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PWM fan/connectors/air cpu cooler questions

System Specs: (I just ordered the compoments so I don't have them yet)
Case: Corsair Carbide 400C White
Motherboard: Asus Z270-A
CPU: Core i-5 7600k
GPU: Gigabyte GTX 1070
PSU: EVGA Supernova G3 750 PSU
CPU Air Cooler: Deepcool Assassin 2
Memory: 16GB (x2 8GB Stick) Corsair Vengence LPX
SSD: Kingston V300 240GB


Greetings TH community,

I haven't built a PC system for a long time, but I will be building one soon, and I have a few questions:

1. I understand PWM fans can be automatically controlled by the motherboard. The motherboard will adjust the speed accordingly in relation to the CPU and GPU temperatures.

1a. So to set these PWM fans to run in PWM mode, I have to go into the BIOS to set it. What I don't understand is, why there's multiple options for the fan speed when the motherboard is suppose control the PWM fans. Here is a screenshot:

http://imgur.com/a/2Mp1v (The screenshots aren't of my system)

2b. What does DC mode do? Is it for none PWM fans with 4 pin connectors?

3c. Now I read PWM fans are mainly for fan control. But none PWM fans can already be controlled from the BIOS, right? So what's he difference between PWM and none PWM fans if both fan types can be controlled?

4d. I've read that the only true PWM controlled 4 pin header on the motherboard is the CPU Fan header? The rest of the 4 pin headers on the motherboard are controlled in DC mode. I have no idea what this means. If someone could clear this up for me. So there's only one 4 pin header where you can actually run fans on PWM mode?


2. As you can see above, I purchased the Deepcool Assassin 2 CPU air cooler and I have a few questions:

2a. The two PWM CPU air fans connects to the PWM Deepcool fan hub. Then the Deepcool fan hub connects to the motherboard (In my case the Asus Prime-A). Where on my motherboard would I connect the Deepcool fan hub into? The CPU_FAN header? Here's a screenshot:

http://imgur.com/a/irIPg

2b. If you look at the screenshot below, it shows step 12, 13 and 14. I think 12 is showing the two PWM fans being connected to the hub. For step 13 it looks like the removal of a sticker or film from the rectangular piece? And for 14 I have no idea. Does anyone know?

2c. The Corsair Carbide 400C case only comes with x1 140mm front intake fan and x1 120mm back exhaust fan. I want to order x2 ARCTIC F14 PWM Rev.2 PWM fans. So I could connect these two PWM fans to the Deepcool fan hub? And these 2 Arctic fans would be controlled together with the 2 Deepcool PWM CPU fans?

2d. I read somewhere that connecting too many fans on the motherboard will put stress on the motherboard. Is this true? If so then should I connect the 2 extra Arctic PWM fans straight to the PSU?

2f. Where do I connect the 2 case fans that come with the The Corsair Carbide 400C case? Do I connect it to the PSU or to the board? What are the differences from the two? I can't figure out if the these two case fans are 3 or 4 pin. It doesn't say. Here is a screenshot:

http://imgur.com/a/juKbD

2g. If you connect a 4 pin fan to the PSU by connecting it to a molex 4 pin cable, can you control the fans from the BIOS? Or does it just run at full speed automatically without you having any control?

3. Last question. I just need to confirm that the two case fans in front will be intake fans (suck in cool air), and the one fan I'll put on top and one on the back are exhaust fans (suck out hot air). Because in this video, the guy says the top fans are sucking in air into the case. So that video kind of confused me. Just need to make sure I was right. Here is the video:
https://www.youtube.com/watch?v=MUFOvLEX1Sc


That's all the questions I have for now. It's a lot of questions and I hope I'll be able to find answers here. Thank you all!
5 answers Last reply Best Answer
More about pwm fan connectors air cpu cooler questions
  1. Hi. Let me try to answer your questions:
    Crom808 said:
    1. I understand PWM fans can be automatically controlled by the motherboard. The motherboard will adjust the speed accordingly in relation to the CPU and GPU temperatures.

    1a. So to set these PWM fans to run in PWM mode, I have to go into the BIOS to set it. What I don't understand is, why there's multiple options for the fan speed when the motherboard is suppose control the PWM fans. Here is a screenshot:

    http://imgur.com/a/2Mp1v (The screenshots aren't of my system)

    2b. What does DC mode do? Is it for none PWM fans with 4 pin connectors?

    3c. Now I read PWM fans are mainly for fan control. But none PWM fans can already be controlled from the BIOS, right? So what's he difference between PWM and none PWM fans if both fan types can be controlled?


