When fans can "send current back down the wire" per TechLinked, what protections do mobo & PSU have?

[NobleGamer]

[As for post categorization: This is partly about case fans and part post-mortem, hence not a "Troubleshooting" post, nor is it specific to PSUs or mobos.]

 

Context: TechLinked recently put out a video "How Often Should You Clean Your Computer?" that had a warning about cleaning case fans:

Quote

Having fans spin freely at high speed can actually send current back down the wire, and its a lot more expensive to replace a motherboard than to just buy another fan.

So remember to hold the fins down with your finger while you blow [compressed air on the fan].

 

My questions:

• What protections, if any, do motherboards and PSUs have for case fans sending current back down the wire?
• Do those protections have names that consumers like us can confirm against PSU specs?
• Or are these lower level protections that only labs like LTT can ascertain?
• Is it plausible that my old PSU's death (see story below) was caused by a case fan having physical resistance applied to it while the PC started up?
  • If so, is it because of this same type of current backflow referenced by TechLinked?

 

Why I want to learn:

PC builders like need to know the risks of case fans being messed with during cleaning or while running, or worse case how a defective case fan can put mobos & PSUs at risks.

If there is anything that mobos & PSUs have that can mitigate what was described in the TechLinked video, then we should learn about that.

 

The video reminded me of when just last week, my 8 year old 750W Antec HCG-750 PSU died in a way that might be explained by the above phenomena or something related to it...

 

My PSU explosion:

I put back together an old Intel 3rd gen build that was dormant for 2 years, already used compressed air on it, and got it running with a new Windows install and some updates including GPU drivers.  So its not like my PSU or any other part was inherently defective or dangerous as soon as I put it together.  I had the side panel off of my case, which has a plastic shroud facing the inside that funnels outside air toward the downdraft CPU cooler, instead of the CPU cooler drawing more air from inside the case.

 

One day I had the side panel off, I started the PC up, and I heard either the rear case fan or the CPU case fan rattling for about 1 second, and then I heard a loud pop from my PSU, the system did not have power, and there was a bit of a smoke smell.  I believe the case or CPU fan was rattling against the PC case's side panel plastic shroud leaning at an horizontal angle into the case.

 

What I can rule out for my PSU DOA:

• Electrical outlet wiring - This is completely new wiring that I oversaw a professional do, and IIRC it even uses an entirely new electrical circuit breaker
• Power surge & blatant home power issues - I have never known to have a power surge, nor any electronics killed by power plugs, nor brownouts, and only a few obvious outages during storms.
• Blatant miswiring or poor wire quality - If I screwed something up or wires deteriorated, then my rebuilt PC should've been DOA before installing Windows
• System power draw - Worst case, GTX 680 might have a peak power draw or transient spikes (I forget which) at 300W over its 2 separate pcie cables, even if doubling 3570K's TDP, that still leaves a few hundred Watts of overhead for the PSU.

I have no way to easily test whether the Intel 3rd gen mobo or its components are fried in addition to the PSU, as I don't want to pull my newer PSU from my current rig and at the moment I don't want to spend money on a different PSU running since I don't really need a second PC running for me right now - The rebuild was just for fun.

 

Thanks in advance, and thank you to the TechLinked team for teaching me something important that I wish I would have learned sooner.

[Vishera]

36 minutes ago, NobleGamer said:

[As for post categorization: This is partly about case fans and part post-mortem, hence not a "Troubleshooting" post, nor is it specific to PSUs or mobos.]

 

Context: TechLinked recently put out a video "How Often Should You Clean Your Computer?" that had a warning about cleaning case fans:

It's called EMF - Electro-Motive Force

 

When you spin a fan with non-electrical sources such as moving it with your hand or with the pressure from canned "air dusters" the fan will act as a generator -

Generating unwanted power that goes into the motherboard and may damage it.

[For Science!]

28 minutes ago, NobleGamer said:

[As for post categorization: This is partly about case fans and part post-mortem, hence not a "Troubleshooting" post, nor is it specific to PSUs or mobos.]

 

Context: TechLinked recently put out a video "How Often Should You Clean Your Computer?" that had a warning about cleaning case fans:

 

My questions:

• What protections, if any, do motherboards and PSUs have for case fans sending current back down the wire?
• Do those protections have names that consumers like us can confirm against PSU specs?
• Or are these lower level protections that only labs like LTT can ascertain?
• Is it plausible that my old PSU's death (see story below) was caused by a case fan having physical resistance applied to it while the PC started up?
  • If so, is it because of this same type of current backflow referenced by TechLinked?

 

Why I want to learn:

PC builders like need to know the risks of case fans being messed with during cleaning or while running, or worse case how a defective case fan can put mobos & PSUs at risks.

If there is anything that mobos & PSUs have that can mitigate what was described in the TechLinked video, then we should learn about that.

 

The video reminded me of when just last week, my 8 year old 750W Antec HCG-750 PSU died in a way that might be explained by the above phenomena or something related to it...

 

My PSU explosion:

I put back together an old Intel 3rd gen build that was dormant for 2 years, already used compressed air on it, and got it running with a new Windows install and some updates including GPU drivers.  So its not like my PSU or any other part was inherently defective or dangerous as soon as I put it together.  I had the side panel off of my case, which has a plastic shroud facing the inside that funnels outside air toward the downdraft CPU cooler, instead of the CPU cooler drawing more air from inside the case.

