R-Pro › Field cases › Air conditioning
Multi-Split Distributor Pipe Sizing Imbalance → Capacity Deviation in Some Indoor Units
Likely causes
Branch pipe diameter mismatch — same-size branch connected to indoor units with different capacities
Check: Check manufacturer piping manual branch diameter table by capacity — e.g. 4.0 kW → Ø9.5 mm, 7.1 kW → Ø12.7 mm. Measure installed branch pipes and compare
What to do: Replace branch pipes in imbalanced sections — upsize piping by one size toward under-supplied indoor units → evacuate ≥30 min → recharge → during commissioning confirm discharge temperature deviation ±2°C
Equivalent length imbalance — certain indoor unit piping equivalent length exceeds 30 m causing excessive pressure drop
Check: Draw full piping diagram and calculate equivalent length for each indoor unit — convert elbows and valves to equivalent lengths. Check if difference between longest and shortest circuit exceeds 15 m
What to do: Measure liquid line pressure at each indoor unit outlet — if deviation ≥0.05 MPa, replace branch pipes or redesign routing. Add U-shaped oil traps in vertical drop sections >15 m (one per 10 m interval)
After multi-split installation, commissioning must confirm discharge temperature deviation ±2°C per indoor unit — a larger deviation signals piping imbalance.
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