    Older motherboards have 4-pin and 3-pin headers, in which, you can easily determine visually which one is PWM (4-pin) and which one is non-PWM (3-pin). The non-PWM header (3-pin) lacks the 4th pin used for PWM control signal.

    Some older and some newer motherboards have all its fan headers with 4 pins - but not all of these headers work electronically the same way - as some are PWM and some are non-PWM. You would have to consult the manual to find out how these 4-pin headers function. 4-pin non-PWM headers have its 4th pin as a "dummy pin" (i.e., no electronic connection).

    Most new motherboards today have all its fan headers with 4 pins and with feature to change such 4 pins either in PWM or DC (non-PWM) mode via BIOS -- like the photo link you posted above. Such fan headers are default set in PWM or DC mode out-of-the-box but you can easily configure it whichever mode you like. In the photo, the standard, silent, turbo, and full speed options are just pre-determined curves of the graph to indicate what speed the fan will run on a given temperature. You can set this manually.

    Both PWM fans and non-PWM fans can be controlled by the motherboard, if the fan headers of such motherboard have these control features in BIOS. PWM mode has its 2nd pin providing constant +12VDC and, as mentioned above, its 4th pin using PWM signal for variable current communicating with the PWM fan chip to change the fan's speed. On the other hand, DC mode has its 2nd pin providing variable DC voltage (used to change the fan's speed) and, as mentioned above, its 4th pin not electronically connected (dummy pin).

    Since both types of fan headers can be controlled in newer motherboards (such as yours), typically, you want to match the fan type with the fan control header mode of the mobo's BIOS. That is, PWM fans = PWM mode; DC fans = DC mode.

    Plugging a non-PWM fan on a PWM header will result in the fan running at full speed 24/7 due to the constant +12VDC the 2nd pin provides, i.e., you cannot change the fan's speed. Plugging a PWM fan on a DC header will result in the fan able to change it's speed but through lowering its voltage but the fan is not functioning as a true PWM fan.

    Crom808 said:
    4d. I've read that the only true PWM controlled 4 pin header on the motherboard is the CPU Fan header? The rest of the 4 pin headers on the motherboard are controlled in DC mode. I have no idea what this means. If someone could clear this up for me. So there's only one 4 pin header where you can actually run fans on PWM mode?


    That was the case on older (and some new) motherboards (see what I have discussed above).

    In the motherboard you ordered, the Asus Z270-A, all of its 6x total fan headers (CPU_FAN, CPU_OPT, CHA_FAN1, CHA_FAN2, AIO_PUMP, and H_AMP) are all 4-pins. All of these fan headers can be changed to work with 4-pin PWM fans and 3-pin non-PWM fans by selecting the appropriate PWM or DC mode as mentioned above.

    Crom808 said:
    2. As you can see above, I purchased the Deepcool Assassin 2 CPU air cooler and I have a few questions:

    2a. The two PWM CPU air fans connects to the PWM Deepcool fan hub. Then the Deepcool fan hub connects to the motherboard (In my case the Asus Prime-A). Where on my motherboard would I connect the Deepcool fan hub into? The CPU_FAN header? Here's a screenshot:

    http://imgur.com/a/irIPg

    2b. If you look at the screenshot below, it shows step 12, 13 and 14. I think 12 is showing the two PWM fans being connected to the hub. For step 13 it looks like the removal of a sticker or film from the rectangular piece? And for 14 I have no idea. Does anyone know?


    There are several ways to connect the Deepcool Assassin 2. First is using the Deepcool fan hub as shown in your posted pic. The two CPU cooler fans connect to the hub, then the hub should be connected to the CPU_FAN header (recommended). You can also plug in the hub in a different header (in PWM mode) but make sure you plug something (another fan) on that CPU_FAN header to avoid any error message warning.

    Since your motherboard has an abundant supply of fan headers, you can also eliminate the use of the Deepcool fan hub (it's only optional). The fan hub is ideal if you have very limited fan headers or if you just want to save on fan headers for future fan connection/expansion. Since the Asus Z270-A has a CPU_FAN and a CPU_OPT (labelled #3 in the photo link you posted), you can also, optionally, plug one CPU cooler fan on the CPU_FAN and plug the other CPU cooler fan on the CPU_OPT (both headers using PWM-mode).

    The above options will function the same way - using PWM signal to control the speed of your CPU cooler's PWM fans based on temperature.

