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Featuring advanced aerodynamic design measures such as Flow Acceleration Channels and Noctua’s AAO frame, the NF-A4x20 is a highly optimised, premium-quality quiet fan in size 40x20mm. The PWM version sports Noctua’s custom-designed NE-FD1 IC for fully automatic speed control via 4-pin fan headers and comes with a Low-Noise Adaptor as well as an OmniJoin™ Adaptor Set for easy connection to proprietary fan headers. Its superb running smoothness, reference-class SSO2 bearing and Noctua’s trusted premium quality make it an elite choice for the highest demands.
Details
40x20mm size

40x20mm size

Compared to Noctua’s award-winning NF-A4x10, the NF-A4x20 is twice as thick, which allows for increased static pressure performance and makes the NF-A4x20 ideal for demanding applications with high flow resistance.
Flow Acceleration Channels

Flow Acceleration Channels

The NF-A4x20 impeller features suction side Flow Acceleration Channels. By speeding up the airflow at the crucial outer blade regions, this measure reduces suction side flow separation and thus leads to better efficiency and lower vortex noise.
AAO Frame

AAO Frame

Noctua's AAO (Advanced Acoustic Optimisation) frames feature integrated anti-vibration pads as well as Noctua's proprietary Stepped Inlet Design and Inner Surface Microstructures, both of which further refine the fan's performance/noise efficiency.
Stepped Inlet Design

Stepped Inlet Design

Noctua's Stepped Inlet Design adds turbulence to the influx in order to facilitate the transition from laminar flow to turbulent flow, which reduces tonal intake noise, improves flow attachment and increases suction capacity, especially in space-restricted environments.
Inner Surface Microstructures

Inner Surface Microstructures

With the tips of the fan blades ploughing through the boundary layer created by the Inner Surface Microstructures, flow separation from the suction side of the blades is significantly suppressed, which results in reduced blade passing noise and improved airflow and pressure efficiency.
Integrated Anti-Vibration Pads

Integrated Anti-Vibration Pads

Integrated Anti-Vibration Pads made from extra-soft silicone minimise the transmission of minute vibrations while maintaining full compatibility with all standard mounting systems and fan clips used on heatsinks.
SSO2 bearing

SSO2 bearing

The NF-A4x20 features the further optimised second generation of Noctua's renowned, time-tested SSO bearing. With SSO2, the rear magnet is placed closer to the axis to provide even better stabilisation, precision and durability.
Custom-designed PWM IC with SCD

Custom-designed PWM IC with SCD

Supporting fully automatic PWM speed control, the fan uses Noctua's custom-designed NE-FD1 PWM IC that integrates Smooth Commutation Drive (SCD) technology. By providing smoother torque impulses, SCD suppresses PWM switching noises and thus makes the fan quieter at low speeds.
Low-Noise Adaptor

Low-Noise Adaptor

The NF-A4x20 PWM is supplied with a (L.N.A.) that reduces the maximum fan speed from 5000 to 4400rpm. The L.N.A. can be used either to run the fan at a fixed speed of 4400rpm or to cap the maximum speed when using automatic PWM control.
OmniJoin™ adaptor set

OmniJoin™ adaptor set

Many devices featuring 40mm fans use proprietary fan headers, so the NF-A4x20 comes with Noctua's OmniJoin™ adaptor set. Just cut the original fan's cable, fix it to the adaptor using the supplied 3M Scotchlok™ connectors and you can plug the NF-A4x20 to proprietary fan headers!
Extensive cabling options

Extensive cabling options

The fan's short 20cm primary cable minimises cable clutter in typical applications while the supplied 30cm extension provides extended reach when necessary. Both cables are fully sleeved and a 4-pin y-cable allows the connection of a second fan to the same PWM fan header for automatic control.
6-year manufacturer’s warranty

