Multi-Split AC Refrigerant Guide UK: Charging, EN 378 Compliance and Servicing
Multi-split AC systems use significantly more refrigerant than single-splits, raising EN 378 A2L compliance and F-Gas record requirements. This guide covers what UK engineers need to know.
How Multi-Splits Differ from Single Splits
- Charge weight: A 4-zone R32 multi-split may contain 4–8 kg vs 0.6–1.4 kg for a single split
- EN 378 compliance: With R32, the 1.25 kg per occupied space limit applies per zone
- F-Gas threshold: 5 kg R32 = 3.4 tCO2e — below 5 tCO2e annual check threshold in most cases
- System complexity: Branch pipes, flow selectors, multiple TXVs — more potential leak points
EN 378 A2L Compliance for R32 Multi-Splits
The EN 378 charge limit of 1.25 kg per occupied residential space applies to each zone served. Assess each zone independently. If total R32 charge in a circuit serving one occupied space exceeds 1.25 kg, mechanical ventilation or a refrigerant detection device (RDD) is required.
Additional Charge Calculation
Multi-split additional charge typically includes: liquid line length beyond reference (g/m rate), number of indoor units beyond the base, and sometimes height difference. Always follow the manufacturer’s charge calculation procedure and log the final charge weight.
R32 9 kg from Refrigerant Gas Supplies Ltd — next-day UK delivery. See our R32 complete guide.
Frequently Asked Questions
Does a 4-zone R32 multi-split need F-Gas leak checks?
A 5 kg R32 multi-split = 3.4 tCO2e — below the 5 tCO2e threshold, so periodic checks are not legally required. F-Gas certification still needed to service it.
Can R32 multi-splits be installed in any UK room?
Yes, but EN 378 A2L 1.25 kg per occupied space limit applies. Exceed it and you need an RDD and mechanical ventilation in that space.
Can you top up an R32 multi-split if it loses charge?
Only after finding and repairing the leak. Add only the exact calculated amount by weight. Log all details in the F-Gas equipment record.