    Step 14 just shows an option for mounting the Deepcool fan hub via Zip ties (instead of the 3M sticker in Step 13). The fan hub has a "hole" in the frame body where you can insert the Zip tie to securely fasten the hub in case you don't want to use stickers in your chassis for easier removal later on.

    Crom808 said:
    2c. The Corsair Carbide 400C case only comes with x1 140mm front intake fan and x1 120mm back exhaust fan. I want to order x2 ARCTIC F14 PWM Rev.2 PWM fans. So I could connect these two PWM fans to the Deepcool fan hub? And these 2 Arctic fans would be controlled together with the 2 Deepcool PWM CPU fans?

    2d. I read somewhere that connecting too many fans on the motherboard will put stress on the motherboard. Is this true? If so then should I connect the 2 extra Arctic PWM fans straight to the PSU?


    Most motherboards have its fan headers rated at max. 1A, unless otherwise specified. There are some specific headers that can accommodate a higher ampere draw (2A or 3A), such as your Asus Z270-A's H_AMP header (which stands for "high ampere" header).

    In connecting several fans running off of one header, you need to check the total ampere draw of all the fans you will use (this is easily seen in the sticker label at the back of the fan or the box or the spec sheet). So, let's say your Arctic F14 PWM draws 0.3A each. Using two of these will total 0.6A - which is still way below the 1A max. on typical motherboard fan headers -- you'll be safe. However, plugging another 0.3A fan will total to 0.9A -- a bit close to the max and not recommended. You can use a lower amp fan though (like 0.15A) to add to your 0.6A total. So, the point is, compute the total amount of draw so as not to reach the limit.

    If you have high amp draw fans, you can safely use the H_AMP header in your motherboard to connect all those fans (after computing the total draw) via a fan hub. You can set the mode in PWM if you are using PWM fans.

    Alternatively, connecting such fans to the PSU (via a 4-pin to molex cable) is also doable. However, you'll be running the fans at full speed 24/7 and lose the fans' PWM function if they are PWM fans.

    Crom808 said:
    2f. Where do I connect the 2 case fans that come with the The Corsair Carbide 400C case? Do I connect it to the PSU or to the board? What are the differences from the two? I can't figure out if the these two case fans are 3 or 4 pin. It doesn't say. Here is a screenshot:

    http://imgur.com/a/juKbD


    The Corsair AF140L and AF120L case fans are both low-speed 3-pin DC fans. The AF140L is 140mm in size, while the AF120L is 120mm in size.

    Crom808 said:
    2g. If you connect a 4 pin fan to the PSU by connecting it to a molex 4 pin cable, can you control the fans from the BIOS? Or does it just run at full speed automatically without you having any control?


    No you can't. It will run full speed 100% 24/7 without any control (similar to connecting a 3-pin DC fan in a 4-pin header in PWM-mode, as I mentioned above).

    Crom808 said:
    3. Last question. I just need to confirm that the two case fans in front will be intake fans (suck in cool air), and the one fan I'll put on top and one on the back are exhaust fans (suck out hot air). Because in this video, the guy says the top fans are sucking in air into the case. So that video kind of confused me. Just need to make sure I was right. Here is the video:
    https://www.youtube.com/watch?v=MUFOvLEX1Sc


    That's the logical airflow:
    Front (and Bottom, if any) = Intake
    Rear (and Top, if any) = Exhaust

    But, it's all a matter of preference really and a case-to-case basis. It's not a pre-determined orientation and you can choose which direction you mount your fans if it will help lower the particular temperature in your chassis.
  2. Thanks so much for ready all my questions raisonjohn. You're awesome man. I appreciate it! I have a couple more questions for you or anyone reading:

    1. My Corsair Carbide 400C case came in today. And I checked the fan pin connectors for the 120mm and 140mm fans that came with it and they are both 3 pins (Just 3 pins, not 4 pin with the 4th pin being a dummy pin). So since all of the fan headers on my board are 4 pins, where do I connect these 3 pin fans? They can't fit in the 4 pin headers can they? And if they do, how do I connect it to a 4 pin? And which header rod do I exclude? Here is the screenshot of my motherboard again just incase you need a reference:


    http://imgur.com/a/irIPg

    2. How would you setup my fans? If you can go in detail on which fan to connect to which header and whether I should include or exclude the PWM fan hub that came with the Deepcool Assassin 2 CPU cooler.

