A2L Refrigerant Charge Limit Calculator

Inputs

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A2L refrigerant; sets the lower flammability limit (LFL).
Release height of the indoor unit — sets h0 in the UL 60335-2-40 relation.
Floor area of the smallest room served by the indoor unit.
m²
Total installed refrigerant charge of the system (factory + line-set).
kg

Results

Default result
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Max allowable charge(m_max)
1.434kg
Pass

within the limit for this room — no extra mitigation required by this relation

Also computed

Min room area for charge(A_min)Pass14.01m²

smallest room that accepts the installed charge

Method notes 5 notes
  • LFL = 0.291 kg/m³, release height h₀ = 0.6 m.
  • m_max = 2.5 · LFL^1.25 · h₀ · √A (UL 60335-2-40 / IEC 60335-2-40, A2L comfort cooling).
  • A_min = (m / (2.5 · LFL^1.25 · h₀))² is the smallest room floor area that accepts the installed charge without extra mitigation.
  • Area-based relation only: charges below m1 = LFL · 4 m³ need no room-area check, and m2/m3 upper caps apply above it — so for small rooms this can read more conservative than the standard requires. Verify against the current edition.
  • Screening only — NOT a substitute for the manufacturer installation manual, the current edition of the standard, or your AHJ. Above the limit you may still comply with a refrigerant detection system (RDS) / airflow mitigation per UL 60335-2-40.

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