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Views: 264 Author: Capital Technology Publish Time: 2026-10-06 Origin: Site
Content Menu
● What Is a San Ace Counter Rotating Fan?
● How the Airflow Principle Differs
>> Conventional DC Fan Airflow
>> Counter Rotating Fan Airflow
● San Ace Counter Rotating Fan vs Conventional DC Fan
● Static Pressure: The Deciding Factor in Dense Electronics
>> Why High Static Pressure Matters
● Performance Comparison at the System Operating Point
>> A Simple Engineering Example
● San Ace Counter Rotating Fan Performance Examples
● Noise, Power, and Control: The Trade-Offs
>> Power Consumption Considerations
● Installation Space and Mechanical Integration
>> Practical Airflow Design Tip
● Reliability and Maintenance Considerations
>> Reliability Selection Checklist
● When Should You Choose a Conventional DC Fan?
● When Should You Choose a San Ace Counter Rotating Fan?
● A Practical Selection Process for OEM Projects
● FAQ
>> 1. What is a counter rotating fan?
>> 2. Is a counter rotating fan better than a conventional DC fan?
>> 3. Why is static pressure important in a cooling fan?
>> 4. Can San Ace counter rotating fans reduce system noise?
>> 5. Are San Ace counter rotating fans suitable for servers?
>> 6. Do counter rotating fans consume more power?
>> 7. What information is needed to select the right DC fan?
When thermal design space becomes limited, choosing the right fan is no longer a simple airflow comparison. A San Ace counter rotating fan and a conventional DC fan may both use DC power and axial airflow, but they are built for very different cooling challenges.
In practical equipment design, the key question is not simply, "Which fan has a higher CFM rating?" It is: Which fan can maintain useful airflow after it meets the resistance of heatsinks, filters, narrow ducts, dense PCBs, and high-power electronic components? For compact servers, telecom cabinets, network switches, power supplies, and industrial control systems, a counter rotating fan can provide a major thermal advantage.
As a cooling-solution manufacturer and a chief SANYO DENKI distributor, Capital Technology Co., Limited works with customers who must balance thermal performance, available installation space, system noise, reliability, and total operating cost. This guide explains how San Ace counter rotating fans differ from conventional DC fans and how to select the right solution for demanding electronics cooling projects.
A San Ace counter rotating fan is a high-performance axial DC fan system with two impellers arranged in series. The inlet-side impeller and outlet-side impeller rotate in opposite directions.
This counter-rotation design helps recover and redirect the swirling airflow discharged by the first impeller. Instead of allowing much of that rotational energy to be lost, the second impeller converts more of it into useful airflow and static pressure.
A conventional DC fan usually has:
- One motor
- One impeller
- One airflow stage
- A comparatively simple frame and driver structure
A counter rotating fan usually has:
- Two impellers
- Two independently driven rotating stages
- One integrated fan assembly
- A deeper body than a typical single-stage axial fan
- Higher airflow and static-pressure capability for restricted systems
San Ace counter rotating fan designs are especially suitable for equipment with high mounting density. In these systems, heat generation rises while the space available for cooling components becomes smaller.
The basic difference between a conventional DC fan and a counter rotating fan is the way each design manages airflow energy.
A conventional DC fan creates airflow through one rotating impeller. It pulls air into the fan, accelerates it, and sends it downstream.
This design is efficient and practical for many systems. It works well when the airflow path is relatively open.
However, the discharged air often contains rotational motion, also called swirl. In a low-resistance environment, this may not cause a serious problem. But in a highly restricted chassis, that swirl can reduce the amount of useful forward airflow available to overcome resistance.
A counter rotating fan uses a second impeller spinning in the opposite direction.
The first impeller moves air forward. The second impeller receives that airflow and counteracts the rotational component created by the first stage. This can improve the pressure-generating ability of the complete assembly.
The result is not merely "two fans in one housing." It is a coordinated two-stage airflow system designed for demanding operating points.
This is why counter rotating fans are often selected for high-impedance cooling paths rather than open-air ventilation.
