Data Center Fan Selection: Why Your CRAC Unit's Factory Fan Might Be Wrong

Jun 12, 2026

By Dannis Luo · Fanova Application Engineering · June 12, 2026 · 7 min read

A colocation provider in Frankfurt replaced six CRAC units in two years. Every single one ran hotter than spec. When we pulled a fan module, the issue was obvious: the factory fan was sized for open-plenum lab conditions, not for their raised-floor duct resistance.

This is common. Here's how to match fans to real data center conditions.

1. The System Curve Always Wins

Every fan ships with a performance curve. But your data center adds filters, coils, dampers, and ducts — each adding resistance. The operating point is where the fan curve meets the system resistance curve.

Bench data: An FK3G310-4APK-60 (310mm backward curved, 380VAC) delivers 4,000 m³/h at 0 Pa on our test bench. Behind a MERV-13 filter and chilled-water coil (about 180 Pa), the operating point shifts to roughly 2,600 m³/h — a 35% reduction.

2. Axial vs. Centrifugal — It's About Pressure

Fan Type	Best For	Pressure Range	Fanova Series
Axial (EC)	In-row coolers, rear-door HX	0-135 Pa	FG3G350
Forward curved centrifugal	CRAC with moderate static	50-350 Pa	FF3G
Backward curved centrifugal	CRAH, raised floor, ducted	100-1,000 Pa	FB3G / FK3G

3. EC vs. AC — Real Numbers

An AC induction fan at fixed speed draws full power regardless of load. An EC fan with 0-10V control ramps down when the data center is at 40% load at 3 AM.

	AC Fan (belt-drive, 3hp)	EC Fan (FK3G310-4APK-60)
Power @ full load	2,240 W	790 W
Power @ 60% speed	2,240 W (fixed)	~170 W (variable)
Annual energy (8,760h, 60% part-load)	19,622 kWh	~3,900 kWh
Annual cost @ $0.12/kWh	$2,355	~$468

About $1,887/year savings per fan. A 10-fan CRAC retrofit recovers hardware cost in under 12 months. Plus zero belt replacements — roughly $200/year/unit in maintenance eliminated.

4. Fan Arrays: N+1 Without Oversizing

Instead of one large blower, install four FW3G200-2AGS-70 (200mm axial, 1,205 m³/h each) in parallel. Each runs at 75%. If one fails, the remaining three ramp to 100%. No downtime. A single fan hot-swaps in 15 minutes.

Quick Reference

Use Case	Recommended Fan	Key Spec
CRAC retrofit, raised floor, filtered	FK3G310-4APK-60	380VAC, 4,000 m³/h, 1,000 Pa, 84 dBA
CRAC retrofit, 230VAC	FK3G310-2APK-20	230VAC, 3,721 m³/h, 950 Pa, 81 dBA
In-row cooler, low-pressure	FG3G350-2APN-90	230VAC axial, 3,500 m³/h, 135 Pa, 63 dBA
Rear-door heat exchanger	FW3G200-2AGS-70	230VAC axial, 1,205 m³/h, 250 Pa, 62 dBA
Fan wall, N+1 array	FB3G400-2APK-20	230VAC, 5,755 m³/h, 785 Pa, 80 dBA