6-year manufacturer’s warranty

Noctua fans are renowned for their impeccable quality and outstanding longevity. Like all Noctua fans, the NF-A4x20 features an MTTF of more than 150.000 hours rating and comes with a full 6-year manufacturer’s warranty.
NF-A4x20 PWM
FAN Specification
Size
40x40x20 mm
Mounting hole spacing
32x32 mm
Connector
4-Pin PWM
Bearing
Blade Geometry
Rotational Speed (+/- 10%)
5000 RPM
Rotational Speed with L.N.A. (+/- 10%)
4400 RPM
Min. Rotational Speed (PWM, +/-20%)
1200 RPM
Acoustical Noise
14,9 dB(A)
Acoustical Noise with L.N.A.
12,2 dB(A)
Static Pressure
2,26 mm H₂O
Static Pressure with L.N.A.
1,75 mm H₂O
Max. Input Power
0,6 W
Max. Input Current
0,05 A
Voltage
12 V
MTTF
> 150.000 h
Scope of Delivery
  • Low-Noise Adaptor (L.N.A.)
  • 4-pin y-cable
  • 30cm extension cable
  • OmniJoin™ adaptor set
  • NA-AV3 anti-vibration mounts
  • Fan screws
Warranty
6 years
NF-A4x20 PWM
A-Series fans
Video Reviews
The following video reviews have not been created by Noctua. Responsibility for the information and views expressed in the videos lies entirely with the authors.
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17.06.2017 // XtremeSystems.org
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NF-A4x20 PWM Review

If you are in the market for 40mm new fans the new offerings from Noctua will not let you down. They follow in the same footsteps of those before them and are helping to grow Noctua’s legacy as a leader in cooling solutions.
Test verdict: "If you need good air flow, low noise and have a rack mounted server, router, DVR, media player and NAS enclosure that needs some better fan, I could definitely recommend what Noctua has to offer here." (Ambrosidou Nat, XtremeSystems.org)
16.06.2017 // TechHardware.it
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NF-A4x20 PWM Review

Le ventole Noctua A-Serie che andremo ad analizzare quest’oggi, è stata ufficialmente presentata a Vienna poche settimane fa (precisamente il 17 Maggio). Questa serie di ventole, come specificato da Roland Mossing CEO di Noctua, è stata più volte richiesta dai propri clienti al fine di colmare un gap di tipologia di ventole presenti. Basate sul più avanzato sistema SSO2 Bearing, questa serie di ventole integra il massimo dei brevetti e dello studio degli ingegneri Noctua. Integra infatti anche un design delle ventole di tipo AAO (Advance Acousting Optimisation) che permette di ridurre ulteriormente il rumore. Il colore di struttura, pale e supporti antivibrazione riprendono appieno lo standard delle versioni premium dell’azienda svizzera, ovvero beige per la struttura e marrone per pale e supporti antivibrazione.
Test verdict: "Eccellente il lavoro svolto anche in questo caso dall'azienda Australiana, è riuscita a produrre e commercializzare prodotti davvero validi riuscendo a mantenere prezzi competitivi con questa A-Serie." (Tommaso Biallo, TechHardware.it)
13.06.2017 // Glob3trotters.com
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NF-A4x20 PWM Review

What more can you say when you see examples of dedication and perseverance to bring maximum quality and performance on all fronts! This is what we discovered in our testing for Noctua’s new A-Series lineup that excels in both new technologies, refinement of the existing proprietary ones, static pressure, airflow and noise output. Some of the test that we employed are extreme/exaggerated scenarios but the fans still managed to come ahead with flying colors.
Test verdict: "Noctua’s new A-series is defiantly an overall winner because it brings new features to the table without sacrificing what was good in the past models plus further refining those as well." (Alex Nistor, Glob3trotters.com)
06.06.2017 // HWready.it
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NF-A4x20 PWM Review

Le soluzioni da 20 cm sono riuscite a far calare di 15 gradi la temperatura in un case areato con tre ventole da 12 cm, abbassandone anche la rumorosità finale. Le ventole da 12 cm spesse solo 1.5 cm sono quel che ci voleva per riuscire ad installare in case che non lo prevedono anche radiatori più spessi, mantenendo prestazioni superiori a tante ventole da 12 cm. Le piccole ventole da 4 cm sono curate nei dettagli e vantano bundle di tutto rispetto, mi sento di consigliarle vivamente a chi installa SSD m2. Per quanto riguarda gli accessori invece gli anti vibrazione come al solito si comportano benissimo, essi sono utilizzabili su quasi tutte le ventole in commercio e riducono sensibilmente ogni tipo di movimento, oltre a permettere una installazione più veloce e senza cacciavite. Il controller fan piccolo e potente permette di spingere fino a tre ventole ed è dotato di prolunga, utilissimo.
Test verdict: "Siamo giunti alla fine della nostra recensione, ogni qual volta mettiamo le mani su un prodotto Noctua ci accorgiamo dell’enorme cura che il produttore Austriaco mette nei particolari. Ogni singola ventola è accompagnata da un bundle che permette all’utente finale di sfruttarla al meglio. Le prestazioni di questi prodotti sono come sempre al top e non temono confronto con nessun prodotto sul mercato." (Mauro Santoro, HWready.it)
06.06.2017 // HardwareMAX.it
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NF-A4x20 PWM Review