The following table summarizes the most important differences for design engineers, procurement teams, and equipment manufacturers.
| Comparison Factor | San Ace Counter Rotating Fan | Conventional DC Fan |
|---|---|---|
| Basic structure | Dual impellers rotating in opposite directions | One impeller rotating in one direction |
| Airflow stages | Two-stage airflow generation | Single-stage airflow generation |
| Static pressure capability | Usually much higher for the same compact footprint | Lower to moderate, depending on model |
| High-impedance performance | Strong performance through dense system resistance | Performance may decrease sharply as resistance rises |
| Suitable applications | Servers, telecom equipment, switches, storage systems, power supplies | General electronics, open enclosures, light-duty ventilation |
| Axial length | Usually thicker than a standard single fan | Usually more compact in depth |
| Noise potential | Can be higher at full speed | Often easier to keep quiet at lower duty points |
| Power consumption | May be higher at maximum performance | Often lower in basic low-pressure applications |
| Control functions | Many models support PWM speed control and tachometer output | PWM and tachometer depend on the fan model |
| System design value | Helps reduce the number of fan positions in severe thermal layouts | Simple, economical solution for moderate cooling demands |
The most important point is that a counter rotating fan should not be judged only by free-air CFM. Its real value appears when the fan operates against system impedance.
Many purchasing decisions focus on airflow, usually expressed in CFM or \(m^3/min\). Airflow is important, but it is not enough.
A fan's maximum airflow rating is usually measured under nearly unrestricted conditions. Real equipment rarely operates that way.
Air must often move through:
- Tight heatsink fins
- EMI shielding
- Air filters
- Cable assemblies
- Narrow chassis openings
- Memory modules and daughter boards
- Power modules
- High-density PCB layouts
- Long or complex air ducts
Each obstacle creates pressure loss. The fan must produce enough static pressure to keep airflow moving through the system.
A high-static-pressure fan can sustain airflow as system resistance increases. This is especially important in compact electronics where the air path cannot be widened.
For example, the San Ace 60 9CRH type counter rotating fan measures 60 × 60 × 56 mm and is specified with maximum airflow of 90.8 CFM and maximum static pressure of 13.4 inches H₂O. This makes it a strong candidate for compact high-performance systems where conventional axial fans may struggle to push air through restrictive internal components.
By comparison, a conventional DC fan can be a better choice when:
- The enclosure has open venting
- Airflow resistance is low
- Acoustic output must be minimized
- The system thermal load is moderate
- Installation depth is extremely limited
- Budget is the primary driver
The correct selection depends on the operating point, not only the catalog headline specification.
The fan curve is one of the most valuable tools in fan selection.
A fan curve shows the relationship between airflow and static pressure. As static pressure rises, airflow normally falls. The actual operating point is where the fan curve meets the system-resistance curve.
Imagine two cooling designs inside a compact network switch:
- Design A uses a conventional DC fan.
- Design B uses a San Ace counter rotating fan.
- Both systems have the same fan mounting area.
- Both systems include restrictive heatsinks, front-panel vents, and dense PCB components.
In open air, the conventional fan may appear sufficient. But once it is installed in the switch, resistance reduces its actual airflow.
The counter rotating fan is designed to generate more pressure. It can therefore maintain a higher airflow level when the system resistance rises.
This can create several benefits:
- Lower component temperatures
- More stable cooling across the chassis
- Better thermal margin during high ambient conditions
- Reduced risk of thermal throttling
- Potentially fewer fan positions in a compact layout
For equipment designers, thermal margin is valuable because actual field conditions are rarely identical to a laboratory test environment.
San Ace counter rotating fan models are available in multiple frame sizes, voltages, and performance levels. The correct model should always be selected based on thermal testing, voltage requirements, installation depth, noise limits, and reliability targets.
| Example Model Type | Frame Size | Typical Application Direction | Key Selection Value |
|---|---|---|---|
| San Ace 40 counter rotating fan | 40 mm class | Compact network devices, small power modules, dense controllers | High pressure in very limited mounting space |
| San Ace 60 counter rotating fan | 60 mm class | Telecom equipment, server subsystems, high-density electronics | Strong airflow and pressure balance |
| San Ace 80 counter rotating fan | 80 mm class | Larger server and communications systems | High cooling capacity for high thermal loads |
| San Ace 120 counter rotating fan | 120 mm class | Industrial systems, power equipment, storage and network platforms | High airflow for larger restricted air paths |
A 60 mm counter rotating San Ace model can achieve high output despite its compact footprint. For engineers working with narrow 1U or similarly space-constrained designs, this performance density can be more valuable than using a larger conventional fan that cannot fit inside the enclosure.
A counter rotating fan is a specialized cooling solution. It can solve severe thermal problems, but it also requires a balanced evaluation.
High rotational speed and high pressure generation can increase acoustic output. A counter rotating fan running at maximum speed may produce more noise than a conventional DC fan operating at a moderate speed.
However, the real comparison should be made at the required thermal operating point.
A conventional fan may need to run close to its maximum speed to produce enough airflow through a restrictive system. A properly controlled counter rotating fan may maintain cooling more effectively and adjust speed based on temperature demand.