    - x2 Deepcool Assassin 2 CPU cooler fans (Cooler kid included a PWM fan hub with 4 slots
    - x2 140mm PWM Arctic fans (I plan on putting these two fans in the front)
    - x1 Corsair 120mm fan for the back (Non PWM and only 3 pin. Came with the case)
    - x1 Corsair 140mm for the top (Non PWM and only 3 pin. Came with the case)

    Thanks again for the help!
  3. Best answer
    You're very welcome! As to your follow-up questions:

    Crom808 said:
    1. My Corsair Carbide 400C case came in today. And I checked the fan pin connectors for the 120mm and 140mm fans that came with it and they are both 3 pins (Just 3 pins, not 4 pin with the 4th pin being a dummy pin). So since all of the fan headers on my board are 4 pins, where do I connect these 3 pin fans? They can't fit in the 4 pin headers can they? And if they do, how do I connect it to a 4 pin? And which header rod do I exclude? Here is the screenshot of my motherboard again just incase you need a reference:

    http://imgur.com/a/irIPg


    The included 3-pin case fans that came with your 400C can be plugged into 4-pin motherboard fan headers like this:

    Notice the small tab encompassing pins 1, 2, and 3. Just align the groove of that 3-pin socket and it will fit nicely, leaving the 4th pin freestanding/unplugged.

    As I have mentioned in my previous reply, your case fans, being a 3-pin fan, are DC (or non-PWM) fans. Plugging DC fans on a 4-pin header in PWM-mode will result in your fans spinning 100% full speed 24/7 due to the 2nd pin of your motherboard's header providing constant +12V DC to your fans.

    Your Asus Z270-A motherboard should have an option to change the 4-pin header's mode from PWM-mode to DC-mode (this is done in the BIOS). It should look like this:

    This way, your 4-pin motherboard headers will act as a "3-pin header" by providing variable voltage at the 2nd pin and the 4th pin will have no electronic connection (since it won't be plugged anyway). You can now change the speed of your DC case fans by creating a fan curve (or clicking on pre-set modes such as "silent", "full speed", etc.) if you prefer.

    Otherwise, if you have no qualms on running your case fans at full speed (noise doesn't bother you), then, you can leave the settings as is (i.e., just plug the 3-pin fan on a 4-pin PWM header). Note that your motherboard may also "Auto-Detect" what type of fan you have connected, so, check your BIOS if it has changed to DC or not.

    Crom808 said:
    2. How would you setup my fans? If you can go in detail on which fan to connect to which header and whether I should include or exclude the PWM fan hub that came with the Deepcool Assassin 2 CPU cooler.

    - x2 Deepcool Assassin 2 CPU cooler fans (Cooler kid included a PWM fan hub with 4 slots
    - x2 140mm PWM Arctic fans (I plan on putting these two fans in the front)
    - x1 Corsair 120mm fan for the back (Non PWM and only 3 pin. Came with the case)
    - x1 Corsair 140mm for the top (Non PWM and only 3 pin. Came with the case)


    There are no hard-and-fast rules in setting up and connecting your fans. Everything is a matter of preference. The only important fan and fan header to be connected is the CPU_FAN header and your CPU Cooler Fan/s.

    Your Asus Z270-A motherboard has a total of 6x fan headers (i.e., CPU_FAN, CPU_OPT, CHA_FAN1, CHA_FAN2, H_AMP_FAN, and AIO_PUMP). All of these headers are 4-pin headers and can be changed to either PWM or DC mode in BIOS.

    In typical Asus motherboards, the CPU_FAN, CPU_OPT, CHA_FAN1 and CHA_FAN2 are typically rated at 1A each and, by default, set in Variable Speeds. The H_AMP_FAN is typically rated at 3A (H_AMP = high_ampere) and, by default, set in Full Speed. The AIO_PUMP, typically rated at max. 1A, by default, is set in Full Speed.

    *******Additional info (you may skip this, or read on)*******
    In a typical build, 1 fan is connected to 1 fan header (you can use any header of your motherboard as you please). But in cases where the total number of headers in your motherboard is not enough for the number of fans you are installing, you have the option to plug in several fans off of 1 fan header, which is done via splitters or fan hubs.