Cari amici di HM siamo giunti alle conclusioni, le nuove ventole A-Series si sono rivelate delle ottime ventole sia per i materiali che per la costruzione, e sopratutto per la loro funzionalità che le rende particolarmente potenti con ottimi flussi d’aria e sopratutto per la loro silenziosità. Ottimo il nuovo approccio di Noctua con ventole da 20 cm e con la rinnovata serie da 12 cm, ma con uno spessore di soli 15 mm, che le rendono particolarmente interessanti sopratutto per chi ha problemi di spazio. Non ci resta che consigliarne l’acquisto a chi mira ad un’ottima efficienza ed allo stesso tempo vuole il massimo della silenziosità. L’unico appunto che potremmo fare è sulla colorazione delle ventole, che a molti utenti non piace, ma che sicuramente la contraddistingue, sarebbe ottimo avere anche delle versioni con LED RGB per chi vuole fare modding.
Test verdict: "Le ventole Noctua A-Series sono ben costruite ed assicurano una buona efficienza ed un bassissimo rumore." (Da Igor Lucifaro, HardwareMAX.it)
05.06.2017 // PCnet.com.tr
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NF-A4x20 PWM Review

Senelerden beri yüksek kaliteli ve düşük gürültülü soğutma sistemleri sunan Noctua, işlemci soğutucularına ek olarak fanlar da satmakta ve bunlar öncelikli olarak kasa fanı olarak tercih edilmekteydi. Zaman içinde 80/90/120mm klasik fanlara 140mm geniş modeller ve sonrasında 60 ve 40mm alt modeller eklenmişti. Firma bir adım daha ileri atarak en sonunda 200mm fanlar da sundu. Aynı zamanda daha önceki 40x40x10mm fanlara 20mm kalınlıklı versiyon ve 120x120x25mm fanlara 15mm kalınlıklı ince versiyonlar eklendi. Şimdi bu yeni fanlara ve aksesuarlara bakış atıyoruz.
Test verdict: "Kaliteden asla ödün vermeyen Noctua'nın yeni fanları ve aksesuarları ürün gamını genişletiyor ve eksik modelleri tamamlamış oluyor. Sessizlikten ödün verilmiyor." (Gorkem Yildirim, PCnet.com.tr)
02.06.2017 // mod-your-case.de
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NF-A4x20 PWM Review

Wir haben den Lüfter für unseren Test in einem 5,25" Festplattengehäuse verbaut, wo er einen der beiden werksseitig montierten Lüfter ersetzt. [...] Durch die OmniJoin-Adapter konnte der Lüfter im Handumdrehen angeschlossen und das Festplattengehäuse wieder zusammengesetzt werden. Gleich nach der Inbetriebnahme konnte man feststellen, dass der Geräuschpegel bei gleichbleibender Festplattentemperatur etwas gesunken war. Wird keine so hohe Kühlleistung benötigt, so kann man die Lüfterdrehzahl und somit auch die Geräuschkulisse über die mitgelieferten Low-Noise-Adapter senken.
Test verdict: "Durch die Bautiefe von 20 mm kann der Lüfter einen sehr guten statischen Druck sowie einen guten Luftdurchsatz erreichen" (Patrick Seus, mod-your-case.de)
02.06.2017 // Razorman.net
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NF-A4x20 PWM Review

Los nuevos ventiladores Noctua NF-A4X20 y Noctua NF-A12X15 ofrecen unas estupendas prestaciones como hemos podido comprobar generando en ambos casos un importante flujo de aire. Destacables son las prestaciones del modelo más pequeño aunque a costa de un ruido bastante superior.
Test verdict: "Los nuevos ventiladores Noctua NF-A4X20 y Noctua NF-A12X15 son la nueva apuesta de Noctua en diámetros de 12 y 4 cm, con unas excelentes prestaciones como es habitual en el fabricante Austríaco." (Ana Rey Carballeira, Razorman.net)

Installation Manual (PDF)

Information Sheet (PDF)

Can I disassemble my fan for cleaning (or other purposes, e.g. painting)?