Many San Ace counter rotating models support PWM control, allowing the system to adjust fan speed dynamically.
PWM control can help equipment manufacturers:
- Reduce fan speed during lower thermal loads
- Lower noise during normal operation
- Reduce unnecessary power consumption
- Extend bearing life by avoiding constant maximum-speed operation
- Improve user comfort in office, telecom, and enterprise environments
A high-performance counter rotating fan can consume more power than a standard single-stage DC fan. This is expected because it uses two rotating stages to deliver stronger cooling capability.
The right comparison is not fan input power alone. Instead, consider:
- Cooling capacity per installation area
- Cooling capacity at the required static pressure
- Number of fans required in the full system
- Temperature reduction achieved
- Reliability value of lower component temperatures
- Power savings enabled through PWM control
In some systems, one high-performance counter rotating fan can reduce the need for multiple weaker fans. This may simplify mounting, wiring, monitoring, and airflow management.
A conventional DC fan is often easier to integrate because it has a simpler structure and shorter axial depth.
A counter rotating fan usually requires more depth. For example, a compact 60 mm counter rotating fan may be 56 mm thick, which is significantly deeper than many standard 60 mm axial fans.
Before specifying a counter rotating fan, confirm:
1. Available depth inside the enclosure
2. Mounting-hole compatibility
3. Inlet and outlet clearance
4. Cable routing space
5. Connector type and wire length
6. Power supply capacity
7. Controller compatibility for PWM and tachometer signals
8. Vibration and mechanical support requirements
Do not install a high-performance fan directly against a blocked intake or exhaust opening. Even a strong counter rotating fan cannot compensate for poor chassis vent design.
Keep obstructions away from the fan inlet and outlet whenever possible. A short clearance gap can help reduce turbulence and improve usable airflow.
Also review the entire cooling path. A high-pressure fan works best when the air route is intentional:
- Cool air enters through a low-resistance intake.
- Air moves directly across heat-generating components.
- Hot air exits through a properly sized exhaust path.
- Recirculation zones are minimized.
For professional electronics cooling, reliability is not limited to fan runtime. It includes stable operation under temperature, voltage, dust, vibration, and continuous-duty conditions.
San Ace counter rotating fan specifications commonly include expected-life ratings under defined operating conditions. For example, specific models are rated for 40,000 hours at 60°C under rated voltage and continuous operation in free air, based on an L10 life definition.
This matters because server, telecom, industrial, and communications equipment may run continuously for years.
When comparing a San Ace counter rotating fan with a conventional DC fan, review:
- Expected life rating
- Operating temperature range
- Bearing system
- Locked-rotor protection
- Pulse sensor or alarm output
- PWM speed-control capability
- Ingress-protection requirement
- Voltage tolerance
- RoHS and material requirements
- Supply continuity and technical support
For critical equipment, it is also wise to evaluate fan monitoring at the system level. A tachometer signal can help the controller detect abnormal fan speed and trigger an alarm before overheating becomes a major issue.
A conventional DC fan remains the best option in many applications.
Choose a standard DC fan when your system has:
- Low airflow resistance
- Moderate heat generation
- Sufficient installation space for multiple fans
- Tight acoustic requirements
- Lower power budget
- Cost-sensitive volume production
- Simple speed-control requirements
Typical applications include:
- Consumer electronics
- Standard control cabinets
- Light-duty industrial equipment
- Open-frame power supplies
- General ventilation modules
- Low-density PCB enclosures
A conventional DC fan is not an inferior product. It is simply optimized for a different operating environment.
A San Ace counter rotating fan is worth considering when the cooling problem is defined by resistance, density, and limited space.
Choose a counter rotating solution when your equipment has:
- High system impedance
- Narrow or obstructed air channels
- Compact chassis dimensions
- High-power processors or switching components
- Dense heat sinks
- High ambient-temperature requirements
- Demanding uptime expectations
- A need for PWM-based thermal control
- Limited fan mounting positions
Typical applications include:
- High-end servers
- Telecom base-station equipment
- Network switches and routers
- Storage systems
- High-density power supplies
- Industrial communication systems
- Medical electronics
- Data-center infrastructure
- Advanced automation controllers
For these applications, the right fan can affect component temperature, product reliability, acoustic behavior, and long-term service cost.
The best way to choose between a San Ace counter rotating fan and a conventional DC fan is to follow a structured thermal design process.
1. Calculate the heat load
Identify the wattage generated by processors, power modules, transceivers, memory, and other heat-producing components.
2. Map the airflow path
Identify all restrictions, including filters, heatsinks, vent patterns, cable bundles, and board spacing.
