[SOLVED] Placing ice for intake fans?

Feb 1, 2021
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Just curious if I were to place an ice pack right in front of my front intake fans would cool the pc a few degrees. I have thought that the water from condensation might be sucked inside the case by the fans since mine has a mesh front, but I'm not sure. No problems with the PC at all, just curiosity.
 

Paperdoc

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Not so. The speed of older 3-pin fans CAN be controlled automatically exactly as those of 4-pin fans. This only requires that the mobo header be configured to use the correct METHOD of fan speed control. A 3-pin fan's speed is controlled by changing the power supply VOLTAGE from Pin #2 of the header. For a 4-pin fan, that Voltage is kept at the full 12 VDC, and then a new PWM control signal is sent out on Pin #4. Inside the PWM fan's case there is a special chip that uses that PWM signal to modify flow of current from the 12 VDC supply line through the motor windings, and THAT changes the fan's speed. If you connect a 3-pin fan to a header using the new 4-pin PWM Mode, it never gets the PWM signal from a non-existent Pin #4 connection, but it could not use that anyway because it has no special chip. Thus, it runs full speed all the time. BUT if the header is configured to do the older method of control - that is, to vary the VOLTAGE on Pin #2 instead of sending out a PWM signal on Pin #4 - the header CAN exercise over the fan exactly the same control of speed on a 3-pin fan.

That applies no matter how the header is configured for the PROFILE of its control work. That is, HOW the system decides what speed the fan should run. AFTER that decision is made, the matter of what METHOD the header uses to convey that instruction to the fan is the MODE of operation for the header, as above. Selecting a fixed speed, or imposing a custom "fan curve" for a header is part of the DECISION process, not the MODE. So no matter how you set its decision or Profile process, you still need the header to use the correct MODE of manipulating fan speed.
 

Lutfij

Titan
Moderator
Welcome to the forums, newcomer!

You are on the right track of mind when you were concerned about moisture. Please don't attempt to do what you've stated above, the humidity will only hamper the system, worse, might cause layers i your motherboard/GPU/ram PCB's to fuse/ground and then fry components.
 

HWOC

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Jan 9, 2020
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Yeah I wouldn't recommend it, but theoretically the intake air would be cooler, and thus the inside of your PC. Or put the PC in front of a freezer when the freezer door is open. I wonder how long would it survive inside a chest freezer...
 

USAFRet

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Mar 16, 2013
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Yeah I wouldn't recommend it, but theoretically the intake air would be cooler, and thus the inside of your PC. Or put the PC in front of a freezer when the freezer door is open. I wonder how long would it survive inside a chest freezer...
The freezer will die.

That concept has been tried many many times.
The fridge/freezer compressor and motor is not designed for a constant ON cycle, with an active heat source inside the box.
It will wear out rather quickly.
 

Paperdoc

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All the points above are good. But I'll add one more. The way an automatic cooling system works (both the CPU cooling system, and the case ventilation system) is that it monitors the actual temperature measured at a relevant sensor (inside the CPU chip, or on the mobo). For each of those two systems, the mobo has a pre-set target for what that temp should be, and a set of values for what speed signal to send to the fan(s) for that cooler for whatever temp is measured. (On many systems you have an option to set your own "fan curve" for this if you wish). As your workload changes, resulting in measured temperature changes, the system alters the relevant fan speed signals accordingly. In your hypothetical process, OP, what would happen is that the air entering the case over the ice block would be marginally colder, resulting in better heat removal from the warm items being cooled. Since that would reduce the actual TEMPERATURE at the sensors, this might result in the automatic system reducing the fan speeds since the cooling is better, and then the real operating temperatures would NOT change. All that would change is the fans would operate a little more slowly. It is also possible that the improved cooling would be so small that the fan speeds would not change, and the actual measured temps might drop by a degree or two, but not much really.

Bottom line: you'd gain almost nothing.
 

HWOC

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Correct me if I'm wrong, but the above is only true if you use PWM fans. With 3-pin fans for example, their rotational speed will not change automatically. Or, like you said, if you set your own fan curve, or lock the fans to a specific speed.
 

Paperdoc

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Not so. The speed of older 3-pin fans CAN be controlled automatically exactly as those of 4-pin fans. This only requires that the mobo header be configured to use the correct METHOD of fan speed control. A 3-pin fan's speed is controlled by changing the power supply VOLTAGE from Pin #2 of the header. For a 4-pin fan, that Voltage is kept at the full 12 VDC, and then a new PWM control signal is sent out on Pin #4. Inside the PWM fan's case there is a special chip that uses that PWM signal to modify flow of current from the 12 VDC supply line through the motor windings, and THAT changes the fan's speed. If you connect a 3-pin fan to a header using the new 4-pin PWM Mode, it never gets the PWM signal from a non-existent Pin #4 connection, but it could not use that anyway because it has no special chip. Thus, it runs full speed all the time. BUT if the header is configured to do the older method of control - that is, to vary the VOLTAGE on Pin #2 instead of sending out a PWM signal on Pin #4 - the header CAN exercise over the fan exactly the same control of speed on a 3-pin fan.

That applies no matter how the header is configured for the PROFILE of its control work. That is, HOW the system decides what speed the fan should run. AFTER that decision is made, the matter of what METHOD the header uses to convey that instruction to the fan is the MODE of operation for the header, as above. Selecting a fixed speed, or imposing a custom "fan curve" for a header is part of the DECISION process, not the MODE. So no matter how you set its decision or Profile process, you still need the header to use the correct MODE of manipulating fan speed.
 

rubix_1011

Contributing Writer
Moderator
This is correct - rpm vs voltage but the header needs to know which it is using which can be as easy as an 'AUTO' discovery mode, or set specifically if you know the type of fan. This is also why motherboards usually have the ability to manage fan speeds based on PWM or voltage/DC as either are possible from most headers, including defining other headers as an AIO pump or other item.
 

HWOC

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Yes indeed. I forgot about that, even though I was in my own BIOS just a few days ago playing with those settings, since I have a mix of 3-pin and 4-pin PWM fans. :LOL:
 

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