In order to ensure flawless operation over many years of usage, all Noctua fans come with a premium grade SSO bearing, which is fully sealed to prevent the entering of fine dust particles. Please note that the fan is not designed to be taken apart by the user. Removing the impeller from the frame will break the sealing of the bearing and results in a loss of warranty.

It is thus recommended to clean your fans using a duster, slightly moist tissue or canned air. Please be careful not to use too much force in order to prevent any damage to the fan. Please don’t use a vacuum cleaner as this may apply excessive force to the fan.

Can I run 4-pin PWM fans on 3-pin fan headers?

PWM fans come with a 4-pin connectors for fully automatic speed control via your mainboard’s 4-pin PWM fan headers. Please note that 4-pin fans can also be connected to your mainboard’s 3-pin fan headers though. When connected to 3-pin fan headers, the fan will run at full speed (unless the mainboard supports voltage based speed control).

What pin configuration do Noctua 12V fans use?

All Noctua fans feature the standard pin-configurations set out in the Intel and AMD specifications. These standard pin-configurations are used on most mainboards and fan controllers today:

pin configuration

How should I clean my Noctua fan?

Fans inside computer cases tend to accumulate dust over longer periods of usage. In order to maintain maximum performance, please clean your fans regularly using a duster, slightly moist tissue or canned air. Please be careful not to use too much force in order to prevent any damage to the fan. Please do not use a vacuum cleaner as this may apply excessive force to the fan and do not put the fan under running water as water residues inside the motor may lead to short circuits.
In order to ensure flawless operation over many years of usage, Noctua’s premium grade SSO bearings are fully sealed to prevent the entering of fine dust particles. Please note that the fan is not designed to be taken apart by the user. Removing the impeller from the frame will break the sealing of the bearing and results in a loss of warranty.

Can I use Low-Noise Adaptors with y-cables / multiple fans?

Yes, Low-Noise Adaptors (L.N.A.s) can be used with y-cables, but please make sure to use one L.N.A. per fan and to place the L.N.A.s between the y-cable and the fans as shown below. Never use one L.N.A. for two (or more fans) by placing it between the mainboard and the y-cable!

D15S

How can I check if my 4-pin fan header supports PWM?

Some mainboards feature 4-pin fan headers that actually don‘t use a PWM signal on Pin 4 to control the fan speed but rather reduce the voltage on Pin 2 (like a standard 3-pin fan header). As the fan speed at minimum voltage is usually higher than the speed at 20% PWM duty cycle, the fan can not reach as low minimum speeds under voltage control as under PWM control. Please refer to your mainboard manual to check whether or not your mainboard has 4-pin fan headers that control the fan speed by reducing voltage on Pin 2 rather than by changing the PWM duty cycle on Pin 4:

4 pin fan header types

Note that mainboard manufacturers use different terms to indicate that Pin 4 is not being used for PWM control (e.g. “+5V”, “VCC” or “NC”), but if one of these terms is used, you can be sure that the fan header does not support PWM. If Pin 4 is described as “Speed Control” or “PWM” or the like, you can be sure that the fan header supports PWM.

Unfortunately, the description of Pin 2 is not always a clear indication as some manufacturers use terms such as “Fan PWR” or “Power” for both types of fan headers. However, if Pin 2 is described as “Speed Control”, you can also be sure that the fan header does not support PWM based speed control. If Pin 2 is described as “+12V”, this is a clear indication that the fan header supports PWM.

Please also note that in some cases, the descriptions of the pin layouts in the mainboard manuals may not be correct and some models actually allow you to switch the fan headers from voltage control mode to PWM control mode in the BIOS even though the pin descriptions do not indicate PWM support. We thus recommend to look for these options in the BIOS before taking other measures. In case of doubt, please contact your mainboard manufacturer.


