Is fan spitters safe?

[olekristianrudjord]

Hi, i just my very first gaming pc about a month ago. It is done, but i am not too happy with the thermals or the noise levels. I am using the Fractal Design Meshify C with two 140 mm fans as intake, two 120 mm fans as top exhaust (set to a lower rpm) and a 120 back exhaust with my Corsair H60 (2018).

I consider going 1x120mm fan at the botton of the case, 3x120mm fans for front intake, 2x120mm fans for top exhaust and 1x120 for rear exhaust. But there is one problem, i do not have more than 4 fan headers on my motherboard and 1 cpu fan header (5 in total). I need two more headers, would it be possible to use a cheap fan spitter for two of my intake fans and one splitter for the top exhaust? i have read that fan splitters are unsafe for your motherboard and fans, but i will not set them to their max speed (maybe 1000rpm or so).

Is this safe? and if so, should i just buy some from ebay for like 1-2$?
also, will i still be able to use pwm control on the fans conected to the splitters.

 

[Dark Lord of Tech]

Thermals won't change much with the new fan configuration, the low end H60 isn't a very good cooler.

 

[Paperdoc]

To be completely sure of the answers, we need more info. Specifically, maker and model numbers for all your fans and your mobo. Why?

The central issue is that 3-pin fans and 4-pin fans should not be mixed if possible, because each of those requires a different speed control method, and a single mobo header can only do one method. Now, with several headers, you can get around that because most mobo headers today can be set to use either method - you just have to match header Mode to fan type. Whether YOUR mobo can do this is why we need its specs.

Next, you need to distinguish between a Splitter and a Hub. A Splitter is a simpler device. It has ONE input arm with a female (with holes) connector on its end, and two or more output arms with male (pins) connectors into which you can plug your fans. It has NO other types of arms. It simply connects all of its fans to the header in parallel, and thus the header is the ONLY source of power for all the fans on that Splitter. Most mobo headers can supply up to 1.0 A max current to the total of all fans connected to that header, and that is the limit you must use. Splitters used to have a "bad rap" because people tried to connect too many fans (and hence too much current draw) to a single header, AND older fans often used more current than modern designs. Today the common case fans pull 0.1 to 0.2A each, so even four fans is well within the capability of a single header. The exception to that "rule of thumb" is LED fans (not the newer RGB fans with two cables from them). The LED fans that came out first have only one power cable to them and it feeds both the motor and the LED's, and that causes them to pull 0.3 to 0.5 A each.

A fan HUB is a different device. It has a third type or "arm" that ends in a Molex male or a SATA power connector, and that must be plugged into a power output from a PSU. The Hub gets power for all its fans from that PSU source and hence avoids the 1.0 A limit of the header. It draws no power from the header, but it does distribute the PWM signal from Pin #4 of the header to all its fans; this does NOT overload that signal source. But this means that the HUB depends entirely on its fans to use their PWM Mode capabilities - that is ALL its fans MUST be of the 4-pin type - AND that it can be used ONLY with a mobo 4-pin header that actually IS using the PWM Mode of control. I find that many sellers mislabel their devices as Splitters or Hubs when they are not. That's why I have described now to tell them apart.

The speed of a 3-pin fan can be controlled ONLY by changing the voltage supplied to it on Pin #2, which is called Voltage Control Mode or DC Mode. Since HUBS do NOT do things this way, you cannot use them with 3-pin fans. (There is one special Hub that is an exception to that "rule".) Thus if you are using 3-pin fans you really should be using a SPLITTER to connect more than one to a header.

The speed of 4-pin fans is best controlled by the new PWM Mode, although it CAN be controlled also by the older Voltage Control Mode.

The connection systems for 3- and 4-pin fans are very similar so you can always connect either fan type to either 3- or 4-pin headers and cable connectors. Among other things, this means that, when choosing a SPLITTER, it does not matter which type you get. Both types of Splitter will work correctly with both types of fans. BUT what is important is matching the fan type to the Mode that the HEADER is using to accomplish speed control.

OP, one item in your post struck me. You say you are not satisfied with the cooling performance you are getting, but ALSO say that you have deliberately slowed down some fans, presumably for noise reduction. Slower fans produce less cooling! If you want more cooling, first try letting all your fans run under automatic control so they DO produce the cooling required. THEN if you still need more cooling, consider whether more fans is the right way to go. OR, if you like the cooling but not the noise, consider replacing your fans with different models that will produce less noise for the SAME air flow.