    The importance of the ampere rating (1A or 3A) is to know the limit of the number of fans you can connect in that header. You would then need to check the ampere draw of your fan (this can be seen at the back of the fan with the sticker label, or the box specs). For safety, you want to use only 75% of the 1A max. rating of the header. So, for example, you have 3 case fans all rated at 0.3A each. You can safely plug 2 of those (total of 0.6A), but not recommended to plug all 3 (total of 0.9A).
    *************************************************

    As you have listed above, you would be connecting a grand total of 6x fans. Since your motherboard has 6x fan headers, you are all set (so no need to use splitters or fan hubs connecting several fans in one header as I have described above). Personally, I would rig up your fans like this:

    CPU_FAN --> PWM-mode --> 1x Deepcool Assassin II CPU cooler fan (4-pin)
    CPU_OPT --> PWM-mode --> 1x Deepcool Assassin II CPU cooler fan (4-pin)
    CHA_FAN1 (near top right corner) --> PWM-mode --> 1x 140mm Arctic PWM fan at front intake (4-pin)
    CHA_FAN2 (bottom right corner) --> PWM-mode --> 1x 140mm Arctic PwM fan at front intake (4-pin)
    H_AMP_FAN (near rear exhaust) --> DC-mode --> 1x 140mm Corsair fan at top exhaust (3-pin)
    AIO_PUMP (near rear exhaust) --> DC-mode --> 1x 120mm Corsair fan at rear exhaust (3-pin)

    The above setup would not use the included "fan hub" (which is just a splitter). It's up to you to use it or not. Using the fan hub would create an available header for you should you add another fan in the future (as you have used up all 6x fan headers with your 6x fans in the above setup).
  4. raisonjohn's advice and info above is excellent. Follow it.

    Just FYI about your question 1a on multiple options. The "normal" way to set the options for EACH fan port is to use the "Standard" mode. This uses a pre-set group of settings for fan speed versus actual measure temperature that is very well suited to most needs. But some people prefer to change from that, so others are offered here. "Silent" forces the fan to run slower than normal, which MAY mean your system is running hotter that "ideal", and certainly will mean it will never use the fan's full speed and cooling ability. "Turbo" is the opposite - the fan runs faster than normal, making more noise and providing cooler operation than "Standard". "Full Speeds" means the fan is NOT under any automatic control based on temperature, it just runs full speed all the time. "Manual" allows you to take the bending points on the graph above and change them interactively to set your own custom version of what the automatic system will do for this fan.

    Note that EACH fan header can be configured separately. If you want to make changes, do changes for every fan header - what you do on one will NOT be automatically applied to any others.

    The manual says the mobo actually contains more than one temperature sensor that can be used to guide automatic temperature-based control of fan speeds, but does not show how to choose those.

    Background: every automatic fan speed control system is really a TEMPERATURE control system. That is, the AIM of each is to control the TEMPERATURE as measured by a sensor. The system manipulates the speed of a fan to do this. On most mobos there are two separate such control systems. The CPU_FAN header always is based on a temperature sensor built into the CPU chip itself and available to the mobo as a signal on one of the chip's pins. Normally any CPU_OPT header also is based solely on this sensor. Most mobos apply extra monitoring of the performance of the actual CPU cooler to ensure the CPU chip can never overheat and be damaged, BUT they do this in part by checking the speed signal of the fan plugged into the CPU_FAN header. So it is IMPORTANT that the actual CPU cooling fan be plugged into the CPU_FAN header.

    The second "normal" control system is used for the CHA_FAN headers and uses a sensor built into the mobo. This normally is used for case ventilation fans. Your mobo has two of those headers, plus some others. It also has much more flexibility than many mobos. The result is that you can make separate configuration choices for each fan header to customize what their fans do. For each you can choose which temperature sensor is used (and how/where? is what I cannot find in the manual), whether it uses PWM Mode (for 4-pin fans) or DC Mode (for 3-pin fans) as a control method, and the fan Profile (i.e., which of those several options for speed versus temperature). For all your case fans I suggest you start with using the Motherboard temperature sensor, the "Standard" profile, and set the control Mode to PWM or DC according to the fan type you plug into that header. IF you choose to use a splitter to connect two or more fans to one header, be sure to connect together ONLY fans of the same type (3-pin together, and 4-pin together) and set their header accordingly.

    In my view, the Deepcool "Fan Hub" included with that cooler system is really a Splitter, but it will do what you need very well. Picky of me, maybe. I use the term "Splitter" to label a device that simply connects two or more fans in parallel to a single header and thus provides power and control of all its fans solely from that header. This works just fine if the total fan load on the header is less than 1 amp for most headers, and that is what your Deepcool Assassin II system will do nicely for your CPU_FAN header. To me, a "Hub" is a different device that gets power for its fans directly from the PSU using a separate connection cable, and thus avoids the 1 amp limit of a normal header. Such devices normally can work only with true 4-pin headers that use PWM Mode, and with 4-pin fans only. But you have so many mobo fan headers, each with very flexible configuration options, that you don't need such a device.
  5. Thanks again @raisonjohn @Paperdoc for the help. Very helpful information!
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