[mkayokay]

A new semi-passive 850-watt fully modular PSU is around EUR 130, the Noctua fan around EUR 30.

I guess if you know electronics and how to safely handle the PSU internals, the risk of injury is low, but I personally would not risk it for EUR 100.

Also, if the only problem was the noisy fan, I guess selling it used would have returned most of the investment, leaving him with like EUR 50 in added cost. Compared to the price of a modern gaming PC, that's nothing (also avoiding not risking your life).

[tcdent]

I will put hundreds of dollars in Noctua fans into a second-hand chassis without thinking twice.

It's sometimes uneconomical from a cost-ratio perspective, but it is crucial to making datacenter-grade equipment actually useable at home.

[aaronmdjones]

I have a 12U 19 inch rack built into my computer desk, and I have a couple of NASes in it (2x HPC-8316SA-55RB1). The 40mm fans in the included CRPS PSUs are loud, whiny, and rattly, all at the same time.

I replaced all 4 of them with Noctua NF-A4x20s, wired to run at full speed all the time. They still report their speed so the IPMI management interface doesn't consider the power supply fan to have failed, but the PSU can no longer control the fan's speed.

The PSUs don't run any hotter and I can't hear them now.

I have a used Eaton PW9130 UPS in the bottom of the rack. The 80mm (exhaust) and 60mm (inverter heatsink) fans were likewise louder than I'd like. I replaced them with Noctuas too, again wired to run at full speed all the time, and the UPS' Web/SNMP card confirms it's still no hotter than 30'C internally. I can't hear that now either.

Hilariously, the most critical fan, the original inverter heatsink fan, is a 2-pin fan, so it probably can't even detect when it has failed (unless it's detecting fan failure by monitoring current consumption). The original rear exhaust fan uses a locked rotor sensor rather than a tachometer, which required a bit of bodging to convince the UPS that it has not failed. Oh well.

[ydj]

I’ve also done a noctua fan replacement on my ups. My worry is that they are rated for lower airflow than the original fans they replaced. Have you checked whether it stays cool when running on battery?

[aaronmdjones]

It's a permanent double conversion UPS; it's always inverting. You could activate the "high efficiency" bypass mode to directly connect the input to the output in the presence of mains AC input, but this would also pass through disturbances like fluctuations, harmonics, and surges, so I don't have it enabled. This wastes about 80W in my setup but whatever. I'm not worried about the inverter temperature is the point I'm trying to make; but I was considering this when I did it, which is why they're wired to run at full speed all the time.

[ahartmetz]

If you need pretty good fans for cheap as dirt, there is also Arctic Cooling.

[PaulKeeble]

They just never last. Arctic fans perform really well especially for their price but they all seem to develop problems. I have probably bought about 15 different Arctic fans from the F and P range and none of them survived 5 years, most were dead or developed noise within 1-2 years. Noctua on the other hand the old 80mm fan from the early 2000s still works just fine and remains quiet. Noctua fans are crazy reliable, they cost more too but I would suspect over the life of the fan they end up similar priced or cheaper.

[ahartmetz]

Arctic fans seem to last 10+ years for me. I haven't bought any recently though and I run them at 500 rpm or so, that's my strategy: many and large fans, running slowly.

[mrbigbob]

while arctic make fairly good high performing fans for cheap their bearings/acoustics are kind of bad. i bought 5 of the original p12 max fans with the ball bearings. they all made a chirping noise at various rpms (even after getting 5 new ones from arctic). the new p12 pro fans perform great but around 1200 rpms the motor is very loud and annoying

really wish arctic would now focus on the acoustics of their fans because its there weakest point. i wouldnt mind spending a bit more per fan if the sound profile wasnt just straight terrible which personally theirs are to me at the moment

[jojobas]

C grade high school physics understanding makes the risk exactly zero. Selling defective stuff without declaring is bad mojo, with declaring it just delegates the pain in the bum to someone else..

[doubled112]

I’ve been tearing things open after ignoring the “dangerous if opened” stickers since I was 8 years old. I’m in my 30s, you’d think something would have caused me harm by now, but no.

[jojobas]

There's a fair bit of survivorship bias in this. That said, modern power supplies use "bleeder resistors" to discharge the capacitors once powered off.

[scottlamb]

> There's a fair bit of survivorship bias in this.

Is there? This kind of statement has the potential to exhibit survivorship bias, but I feel like the opposite—"12-year-old dies replacing a power supply fan"—would make headlines. Definitely haven't seen that.

Capacitors should be respected for sure, but people don't routinely die in DIY electronics tasks.

[jojobas]

Electrical injuries claim some 1000 lives per year in the states, and 20% of all electrical injuries are sustained by children (lethal and non-lethal). I don't think every electrocuted child makes even local headlines.

[scottlamb]

Sobering for sure, but I think vanishingly few of those are from residual energy in capacitors in unplugged appliances during disassembly, [1] and certainly far from the "this forum is missing x people just like doubled112 because of tragedies" that I imagine when you say "there's a fair bit of survivorship bias in this".

[1] a quick search mentions things like damaged cords, the classic metal object into the outlet, etc. I installed tamper-resistant outlets everywhere in my house to prevent the latter as part of child-proofing. I think they're mandatory now in new construction. I also may have gone a bit overboard trying to instill caution in my children about this this particular risk; my son tonight asked me if he was okay after his sleeve brushed against the metal part of a USB-C connector while he was plugging in his tablet.

[account42]

That's more than an order of magnitude less than fatalities from cars. In my book, that puts it into "be careful" territory but far from "don't even think about it".

[heelix]

As a child, I remember being up in the attic with my grandfather. He touched some wires, swore (which was unusual for him), and said 'that was 220'. I still have a healthy respect for power.

[account42]

A lot of the risk is simply overstated. Yes, bad things can happen but that also goes for crossing the road yet we don't limit that to certified professionals. Just have some basic understanding of electricity, common sense, don't attempt the work while tired and you'll be fine.

[hobs]

Hilarious to read this on "hacker news" - replacing a standard fan is too dangerous! This is not styropyro.

[ycombinatrix]

PSU capacitors can kill you, even after being disconnected from mains power.

[victorhooi]

I think perhaps you might have not read the entire article? =)

The danger isn't so much in the fan, but in that the fan is INSIDE OF A COMPUTER PSU. There are mains AC voltages (220V, or 110V) here, and even if unplugged (which is should be) there are also capacitors in there, which you should definitely be cautious of.

I've worked in DC (datacenters) before - and I've seen people accidentally drop screws into power supplies...and well, electrical arc, boom, you can guess the rest. And in a domestic situation, a 4" cooling fan (yes, I know, larger) stopped suddenly due to a motor issue, and send flying bits of plastic shrapnel around (always wear eye protection!).

This isn't quite like tinkering with your little Arduino board, or Raspberry Pi.

If you did read the article =(.... I think that's a bit arrogant and disingenuous to make fun of people saying you should be cautious around things that are connected to AC mains, or that involve capacitors.

[hobs]

I appreciate that most folks talking about power on HN are talking about computers, but I decided to not become an electrician in an earlier life.

Taking standard precautions doesn't mean you suddenly shy away from doing basic maintenance. You can use iso alcohol to clean things even if its flammable, just don't use an open flame at the same time.

[umbra07]

> I've seen people accidentally drop screws into power supplies...and well, electric boom, you can guess the rest.

Are we talking like, bad electrical shock, hospitalization, death, etc?