 

[olekristianrudjord]

To be completely sure of the answers, we need more info. Specifically, maker and model numbers for all your fans and your mobo. Why?

The central issue is that 3-pin fans and 4-pin fans should not be mixed if possible, because each of those requires a different speed control method, and a single mobo header can only do one method. Now, with several headers, you can get around that because most mobo headers today can be set to use either method - you just have to match header Mode to fan type. Whether YOUR mobo can do this is why we need its specs.

Next, you need to distinguish between a Splitter and a Hub. A Splitter is a simpler device. It has ONE input arm with a female (with holes) connector on its end, and two or more output arms with male (pins) connectors into which you can plug your fans. It has NO other types of arms. It simply connects all of its fans to the header in parallel, and thus the header is the ONLY source of power for all the fans on that Splitter. Most mobo headers can supply up to 1.0 A max current to the total of all fans connected to that header, and that is the limit you must use. Splitters used to have a "bad rap" because people tried to connect too many fans (and hence too much current draw) to a single header, AND older fans often used more current than modern designs. Today the common case fans pull 0.1 to 0.2A each, so even four fans is well within the capability of a single header. The exception to that "rule of thumb" is LED fans (not the newer RGB fans with two cables from them). The LED fans that came out first have only one power cable to them and it feeds both the motor and the LED's, and that causes them to pull 0.3 to 0.5 A each.

A fan HUB is a different device. It has a third type or "arm" that ends in a Molex male or a SATA power connector, and that must be plugged into a power output from a PSU. The Hub gets power for all its fans from that PSU source and hence avoids the 1.0 A limit of the header. It draws no power from the header, but it does distribute the PWM signal from Pin #4 of the header to all its fans; this does NOT overload that signal source. But this means that the HUB depends entirely on its fans to use their PWM Mode capabilities - that is ALL its fans MUST be of the 4-pin type - AND that it can be used ONLY with a mobo 4-pin header that actually IS using the PWM Mode of control. I find that many sellers mislabel their devices as Splitters or Hubs when they are not. That's why I have described now to tell them apart.

The speed of a 3-pin fan can be controlled ONLY by changing the voltage supplied to it on Pin #2, which is called Voltage Control Mode or DC Mode. Since HUBS do NOT do things this way, you cannot use them with 3-pin fans. (There is one special Hub that is an exception to that "rule".) Thus if you are using 3-pin fans you really should be using a SPLITTER to connect more than one to a header.

The speed of 4-pin fans is best controlled by the new PWM Mode, although it CAN be controlled also by the older Voltage Control Mode.

The connection systems for 3- and 4-pin fans are very similar so you can always connect either fan type to either 3- or 4-pin headers and cable connectors. Among other things, this means that, when choosing a SPLITTER, it does not matter which type you get. Both types of Splitter will work correctly with both types of fans. BUT what is important is matching the fan type to the Mode that the HEADER is using to accomplish speed control.

OP, one item in your post struck me. You say you are not satisfied with the cooling performance you are getting, but ALSO say that you have deliberately slowed down some fans, presumably for noise reduction. Slower fans produce less cooling! If you want more cooling, first try letting all your fans run under automatic control so they DO produce the cooling required. THEN if you still need more cooling, consider whether more fans is the right way to go. OR, if you like the cooling but not the noise, consider replacing your fans with different models that will produce less noise for the SAME air flow.

I want to buy 6 Corsair ML120 4-fans and set them to about 50% and also use the one included fan on my Corsair H60 as bottom intake. I am most conserned about my GPU temps as they are usually at about 75C. I do not want to ramp up my fan speed, i have already tried but the noise level gets to high and gets quite annoying. I am using a Asus GTX 1070 Dual and a MSI B450-A Pro mobo. I want to set connect two of my front fans to the splitter and let the last of the 3 connected directly to the mobo and connect my two top fans to a splitter as well.

Also, will splitters do anything with the fan speed? Would connecting multiple fans to a fan splitter (not hub) change the rpm they are running? considering i will be setting them to about 50% each, would that draw to much power?

