heat pumps involve floor area, installation height and small-charge thresholds. Room volume alone is insufficient: follow the standard and manufacturer calculation path.
  • Check the applicable product standard, including EN IEC 60335-2-40 or EN IEC 60335-2-89, and manufacturer instructions. Its conditions may determine the assessment path.

This checks flammability only. Also assess toxicity / oxygen deprivation, local accumulation, ignition sources, ventilation, design, installation, operation and the other parts of EN 378.

Method and references

Basic method: concentration threshold ≤ 20% LFL; A2L charge cap = 1.5 × 26 m³ × LFL. Published values of 0.061 and 0.086 kg/m³ are used for R32 and R455A. For sealed R290 systems with general access: a 1.5 kg cap above ground or 1 kg below ground.

Path based on EN 378-1:2016+A1:2020 and the stated references. Confirm the edition applicable to the project and current manufacturer data. Volume percentages and saturated-vapour densities are not used in this calculation.

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