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Impact of switching on/off ATX PSU on a daily basis.

Caroline
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Good morning/evening/night everyone.

 

I've read dozens of posts stating "you shouldn't turn off your PSU because you'll damage it", but none went on the details about WHY.

There are power issues in my area, constant brownouts, outages, surges. Therefore before going to bed I usually shut down my computer and then flip the breaker on the back of the UPS to prevent night surges from damaging anything.

I know about inrush current required to load the caps but isn't the PSU protected against that? Will the components degrade even with the thermistors and filtering components there?

 

Can anyone provide proof to back such claims? articles, tests, videos...

 

Thanks.

Tender is the night

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If you're worried about surges, why not unplug it from the wall entirely?

 

As for switching the component on/off every day. It's a switch. Use it as intended and don't worry about the fake news. Just know switches can fail... but unplugging your computer from the wall entirely is a cheaper fix if the cable somehow goes bad.

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43 minutes ago, Caroline said:

I've read dozens of posts stating "you shouldn't turn off your PSU because you'll damage it", but none went on the details about WHY.

There are power issues in my area, constant brownouts, outages, surges. Therefore before going to bed I usually shut down my computer and then flip the breaker on the back of the UPS to prevent night surges from damaging anything.

I know about inrush current required to load the caps but isn't the PSU protected against that? Will the components degrade even with the thermistors and filtering components there?

 

Can anyone provide proof to back such claims? articles, tests, videos...

It is quite likely if you switch everything off every night, as we do here, you will destroy it in about 50+ years time.

 

And no, absolutely no proof. I've been switching off computers each night for nearly 40 years so that's the only 50 year proof I might have.

 

Oh, and don't go out the door as you might have an accident and don't stay in bed as more die in bed than anywhere else.

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There's 3 reasons often cited for not switching the PSU off all the time.

 

Switch wear:

The switches are rated for X number of cycles and excessive switching can break the switch. A PC power supply rocker switch will likely be rated for around 10,000 cycles. Even if you're turning it off and on every day that's more than 10 years, normally a switch will outlast the life of the power supply, but some switches might have poor tolerances or defects, bad batches etc and may fail sooner than what they're rated for. There's also a small arc of electricity between the switch contact points each time it is switched and that can degrade the switch further, but as long as you're not doing something stupid like holding the switch half way between off and on constantly breaking that contact causing it to arc it should be within the normal rated duty cycles.

I've personally seen switches fail prematurely, but I definitely wouldn't say it's a common failure. If you know what you're doing soldering on a new switch is easy.

Since you're switching it off at the UPS it wouldn't be the PSU switch that is getting the wear.

 

 

Inrush current:

Every time you switch the system on there is a brief surge of current as the hold up capacitors charge. Very generally speaking the larger the capacitors the higher the spike. Power supply manufacturers can mitigate this with an NTC thermistor which limits the current, but that adds extra cost and reduces efficiency slightly. To mitigate the efficiency losses they might use a bypass relay to bypass the thermistor after the initial inrush of current. Lower wattage power supplies (or cheaper power supplies) might not have any way of limiting inrush current. High end, high wattage units should always have at least an NTC thermistor, usually also a bypass relay as well. High inrush current can potentially damage the PSU, even with NTC thermistors to limit the inrush current, but since you mention you're in an area with a lot of brownouts and surges, the risk of issues caused by those would be greater.

 


Motherboard battery:

Your motherboards BIOS settings are stored in volatile memory and if power is lost those settings will be lost. The power supply normally supplies a small amount of power to keep the system powered, and without that the board uses a small CR2032 battery for power. The batteries will normally last a few years, 5+ years expected for most, but if you're constantly cutting power to the system the battery may drain faster and can fail after a year or two (it can really depend on the battery you get, you might leave the system off for 10 years and the battery will be fine). This can cause some configuration issues, like not finding the correct boot drive or needing to retrain for the memory each time it's turned on (causing longer boots, boot cycle). This might not cause any actual issues and is really more of an annoyance in most cases. The fix is pretty easy with just needing to replace the CR2032 battery which can be bought at most supermarkets for about a dollar or two.

