How to read fan specs?

[adinuno]

Hi there,

 

I'm about to start venturing in a new build, but wanted to make sure I'm reading the fan specs properly before committing to buy them online. I've noticed most fans usually emphasize three main specs: Airflow, Air Pressure and Sound Level. There are many other specs, but these are what I assume is determining the how much this a given fan might be the right choice.

 

I understand some fans are optimized to deliver more Airflow (probably to be used as case fans) and others to deliver more Air Pressure (probably to be used for cooling CPUs), while Sound Level is kind of neutral.

 

My question is, I think I understand the values of Airflow (51.5 CFM, for example), but I don't understand the values of Air Pressure: can anyone help me understand if 3.52 mm H²O is better than 1.52 mm H²O, or am I looking at things the wrong way?

 

Thanks in advance!

[TrigrH]

2 minutes ago, adinuno said:

but these are what I assume is determining the how much this a given fan might be the right choice.

Longevity and blade design (air flow vs static pressure optimized designs) are more important than a spec sheet. Noctua or corsair mag lev fans run quiet and are built to last.

[adinuno]

21 minutes ago, TrigrH said:

Longevity and blade design (air flow vs static pressure optimized designs) are more important than a spec sheet. Noctua or corsair mag lev fans run quiet and are built to last.

I'm planning on getting some two 140mm to the front of the case and two 120mm (one top and another back), do you have any recommendations?

[NineEyeRon]

OK Fan basics

 

Blades

Far apart = air flow - best for exhaust or intakes without too much restriction (filters should be OK).

Close together = Pressure - best for radiators and heat sinks

NOTE: Some fans can be blanced between both, these are good when you have air filters.

 

Size

Bigger is of course better, 140mm fans tend to be quieter and move more air

Smaller fans fit in more spaces, 80mm fans are OK and often found on smaller heatsinks but can be a bit noisy.

 

Speed

PWM fans are good, these need a 4pin header on the motherboard and have greater control over their speed, downside is they are more expensive.

3pin fans are cheaper and very good when you know you don't want them to spin slower or have a variable RPM. If you just want it going at one speed all the time choose this type

 

Placement

So you need to decide if you want loud and cool or quiet and warm.

I recommend going for positive pressure, this means having more air coming in than being "sucked" out.

I like to think of my front fans as being the big air moving grunts of an aircooled setup (no radiators), often people put the radiators at the front which is good too if 240mm in lenght, not so good for 120mm length ones, they go at the back...

 

Work out how much air is coming in and going out. I like to have big PWM fans at the front which ran ramp up and blow in cooler air when needed. I work out the minumum this will likely be and buy the 3pin exhaust to keep under that value. 

 

Amps and Splitters

Most motherboard headers are 1 amp, you can find out the amps drawn by your fan on the hub. Mine draw less than 0.3 so I usually just stick to two fans per header, with medium/low RPM 120mm fans you could probably do 3 without issue. I have one header, the pump header, which is 2amp. I would have no issue putting a 3 way splitter on this, even for bigger fans.

 

Brands

Noctua rule the roost but they are EXPENSIVE! Their redux line is much more affordable but doesnt have all the "quiet tech". They are still good though. 

Most other brands are not bad.

 

Choosing a Fan

Work out if you want hot and quiet or loud and cool (best for OCing). In other words do you need a temperature ceiling or a noise one?

Look at the CFM, amps (to work out how many), the pin type and the RPM. Try and find the balance between CFM, dB (under 20 is very good) and price.

 

Best of luck!

 

[Victor Golf]

2 hours ago, adinuno said:

My question is, I think I understand the values of Airflow (51.5 CFM, for example), but I don't understand the values of Air Pressure: can anyone help me understand if 3.52 mm H²O is better than 1.52 mm H²O, or am I looking at things the wrong way?

 

I think I might be able to explain the how the pressure rating is measured for you.

 

There is a device called a manometer used to measure difference in pressure. Picture a long U shaped tube filled with water. That is a basic manometer. Now imagine you have a fan blowing into a box and one end of the U is connected to the box. The pressure that the fan can produce will displace some water in the tube and that measurement is where the 1.52 mm H²O comes from.

 

If doesn't make sense I'm sure someone can explain how a manometer works  better than me on YouTube or something. 

[WoodenMarker]

Airflow is how much air is moved without any restrictions. Static pressure measured in mmH2O refers to how high a column of water can be pushed by the pressure of the fan. Higher is better. dB or DBA refers to the intensity of sound and the scale is logarithmic and not linear. Basically, a rise in 10dB is a perceived doubling of loudness.

 

These specs are useful especially when there's nothing else to rely on but there's little to no regulation on how they're measured between manufacturers. Take these specs with a grain of salt and stick to benchmarks and in-depth reviews with standardized testing whenever possible. 

 

If you're interested in new fans and would like recommendations, list your specs, where you're shopping / located, budget, and what kind of features you're looking for. 

[adinuno]

4 hours ago, WoodenMarker said:

Airflow is how much air is moved without any restrictions. Static pressure measured in mmH2O refers to how high a column of water can be pushed by the pressure of the fan. Higher is better. dB or DBA refers to the intensity of sound and the scale is logarithmic and not linear. Basically, a rise in 10dB is a perceived doubling of loudness.

