Size ductless mini-split heads and the outdoor unit for a multi-zone system.
Multi-zone systems exploit the fact that zones rarely peak simultaneously, so the outdoor unit is sized below the sum of the heads. Pushing diversity too low leaves zones unable to reach setpoint on design days. Mini-splits modulate, so slight oversizing is far less damaging than with single-stage equipment, but heavily oversized heads still cycle poorly at part load.
Mini-Split Sizing
Outdoor capacity = sum of head capacities × diversity factor
Outdoor capacity = sum of head capacities × diversity factor Multi-zone systems exploit the fact that zones rarely peak simultaneously, so the outdoor unit is sized below the sum of the heads. Pushing diversity too low leaves zones unable to reach setpoint on design days.
Mini-splits modulate, so slight oversizing is far less damaging than with single-stage equipment, but heavily oversized heads still cycle poorly at part load.
This calculator takes 5 inputs: Number of zones, Total conditioned area, Cooling intensity, Diversity factor, Seasonal efficiency ratio. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.