If your mainboard features other 4-pin fan headers that use PWM for speed control, you can run multiple fans from these headers using Y-split cables. Make sure not to exceed the specified maximum power draw of the fan headers (usually 10-12W) though.

Can Noctua fans be used to replace noisy stock fans in NAS devices?

Noctua fans such as the 40, 60, 80 or 92mm NF-A series models are ideal for replacing noisy stock fans in NAS devices in order to make them quieter and thousands of users have managed to significantly reduce the noise levels of their NAS units this way. However, while it is easy and straightforward to replace the fans in some cases, it can be very difficult in others, so Noctua strongly recommends that users carefully research if it is possible to easily replace the fan(s) of their NAS device before purchasing a Noctua fan for this purpose. Some of the common issues that can occur when replacing NAS fans are:

  • Different pin assignment: Whereas Noctua fans use the standardised pin assignment for PC fans (see this FAQ for details), some NAS units use different assignments. For example, some devices have the power and GND or rpm and PWM pins swapped. Therefore please carefully verify that your NAS device uses the same pin assignment as standard fans. Experienced users may also change the pin assignment by cutting and resoldering the fan cables, but please note that this will void your Noctua manufacturer’s warranty.
  • Different pin functions: Noctua fans use the standardised pin functions for PC fans (see this FAQ for details); however, some NAS units use fans where certain pins serve a different function. For example, some devices use the RPM pin for “power good” signals. Therefore please carefully verify that your NAS device uses the same pin functions.
  • Firmware speed control: Some NAS devices demand a certain maximum or minimum fan speed. If the new fan doesn’t have the same or similar maximum or minimum speed, the device may display errors or even shut down.
  • Different starting voltage: Most NAS devices use voltage-based speed control. If the new fan has a higher starting voltage than the original fan, it may not start up right away. This may lead the NAS device to display errors or even shut down because it suspects a fan failure.
  • Different power draw: Some NAS devices monitor the fan’s power draw. If the new fan has a lower power consumption than the stock fan, the device might display errors or even shut down.

Please note that most NAS manufacturers don’t provide detailed documentation regarding fan compatibility and control, so users who want to replace the fans of their devices usually have to rely on “How to” guides, blog and forum posts or video tutorials. For example, there are excellent video tutorials available for changing the fans in popular Synology NAS models (DS416j, DS1515+ and DS1812+ in English, DS416/DS415/DS916/DS216/DS214 and DS1515+ in German). Please also note that fan compatibility and control can vary from model to model and even from revision to revision even if the devices stem from the same manufacturer. As a result, it is important to make sure that the information or guidelines you rely on when replacing your NAS fan are applicable to your specific model as well as your specific hardware and firmware revision.

Due to the possible issues listed above, Noctua recommends that only experienced users attempt to replace their NAS fans. Please note that since there are so many different NAS models and most of them lack documentation for aspects such as fan compatibility and control, Noctua customer support cannot assist you with compatibility issues when replacing NAS fans. Please contact your NAS manufacturer for any questions regarding aspects such as the device’s pin alignment or fan monitoring and control.

Can I use Noctua fans in my system from Acer, Apple, Dell, HP, Lenovo or other major brands?

Noctua 12V fans comply with the established specifications for standard PC systems issued by Intel and AMD. Systems from Acer, Apple, Dell, HP, Lenovo or other major brands often deviate from these specifications e.g. by using proprietary fan headers, custom pin-alignments or pin-configurations, different methods of fan speed control, etc. This can lead to compatibility issues when using Noctua fans in systems from said brands. Some of these problems can be avoided with some technical knowledge, but especially BIOS related issues (e.g. errors or shutdowns due to low fan speed) can often not be resolved. As a result, Noctua does not officially support systems from Acer, Apple, Dell, HP, Lenovo or other major brands.

Which Noctua fan or CPU cooler should I buy? How to choose the right model?

Not sure which Noctua product to buy? Our detailed buying guides for fans and CPU coolers help you to choose the model that works best for you.

Do you have a question concerning one of our products? Please use this form to pose a question!