3. Estimate system impedance
Use CFD analysis, prototype testing, or measured pressure-drop data where available.
4. Review fan curves instead of only maximum CFM
Select a fan that delivers adequate airflow at the real pressure operating point.
5. Check installation dimensions
Confirm fan depth, mounting, electrical interface, and clearance requirements.
6. Evaluate noise at actual operating speed
Do not compare noise levels only at maximum speed. Review expected duty conditions.
7. Use PWM control when appropriate
Dynamic speed control can improve thermal efficiency, acoustic comfort, and energy use.
8. Validate with prototype testing
Measure component temperatures, inlet and outlet temperatures, airflow direction, and fan speed under realistic load conditions.
Capital Technology can support this process with fan selection guidance, product availability, and cooling-solution experience for OEM and industrial equipment projects.
The main difference between a San Ace counter rotating fan and a conventional DC fan is not simply the number of impellers. It is the ability to maintain strong cooling performance under resistance.
A conventional DC fan is often ideal for open or moderately restricted equipment. It is compact, economical, and easy to integrate.
A San Ace counter rotating fan is designed for more severe thermal conditions. Its dual-stage, counter-rotating structure can deliver high airflow and high static pressure in a compact mounting area. That makes it a valuable solution for high-density servers, telecom equipment, power systems, and other electronics where cooling space is limited but thermal demand is high.
For a new project, select the fan based on the complete system operating point—not only free-air airflow. A well-matched fan can improve thermal margin, reduce overheating risk, and support more reliable equipment operation.
Contact Capital Technology Co., Limited to discuss your system airflow resistance, voltage, size constraints, and cooling targets. Our team can help identify whether a San Ace counter rotating fan or a conventional DC fan is the better fit for your design.
A counter rotating fan uses two impellers that rotate in opposite directions. The second impeller helps manage the airflow created by the first stage, supporting higher airflow and static pressure in restrictive cooling systems.
Not in every application. A counter rotating fan is generally better for high-resistance and high-density cooling paths. A conventional DC fan is often more suitable for open-air, low-pressure, low-noise, or cost-sensitive applications.
Static pressure shows how effectively a fan can push air against resistance. Higher static pressure is important when air must pass through heatsinks, filters, narrow vents, dense PCBs, and other obstructions.
They can help reduce noise when used with PWM speed control and correctly matched to the actual cooling demand. However, at full speed, high-performance counter rotating fans may produce more noise than a standard low-speed DC fan.
Yes. They are designed for high-density applications such as servers and telecom equipment, where strong airflow and high static pressure are needed in limited installation space.
They may consume more power at maximum performance because they use two rotating stages. However, the full system should be evaluated. In some cases, one counter rotating fan can replace several lower-performance fans or improve cooling efficiency under high resistance.
Useful selection information includes the required voltage, available installation space, airflow target, system static pressure, maximum acceptable noise level, operating temperature, life requirement, connector type, and PWM or alarm-signal requirements.
1. SANYO DENKI. "[Counter Rotating Fan | San Ace Cooling Systems]." Product overview covering the design purpose, high-airflow and high-static-pressure characteristics, and PWM control benefits of San Ace counter rotating fans. [products.sanyodenki]
2. SANYO DENKI. "[Counter Rotating Fan Lineup | San Ace]." Product lineup and specifications for counter rotating fan models, including frame sizes, airflow, static pressure, sound-pressure levels, expected life, pulse sensors, and PWM availability. [products.sanyodenki]
3. SANYO DENKI. "[SANYO DENKI Develops 60 × 60 × 56 mm Counter Rotating Fan with the Industry's Highest Static Pressure and Airflow]." June 20, 2024 product release with specifications for San Ace 60 9CRH models, including 90.8 CFM maximum airflow, 13.4 inches H₂O maximum static pressure, 78 dB(A) sound-pressure level, and 40,000-hour expected life at 60°C. [sanyodenki]
4. SANYO DENKI. "[DC Fan Catalog]." Product catalog outlining the San Ace DC fan range, including low-power, low-noise, high-airflow, and high-static-pressure fan categories. [sanyodenki]
5. SANYO DENKI. "[SANYO DENKI Develops 80 × 80 × 80 mm Counter Rotating Fan]." Product release describing the San Ace 80 9CRHA counter rotating fan, including 199 CFM airflow and 10.8 inches H₂O static pressure specifications. [sanyodenki]
6. SANYO DENKI. "[High Air Flow and High Static Pressure Counter Rotating Fan San Ace 172 CR Type]." Technical report describing high airflow, high static pressure, lower-power operating-point performance, and PWM control in a counter rotating fan design. [sanyodenki]
