Featuring advanced aerodynamic design measures such as Flow Acceleration Channels and an AAO frame, the NF-A4x20 5V PWM is a PWM enabled 5V variant of Noctua’s highly optimised, premium quality quiet 40x20mm fan. The custom designed NE-FD3 PWM IC that integrates Smooth Commutation Drive technology and Noctua’s reference class SSO2 bearings guarantee superb running smoothness and excellent long-term stability. Topped off with modular cabling, the OmniJoin™ Adaptor Set and 6 years manufacturer’s warranty, the NF-A4x20 5V PWM is a premium choice for demanding 5V applications that require PWM control.
Being a 5V fan, the NF-A4x20 5V PWM cannot be run at 12V and will be damaged when used with typical 12V power sources such as PC motherboard fan headers.
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.
5V PWM version

5V PWM version

Many devices such as network or storage solutions use 5 volt 40mm fans with PWM speed control. With the same operating voltage, PWM support and the included OmniJoin™ adaptor set that makes it compatible with proprietary fan headers, the NF-A4x20 5V PWM is ideal for replacing noisy or broken 5V 40mm fans with PWM.
Polarity protection

Polarity protection

As many devices using 5V fans feature proprietary connectors and documentation of the pin alignment may not be available, the fan features an integrated diode for polarity protection. This way, you're on the safe side if you accidentally connect it with reverse polarity.
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.
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-FD3 5V 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.
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.
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.
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 5V PWM
Notes and warnings
Being a 5V fan, the NF-A4x20 5V PWM cannot be run at 12V and will be damaged when used with typical 12V power sources such as PC motherboard fan headers.
FAN Specification
40x40x20 mm
Mounting hole spacing
32x32 mm
4-Pin PWM
Blade Geometry
Rotational Speed (+/- 10%)
5000 RPM
Min. Rotational Speed (PWM, +/-20%)
1100 RPM
Acoustical Noise
14,9 dB(A)
Static Pressure
2,26 mm H₂O
Max. Input Power
0,5 W
Max. Input Current
0,1 A
5 V
> 150.000 h
Scope of Delivery
  • 4-pin y-cable
  • 30cm extension cable
  • OmniJoin™ adaptor set
  • NA-AV3 anti-vibration mounts
  • Fan screws
6 years
NF-A4x20 5V 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.
17.08.2017 // APHNetworks.com

NF-A4x20 5V PWM Review

Noctua is well known for being quiet, but also have good performance. They have definitely stayed true to their reputation. The Noctua NF-A series have exceptional build quality through and through. All of the fans performed well during the tests. On top of that, they were also quiet, especially if run at nominal speeds instead of their maximum.
Test verdict: "The Noctua NF-A Series is a comprehensive line up of fans that will be great addition to many system environments." (Ben Joubert, APHNetworks.com)
10.08.2017 // WhatNext.pl

NF-A4x20 5V PWM Review

Wszystkie wentylatory oraz akcesoria są godne polecenia. Noctua ponownie pokazuje, że umie zrobić świetne konstrukcje. Śmigła są wydajne i prezentują się dobrze pod względem kultury pracy. Także jakość wykonania stoi na najwyższym poziomie. Podobnie jest z akcesoriami – świetne wykonanie i odpowiednie działanie.
Test verdict: "W zakupie sprzętu przeszkadzać może jedynie cena, która jest spora. Jednakże znakomite produkty nie mogą być tanie bo było by zbyt pięknie." (Michał Andruszkiewicz, WhatNext.pl)
12.07.2017 // FunkyKit.com

NF-A4x20 5V PWM Review

We have no doubt about the top quality of Noctua products. Each one of them is well designed. Even the package is exceptional. Most manufacturers are missing these little things that count while Noctua provides package with everything you may need for installation. Long years of designing and engeneering gave great results. Where you could think there can’t be done much more, Noctua proved that even the best products can be improved. New A series fans are the best in their class and it’s hard to find anything similar on the market. Even though new fans are considered as “slim”, they provide top air pressure while keeping low level of generated noise. Perfect balance for all who expect the best from their fans.
Test verdict: "We are recommending all new Noctua products without any hesitation!" (Bartosz Waluk, FunkyKit.com)
10.07.2017 // PC Ekspert

NF-A4x20 5V PWM Review

Veliki NF-A20 i u PWM i U FLX verziji košta oko 33 € što je korektna cijena za veličinu ventilatora, svu opremu koju donosi i na kraju krajeva vrlo dobre performanse uz ne previsoku buku. Kvaliteta izrade je visoka, materijali odlični a tehnologije jamče dugovječnost – kao i šest godišnje jamstvo uostalom. NF-A12x15 su po cijeni od 24 € pogodni za ugradnju u skučenija HTPC kućišta i na manje hladnjake, a obavezno ih se treba malo usporiti jer su na visokim okretajima čujniji. “Propuh” koji stvaraju je vrlo dobar i na nižim okretajima. A4x20 je u svim verzijama oko 20 €. Visoka je to cijena za 40-milimetarske ventilatore, no zbog kvalitete izrade, jamstva i ponajprije velike kompatibilnosti i mogućnosti prilagodbe isplati se platiti i tako visoki iznos. Ventilatori jesu bučniji pri visokim okretajima, no za kakav komad mrežne opreme koji je u ormaru to i nije bitno, a koncentrirana je zračna struja visoka i moćna. NA-SAV3 i SAV4 su po 11.50 € za što kupac dobiva kvalitetu, kompatibilnost s velikim brojem ventilatora i 16 komada nosača za po četiri ventilatora. NA-FC1 je svestran i kvalitetan kontroler za do tri ventilatora koji je moguće napajati direktno iz SATA Power konektora, pa može kontrolirati i jače ventilatore, no nije jeftin – 15 €. I za kraj, NA-SAC5 adapter koji može biti iznimno koristan za jače ventilatore koji se direktno napajaju iz SATA Power konektora i tako ne opterećuju ploču. Negativna je jedino cijena od oko 8 €.
Test verdict: "Noctua koristi svoju veliku ekspertizu u izradi sve boljih ventilatora iz godine u godinu. Novosti za ovu su tri varijante koje smo u ovom članku pokazali i svaka je od njih posebna, a to uključuje i sve izvedenice pojedinih ventilatora. [...] Svi Noctuini proizvodi su kao uvijek korisni i zaslužuju visoke preporuke, a jedino što ima zapravo možemo zamjeriti je nešto viša cijena za naše hrvatske (prazne) džepove." (Krešimir Matanović, PC Ekspert)
02.07.2017 // Freeocen.de