 

One day I had the side panel off, I started the PC up, and I heard either the rear case fan or the CPU case fan rattling for about 1 second, and then I heard a loud pop from my PSU, the system did not have power, and there was a bit of a smoke smell.  I believe the case or CPU fan was rattling against the PC case's side panel plastic shroud leaning at an horizontal angle into the case.

 

What I can rule out for my PSU DOA:

• Electrical outlet wiring - This is completely new wiring that I oversaw a professional do, and IIRC it even uses an entirely new electrical circuit breaker
• Power surge & blatant home power issues - I have never known to have a power surge, nor any electronics killed by power plugs, nor brownouts, and only a few obvious outages during storms.
• Blatant miswiring or poor wire quality - If I screwed something up or wires deteriorated, then my rebuilt PC should've been DOA before installing Windows
• System power draw - Worst case, GTX 680 might have a peak power draw or transient spikes (I forget which) at 300W over its 2 separate pcie cables, even if doubling 3570K's TDP, that still leaves a few hundred Watts of overhead for the PSU.

I have no way to easily test whether the Intel 3rd gen mobo or its components are fried in addition to the PSU, as I don't want to pull my newer PSU from my current rig and at the moment I don't want to spend money on a different PSU running since I don't really need a second PC running for me right now - The rebuild was just for fun.

 

Thanks in advance, and thank you to the TechLinked team for teaching me something important that I wish I would have learned sooner.

The problem is when you spin a fan manually while it is plugged in. A fan spinning fast powered by the motherboard is not a problem. If your fan is being slowed down artificially, this may put more strain on the motor hub, but does not send current "down the motherboard", so even at the worst case will only damage the fan and not the mobo/psu. I think your PSU dying is not related to the fan.

[BobVonBob]

37 minutes ago, NobleGamer said:

What protections, if any, do motherboards and PSUs have for case fans sending current back down the wire?

Generally motherboards will have some diodes to prevent current from flowing the wrong way, but not all do and even when they're present they have limits.

 

37 minutes ago, NobleGamer said:

Do those protections have names that consumers like us can confirm against PSU specs?

Nope.

 

37 minutes ago, NobleGamer said:

Or are these lower level protections that only labs like LTT can ascertain?

It could probably be confirmed by chasing the fan's power backwards to find any diodes in the path. It could be done by an individual, but it's difficult. Proper confirmation would involve potentially destructive testing of a motherboard.

 

37 minutes ago, NobleGamer said:

Is it plausible that my old PSU's death (see story below) was caused by a case fan having physical resistance applied to it while the PC started up?

Maybe, but it seems unlikely to me. Motors like the ones in fans draw the most current when they're stalled, but even at full stall it wouldn't even scratch the amount of power used by your CPU or GPU. I'd also expect the motherboard to give up before the PSU if a fan was drawing too much power. Maybe that PSU had a really poor 12 volt rail going to the 24 pin connector?

 

37 minutes ago, NobleGamer said:

If so, is it because of this same type of current backflow referenced by TechLinked?

No. What TechLinked was referring to is how a fan spun by means other than its motor will create a current. Motors and generators are basically the same thing but in opposite directions. By spinning the fan its motor turns into a generator which backfeeds the motherboard. This is different from your fan which was stopped from spinning, which makes the motor try to work harder to get it to spin.

[NobleGamer]

1 hour ago, For Science! said:

If your fan is being slowed down artificially, this may put more strain on the motor hub, but does not send current "down the motherboard", so even at the worst case will only damage the fan and not the mobo/psu. I think your PSU dying is not related to the fan.

Thanks for the insight. It conceptually makes sense that it would not be likely caused by the fan, but I have to admit that its hard for me to write it off as pure coincidence that the one time in 6-8 years of this PC running that I start it up with huge artifical strain on a fan, the PSU happens to end up dying.

 

Another theory that someone else shared was:

Quote

I'd also expect the motherboard to give up before the PSU if a fan was drawing too much power. Maybe that PSU had a really poor 12 volt rail going to the 24 pin connector?

What do you think of the 12V rail issue theory?

[NobleGamer]

1 hour ago, BobVonBob said:

I'd also expect the motherboard to give up before the PSU if a fan was drawing too much power. Maybe that PSU had a really poor 12 volt rail going to the 24 pin connector?

Interesting theory. If I opened my old PSU outer shell carefully, is there a way to visually determine the condition of the rail? What about with a basic multimeter of mine?

[BobVonBob]

18 minutes ago, NobleGamer said:

Interesting theory. If I opened my old PSU outer shell carefully, is there a way to visually determine the condition of the rail? What about with a basic multimeter of mine?

I'd suggest not opening a PSU unless you know what you're doing. They've got monster capacitors in them that are easily capable of killing you. If you heard a pop there's probably a big brown stain somewhere that you might be able to see through the outer case.

 

I don't know much about PSU autopsies, and that 12v rail theory was a guess based on where the power for fans comes from. I think the Antec HCG series was from the days when every manufacturer was touting how big and strong their single 12 volt rail was, which makes that theory seem even less likely.