 


And not really a reason why it's not recommended but it's just more hassle switching it off and on all the time and you have to wait for the system to boot instead of just resuming from a sleep state. It's generally better to leave it switched on, but your PSU isn't going to spontaneously explode if you do switch it off and on regularly. If you're experiencing brownouts and surges then it would be better to switch it off and unplug it from the wall than leave it powered on.

CPU: Intel i7 6700k  | Motherboard: Gigabyte Z170x Gaming 5 | RAM: 2x16GB 3000MHz Corsair Vengeance LPX | GPU: Gigabyte Aorus GTX 1080ti | PSU: Corsair RM750x (2018) | Case: BeQuiet SilentBase 800 | Cooler: Arctic Freezer 34 eSports | SSD: Samsung 970 Evo 500GB + Samsung 840 500GB + Crucial MX500 2TB | Monitor: Acer Predator XB271HU + Samsung BX2450

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40 minutes ago, johnt said:

If you're worried about surges, why not unplug it from the wall entirely?

Are your wall switches unreliable? This is presuming your wall sockets have switches.

Here it would be better to use the wall switch as unplugging it means stress on the plug or cable if clumsy.

If left in plugged into the wall, I've never ever had a switch fail.

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8 minutes ago, Spotty said:

Switch wear:

The switches are rated for X number of cycles and excessive switching can break the switch. A PC power supply rocker switch will likely be rated for around 10,000 cycles.

Switch life -
365 days x 10 years = 3650 operations. 10,000 is nearer 30 years.

"switch the system on there is a brief surge of current" which is why there is a choke in series with the rectifiers feeding the capacitor(s).

 

Battery for the BIOS settings - I suppose I'll have to replace a few in 20 years time. This is on computers turned off each day and are only on for half a day, 3 days a week.

 

Yes I have had to replace a BIOS battery. The computer had been on the shelf for about 5 years.

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11 minutes ago, RollyShed said:

Are your wall switches unreliable? This is presuming your wall sockets have switches.

Here it would be better to use the wall switch as unplugging it means stress on the plug or cable if clumsy.

If left in plugged into the wall, I've never ever had a switch fail.

The concern would be high voltage surges. A high voltage surge such as a lightning strike will blow through a household outlet switch even if it's in the off position. That's why it's best to unplug during a lightning storm so that the surge doesn't have a physical path to the appliances.

Also while it's mandatory (I think? I've never seen any without them) in Australia and NZ to have switches on the wall outlets, many countries don't have switches on their wall outlets (or it's far less common).

 

1 minute ago, RollyShed said:

Switch life -
365 days x 10 years = 3650 operations. 10,000 is nearer 30 years.

I was going off switching it off and switching it on again as separate "cycles" (about 13 years), but now I'm not actually sure if a cycle is measured as simply toggling the switch, or if a cycle is counted as toggling the switch both off and on.

Either way, like I said a switch should outlive the lifetime of the power supply, or at least its warranty. If it does fail it should be covered by warranty, and if it's outside of warranty replacing a switch in a PSU isn't difficult if you know what you're doing. I wouldn't normally recommend people open their PSU especially if they don't know what they're doing, but I know Caroline has mentioned doing some electrical work before so I'm sure it's something they would be capable of.

CPU: Intel i7 6700k  | Motherboard: Gigabyte Z170x Gaming 5 | RAM: 2x16GB 3000MHz Corsair Vengeance LPX | GPU: Gigabyte Aorus GTX 1080ti | PSU: Corsair RM750x (2018) | Case: BeQuiet SilentBase 800 | Cooler: Arctic Freezer 34 eSports | SSD: Samsung 970 Evo 500GB + Samsung 840 500GB + Crucial MX500 2TB | Monitor: Acer Predator XB271HU + Samsung BX2450

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A wall switch would be ideal for every day use. But @Spotty is spot on... it doesn't do anything for a power surge. The best practice is to unplug. I wouldn't worry so much about in rush current as the brown outs and outages are worse. And depending on how frequently the Op experiences a brown out each day, the cycle of unplugging once at the end of the night is less risky.