NF-A4x20 5V PWM Review

Das äußerst umfangreiche und hochqualitative Angebot von Noctua lässt jedes Herz höherschlagen. Durch die Anforderungen auf industrieller Ebene kann der Benutzer immer sicher sein, ein sehr ausgereiftes und langlebiges Produkt zu besitzen. Das bestätigen unsere Tests und auch die Anwendungsvielfalt.
Test verdict: "Die Resonanz der Kunden lässt keine Zweifel daran, dass auch die A-Serie wieder ein voller Erfolg ist." (Louis Spieckerhoff, Freeocen.de)
30.06.2017 // OCClub.ru

NF-A4x20 5V PWM Review

Рассмотренные новинки Noctua – это то, чего многие ждали. Можно сказать это “празднество размеров”. Конечно, это не мейстрим-модели, и врядли получат широкое распространение, но они рынку были очень нужны. Да этого момента на рынке не было качественных 200 мм моделей вентиляторов, не было тонких 120 мм моделей. Новые Noctua A-серии – модели фактически уникальные, и их, по сути, даже сравнивать не с чем. Нет в этой нише конкурентов. Пока. Тестирование вентиляторов – дело совсем неблагодарное, и крайне требовательное оснастке. Особенно все это важно при рассмотрении вентиляторов, у которых заявленный уровень шума 24 дБА и ниже. При столь низком уровне шума шумометр работает плохо. Просто не улавливает разницы. Именно поэтому данный материал скорее не полноценный обзор, а ознакомление.
Test verdict: "Главное достоинство вентиляторов Noctua A-серии – уникальные размеры. За это можно простить все. Хотя и прощать то здесь нечего. Раздел “минусы” на этот раз пустой. Здесь все классно." (Oleg Ubeiko, OCClub.ru)
28.06.2017 // GreenTechReviews.ru

NF-A4x20 5V PWM Review

Новый 40 мм вентилятор Noctua под именем NF-A4x20 5V PWM является отличным эволюционным развитием NF-A4x10 5V PWM – благодаря улучшенным фирменным технологиям, при возросшей скорости вращения уровень шума удалось снизить, увеличив, при этом, воздушный поток и, соответственно, эффективность вентилятора в целом. Нельзя не отметить и богатый комплект поставки (в частности – адаптеры OmniJoin), который значительно расширяет возможности установки вентилятора в различные устройства.
Test verdict: "Вентиляторы Noctua NF-A4x20 на данный момент являются самыми качественными решениями на рынке среди всех 40 мм вентиляторов!" Владимир Солонин, GreenTechReviews.ru)
17.06.2017 // XtremeSystems.org

NF-A4x20 5V 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

NF-A4x20 5V 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)
14.06.2017 // mod-your-case.de

NF-A4x20 5V PWM Review

Mit dem NF-A4x20 5V PWM hat Noctua seine A-Serie um einen weiteren 40 mm großen 5V-Lüfter erweitert, dessen Einsatzgebiet auf den ersten Blick erst einmal recht speziell ist. Schaut man sich jedoch in einem gut ausgestatteten Haushalt seine Hardwarekomponenten etwas genauer an, so kann man dort schnell einmal auf ein Gerät stoßen, in dem ein 40-mm-Lüfter arbeitet, der nur mit 5V betrieben wird. Genau an dieser Stelle ist das Einsatzgebiet des neuen NF-A4x20 5V PWM zu finden, wobei es hier noch nicht so viele Geräte gibt, welche die verbauten Lüfter mittels eines PWM-Signals steuern. Der Lüfter kann hier nicht nur als Ersatz für einen defekten Lüfter dienen, sondern auch dafür sorgen, das Geräuschlevel der entsprechenden Komponente zu senken. Durch die Bautiefe von 20 mm kann der Lüfter zudem einen sehr guten Luftdurchsatz erreichen, ist hierdurch jedoch auch nicht zu jedem Gerät, in dem ein 40 mm großer 5V-Lüfter zum Einsatz kommt, kompatibel.
Test verdict: "Die Verarbeitung des Lüfters ist auf einem sehr hohen Niveau, welches sich auch in der MTBF von 150.000 Stunden und der Garantiezeit von sechs Jahren widerspiegelt. Die UVP liegt bei knapp 15€, womit der Lüfter nicht gerade günstig. Die eigenen Nerven werden es einem jedoch recht schnell danken, wenn z.B. die quirligen Lüftergeräusche aus dem heimischen NAS gemindert werden." (Patrick Seus, mod-your-case.de)

Installation Manual (PDF)

Information Sheet (PDF)

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

What pin configuration do Noctua 5V fans use?

The pin configuration of Noctua 5V fans is identical to 12V fans:

5v 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 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).

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 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.

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 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!


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!