 

[Paperdoc]

To be sure I get all these correctly, your plan is:
3 x ML120 fans in front intake
2 x ML120 fans as top exhaust
1 x ML120 fan on the radiator of the H60i (2018) of the CPU cooler, mounted as rear exhaust
1 x Corsair (unknown model) 120 mm SP-type fan from the H60i system, as bottom intake

Yes, this can all work using just Splitters, with the right configuration settings.

First, the CPU cooler system is the H60i, but replacing its supplied fan with one of the ML120 fans. No problem. Now, the H60i installation is best done using the mobo's PUMP_FAN1 header for the pump unit, and the CPU_FAN header for the fan mounted on its radiator at the back. The pump unit has a 3-pin fan connector on its cable but it requires a constant full 12 VDC power supply so it runs full speed always. So configure the PUMP_FAN1 header to use PWM Mode. This is technically the wrong way to control a 3-pin fan, but it takes advantage of a fan design "quirk". When you connect a 3-pin fan to a header using PWM Mode, the fan always receives the full +12 VDC on Pin #2 and it never gets the PWM speed control signal from Pin #4, so it does run full speed all the time. The design of the H60i system intends this for pump speed, and does all control of the CPU temperature and cooling by varying the speed of the radiator fan. You will be using a 4-pin PWM style fan on that rad connected to the CPU_FAN header, so configure that header also to use PWM Mode and default automatic control.

That leaves six other fans for case ventilation - three front and two top by ML120's, and one bottom intake 3-pin fan. You will have four mobo SYS_FAN headers to power and control them. The bottom intake 3-pin fan needs to be on its own header that is configured to use DC Mode, because that's the only way to control its speed. All the other fans can be powered and controlled by SYS_FAN headers that are configured for PWM Mode. Those fans are spec'd to pull at max 0.225 A current per fan IF you have the ones with NO coloured LED lights in them. You have not specified this, but IF you are going to use the ML120 Pro LED fans, they are spec'd to consume 0.299 A max. In both cases, you could connect three such fans together using a Splitter to a single mobo SYS_FAN header and still be OK with a max current of 0.9 A or less, versus a fan header limit of 1.0 A. So with five such fans you could use two three-output Splitters like this

https://www.newegg.com/Product/Product.aspx?Item=N82E16812423163&Description=Coboc%20fan%20splitter&cm_re=Coboc_fan_splitter-_-12-423-163-_-Product

to make the connections to two mobo headers, leaving one header unused. OR, you could use two two-ouput Splitters like this

https://www.newegg.com/Product/Product.aspx?Item=N82E16812423160&Description=Coboc%20fan%20splitter&cm_re=Coboc_fan_splitter-_-12-423-160-_-Product

to connect pairs of fans to two headers and a single fan to the last header.

Although you plan to run all the case vent fans at half speed, at start-up time all of them will be fed for a few seconds the full 12 VDC supply to ensure start-up, and that's when max current is pulled. So the calculations for max current do apply, and the arrangements above are OK.

I get that you are concerned about noise, but I want to caution you about your plan. First, I really think the speed of the fan that is mounted on the radiator to cool the CPU should be under automatic control by the CPU_FAN header, and not set to a fixed lower speed. If you do this, most of the time it will be running slower because that is sufficient, but it also will be free to speed up when the CPU gets hotter because your workload has increased. This will happen automatically with no intervention by you. If you were to limit its speed to a fixed slow setting, YOU would be responsible for making sure that the CPU never overheats when you get busy.

A similar argument applies to the case ventilation fans, but with those there is less concern for overheating damage to the expensive CPU chip. Thus your plan to fix them all to be slower is probably OK. I encourage you try try using automatic control anyway, just to find out if a fixed slow speed DOES actually give you both lower noise AND adequate cooling under most conditions.

I recognize that, for the case vent fans, a significant concern is adequate supply of cool air into the case so that the Graphics card can have sufficient cool air to do its own automatic cooling. Unfortunately, no automatic fan control system on the mobo can take care of that for you, because the mobo has no access to temperature information from the graphics card. Mobo automatic control of case fans on the SYS_FAN headers is based on a temperature sensor on the mobo, and that does change fan speeds according to system workload as mobo components generate more or less heat. Roughly that also correlates with workload and heat generation on the graphics card, too, but there is no feed of graphics card temperature to the mobo.

 

[Paperdoc]

Thanks for Best Solution.