Fan array calculator
Enter a single fan's rating and the array layout — columns, rows, spacing, wall clearance and partitions — and get the ideal array performance (AMCA 270) plus the AMCA 201 System Effect Factor from restricted inlets, with the corrected pressure requirement.
Two different questions, two different sources
"How much air does the array move?" and "how much of a pressure penalty does the layout cost you?" are answered by two different parts of the AMCA library, and this calculator keeps them separate rather than blending them into one made-up number.
Ideal array performance
For N identical fans operating in parallel at the same pressure, AMCA 201 Annex B.2 gives the combined characteristic as the sum of the individual airflows at that pressure: Qarray = N × Qfan, with power summed the same way. This is the number in every fan-array sales brochure — four 4,000 cfm fans "give" 16,000 cfm.
System Effect Factor — where a real number exists
AMCA 201 Section 7 quantifies how much of that ideal performance you actually lose to a restricted or asymmetrical inlet, with a real formula:
SEF = C × Pv, Pv = ρ V2 / 2
C is a coefficient (Table 7.1, 19 curves labelled F through X) read from Figure 9.11 by the ratio of clear wall-to-inlet distance to inlet diameter, L/D. This calculator applies that exact table and coefficient set — verified against AMCA 201's own worked example in Annex D.4 (Curve R, C = 1.20, Pv = 124.5 Pa → SEF = 149.4 Pa; Curve U, C = 0.40 → SEF = 49.8 Pa — both match exactly). A partition between two fans in the array is treated the same way, using half the clear fan-to-fan gap as the effective wall distance on each side.
Fan-to-fan spacing — where no numeric curve exists
AMCA 201 §9.6 gives a qualitative minimum for fan-to-fan proximity — at least one impeller diameter of clear space between adjacent axial fans, or between adjacent inlets of double-width centrifugal fans — but does not publish a graduated coefficient for spacing tighter than that. This calculator checks your spacing against that minimum and reports OK/WARNING; it does not invent a System Effect pressure for it, because AMCA 201 doesn't provide one.
What this does not do. Without the fan's full pressure-volume curve, this calculator can't solve for a corrected operating flow — only for the System Effect pressure that must be added to your system resistance calculation. Add the reported SEF to your ductwork losses when selecting the fan, or ask the manufacturer to verify performance at the SEF-adjusted point.