 

These specs are useful especially when there's nothing else to rely on but there's little to no regulation on how they're measured between manufacturers. Take these specs with a grain of salt and stick to benchmarks and in-depth reviews with standardized testing whenever possible. 

 

If you're interested in new fans and would like recommendations, list your specs, where you're shopping / located, budget, and what kind of features you're looking for. 

Thanks for the explanations

 

I'm looking at a budget of 60 to 70gbp to invest in my fans, buying in the UK.

 

I've already got two fans Fractal Design Dynamic X2 GP-12 120 mm, but I wanted to place them both on back and top and buy two 140mm to the front.

[WoodenMarker]

1 hour ago, adinuno said:

I'm looking at a budget of 60 to 70gbp to invest in my fans, buying in the UK.

I've already got two fans Fractal Design Dynamic X2 GP-12 120 mm, but I wanted to place them both on back and top and buy two 140mm to the front.

What case?

[adinuno]

7 minutes ago, WoodenMarker said:

What case?

Fractal Design Meshify C

[WoodenMarker]

1 hour ago, adinuno said:

Fractal Design Meshify C

NF-P14S are great and hard to go wrong with: https://pricespy.co.uk/computers-accessories/computer-components/cooling/fans/noctua-nf-p14s-redux-1500-pwm-140mm--p2659199

[adinuno]

50 minutes ago, WoodenMarker said:

NF-P14S are great and hard to go wrong with: https://pricespy.co.uk/computers-accessories/computer-components/cooling/fans/noctua-nf-p14s-redux-1500-pwm-140mm--p2659199

Thanks for the advice, that's great information!

 

By the way, how could I tell a fan is a static pressure fan or a high air flow fan? What kind of specs would I be looking for to be able to tell a difference?

[WoodenMarker]

7 hours ago, adinuno said:

Thanks for the advice, that's great information!

By the way, how could I tell a fan is a static pressure fan or a high air flow fan? What kind of specs would I be looking for to be able to tell a difference?

Fans that have relatively high static pressure or airflow are considered static pressure or airflow fans. Basically, it's fairly arbitrary and relative to the market.

If it isn't in the marketing material, you can generally see how steep the fan blades are. Fans with few, wide sweeping blades tend to be static pressure whereas fans with more fan blades tend to deliver more airflow. The appearances may be more reliable then the specs.

Example: NF-S12A - airflow (left), NF-F12 - static pressure (right)

Spoiler

 

The most appropriate fan is one that delivers as much airflow as possible while having enough static pressure for where its used. It isn't about just getting an airflow fan vs. static pressure when some fans are just better than others. 

When it comes to finding out what's most appropriate for your needs, look at fan reviews with tests that reflect your usage. The Meshify C has a fairly open mesh front so fans tested in open air or behind a light mesh would probably be comparable. Here's an example: https://www.overclockers.com/15-case-fans-tested-ultimate-140-mm-roundup/

 

NF-P14S was considered a static pressure fan but nowadays it's more of a balanced design since there's more of a focus on high static pressure. You didn't mention any particular features you're looking for so it's an easy recommendation considering the good performance / rpm range, low noise, great quality, and 5 yrs warranty / customer support. 

[adinuno]

19 hours ago, WoodenMarker said:

Fans that have relatively high static pressure or airflow are considered static pressure or airflow fans. Basically, it's fairly arbitrary and relative to the market.

If it isn't in the marketing material, you can generally see how steep the fan blades are. Fans with few, wide sweeping blades tend to be static pressure whereas fans with more fan blades tend to deliver more airflow. The appearances may be more reliable then the specs.

Example: NF-S12A - airflow (left), NF-F12 - static pressure (right)

  Hide contents

 

The most appropriate fan is one that delivers as much airflow as possible while having enough static pressure for where its used. It isn't about just getting an airflow fan vs. static pressure when some fans are just better than others. 

When it comes to finding out what's most appropriate for your needs, look at fan reviews with tests that reflect your usage. The Meshify C has a fairly open mesh front so fans tested in open air or behind a light mesh would probably be comparable. Here's an example: https://www.overclockers.com/15-case-fans-tested-ultimate-140-mm-roundup/

 

NF-P14S was considered a static pressure fan but nowadays it's more of a balanced design since there's more of a focus on high static pressure. You didn't mention any particular features you're looking for so it's an easy recommendation considering the good performance / rpm range, low noise, great quality, and 5 yrs warranty / customer support. 

Thanks, great stuff!

 

I've read the NF-A14 is an updated version of the P14, do you know anything about that?

[WoodenMarker]

4 hours ago, adinuno said:

I've read the NF-A14 is an updated version of the P14, do you know anything about that?

Yes, that's essentially what that is. If you don't mind spending more, the NF-A14 is slightly better. 

[adinuno]

2 hours ago, WoodenMarker said:

Yes, that's essentially what that is. If you don't mind spending more, the NF-A14 is slightly better. 

Hey! Thanks for all the help! I really appreciate