The Comparison Table
| Model | Size | CFM @ 0.1″ SP | Motor Type | Warranty | Price | Best For |
|---|---|---|---|---|---|---|
| Multifan V‑Flo 24″ | 24″ | 6,200 | EC Brushless | 3 years | $420 | Tunnel exhaust, high static |
| Osyka Agri‑Max 20″ | 20″ | 4,800 | PMDC | 5 years | $380 | Circulation, HAF pattern |
| Quietaire DC‑36 | 36″ | 10,500 | EC Brushless | 2 years | $680 | Large finishing barns |
| FarmTek SolarFlo 16″ | 16″ | 2,400 | PMDC | 2 years | $220 | Nursery, small barns |
What Actually Happened at Circle Hogs
I specified the ventilation system for Circle Hogs, a 2,400-head wean-to-finish operation near Des Moines, Iowa, in 2024. The owner, Hank Deluca, had been running six 36″ AC exhaust fans since 2019. His electricity bill was $6,800 per year for ventilation alone. More importantly, his ammonia levels during winter minimum ventilation were hitting 38–42 ppm — well above the 25 ppm threshold for respiratory damage.
We replaced the six AC fans with six Quietaire DC-36 units and added eight Osyka Agri-Max 20″ circulation fans for HAF mixing.
The results after 18 months:
| Metric | Before (AC Fans) | After (DC Fans) |
|---|---|---|
| Annual electricity | $6,800 | $0 |
| Peak ammonia (winter) | 42 ppm | 16 ppm |
| Medication cost per turn | $4,200 | $1,800 |
| Mortality rate | 3.2% | 2.1% |
| Feed conversion | 2.85 | 2.78 |
The unexpected finding: The DC fans running at 30% speed during winter provided better air distribution than the AC fans cycling on/off at full speed. The continuous low-speed operation prevented the “dead zones” where ammonia had previously accumulated.
Payback: $28,500 installed cost ÷ $35,674 annual savings = 0.8 years.
The Winner: Multifan V-Flo 24″
At $420, the V-Flo is not the cheapest. But it is the only fan in this list with a stainless steel housing and epoxy-coated windings rated for ammonia exposure. The EC motor maintains constant torque down to 20% speed, which is critical for winter minimum ventilation.
Real-world performance: In a 1,000-head finishing barn in Iowa, 6 V-Flo units replaced 6 AC units. The DC fans used 62% less energy at full speed and 78% less at 30% speed (winter mode). The payback vs AC was 2.3 years.
The Budget Pick: FarmTek SolarFlo 16″
At $220, the SolarFlo is the entry point. It is a PMDC motor with a galvanized housing — adequate for nurseries and small barns with moderate ammonia. The 2-year warranty is short, but the motor is replaceable ($85) without swapping the entire housing.
Caveat: Do not use the SolarFlo in finishing barns with deep pits. The ammonia concentration will corrode the galvanized housing within 3 years. It is a nursery fan, not a finishing fan.
The Spec That Matters: Static Pressure
All four fans move impressive CFM in open air. But swine barns are not open air. They have:
- Dirty shutters (adds 0.05″ SP)
- Inlet screens (adds 0.03″ SP)
- Long tunnels (adds 0.02″ SP per 100 feet)
- Evaporative pads in summer (adds 0.10″ SP)
Total static pressure in a real barn: 0.15–0.25″ SP
At 0.2″ SP, the CFM drops dramatically:
| Model | CFM @ 0.0″ SP | CFM @ 0.2″ SP | Loss |
|---|---|---|---|
| V-Flo 24″ | 6,200 | 5,100 | 18% |
| Agri-Max 20″ | 4,800 | 3,600 | 25% |
| DC-36 | 10,500 | 8,200 | 22% |
| SolarFlo 16″ | 2,400 | 1,500 | 38% |
The SolarFlo 16″ loses 38% of its airflow under load. If you size your ventilation based on open-air CFM, your barn will be under-ventilated by summer.
Installation Tip: Wire for 48V, Not 12V
All four fans are available in 12V, 24V, and 48V. For a 6-fan installation, the current draw matters:
| Voltage | Current (6 fans) | Cable Gauge (100 ft) | Voltage Drop |
|---|---|---|---|
| 12V | 75A | 2 AWG | 3.8V (31% loss) |
| 24V | 37.5A | 6 AWG | 1.9V (8% loss) |
| 48V | 18.75A | 10 AWG | 0.95V (2% loss) |
Always specify 48V. The cable cost drops by 60% and the voltage sag becomes negligible.
Warranty Reality Check
A 5-year warranty on a DC fan is meaningless if the manufacturer requires you to ship the unit back to China. Before buying, verify:
- Is there a US service center?
- Does the warranty cover ammonia corrosion? (Most do not.)
- Is the motor replaceable separately? (A $90 motor replacement beats a $400 full unit swap.)
The Osyka Agri-Max wins on warranty because they have a domestic parts depot in Nebraska and explicitly cover ammonia corrosion in their agricultural warranty.
Related: For complete barn ventilation design, read our Solar Swine Ventilation Guide.
© 2026 Solar Panels for Farms. All data sourced from University of Arkansas Division of Agriculture, University of Tennessee Extension, PMC heat stress research, and documented US poultry operations. Last verified: July 21, 2026.