 

But really, you are in prime space for an uninterrupted power supply. This would solve your issues for brown outs and outages and possibly mitigate the in rush current concern. You also wouldn't need to unplug or switch the PSU off regularly. Except for lighting storms that can cause power surges. There is nothing to protect your wires from a power surge.

 

But if you experience a brown out weekly or even monthly. You need a UPS.

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13 hours ago, johnt said:

If you're worried about surges, why not unplug it from the wall entirely?

 

As for switching the component on/off every day. It's a switch. Use it as intended and don't worry about the fake news. Just know switches can fail... but unplugging your computer from the wall entirely is a cheaper fix if the cable somehow goes bad.

13 hours ago, Spotty said:

And not really a reason why it's not recommended but it's just more hassle switching it off and on all the time and you have to wait for the system to boot instead of just resuming from a sleep state. It's generally better to leave it switched on, but your PSU isn't going to spontaneously explode if you do switch it off and on regularly. If you're experiencing brownouts and surges then it would be better to switch it off and unplug it from the wall than leave it powered on.

Hi. I don't switch it off from the PSU but from the circuit breaker at the back of the UPS, which pretty much does the same as unplugging it from the wall. When there's a storm I do unplug it, just in case.

12 hours ago, Spotty said:

That's why it's best to unplug during a lightning storm so that the surge doesn't have a physical path to the appliances.

^^^^

 

13 hours ago, RollyShed said:

It is quite likely if you switch everything off every night, as we do here, you will destroy it in about 50+ years time.

 

And no, absolutely no proof. I've been switching off computers each night for nearly 40 years so that's the only 50 year proof I might have.

That's enough proof then. I've always switched them off as well and never had any issues, but the scaremongering keeps popping up in some topics about power supplies.

 

13 hours ago, RollyShed said:

Are your wall switches unreliable? This is presuming your wall sockets have switches.

Here it would be better to use the wall switch as unplugging it means stress on the plug or cable if clumsy.

If left in plugged into the wall, I've never ever had a switch fail.

13 hours ago, Spotty said:

Either way, like I said a switch should outlive the lifetime of the power supply, or at least its warranty. If it does fail it should be covered by warranty, and if it's outside of warranty replacing a switch in a PSU isn't difficult if you know what you're doing. I wouldn't normally recommend people open their PSU especially if they don't know what they're doing, but I know Caroline has mentioned doing some electrical work before so I'm sure it's something they would be capable of.

We're not at that level of electrical complexity yet, wall sockets are... simple, I had the idea of adding switches myself but the ones availabel for me are meant for lights and only rated to handle 5A, vs the 16 a socket can handle, it wouldn't work. I could use a switch that in turn energises a contactor that lets current flow to the sockets but that'd be comically overcomplicated when I can simply go and flip the UPS breaker off, or unplug it.

 

About me doing electrical work, not sure if I'd call it that, I just connect things together and try not to cause any explosions or fire, unless I want to :ph34r: oh, how to forget that one time I made a lightbulb with a pencil lead inside an empty jar, I forgot to add the series resistor but its glow was magnificent for a couple of seconds, then the cable caught on fire.

 

12 hours ago, johnt said:

A wall switch would be ideal for every day use. But @Spotty is spot on... it doesn't do anything for a power surge. The best practice is to unplug. I wouldn't worry so much about in rush current as the brown outs and outages are worse. And depending on how frequently the Op experiences a brown out each day, the cycle of unplugging once at the end of the night is less risky.

 

But really, you are in prime space for an uninterrupted power supply. This would solve your issues for brown outs and outages and possibly mitigate the in rush current concern. You also wouldn't need to unplug or switch the PSU off regularly. Except for lighting storms that can cause power surges. There is nothing to protect your wires from a power surge.

 

But if you experience a brown out weekly or even monthly. You need a UPS.

But I do have an UPS. I had repaired it already and don't want it to break once again due to a brownout followed by a surge.

 

I had installed a couple of outdoor lights and I'm familiar with NTC thermistors and MOVs as simple inrush/surge protectors.

Tender is the night

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43 minutes ago, Caroline said:

Hi. I don't switch it off from the PSU but from the circuit breaker at the back of the UPS, which pretty much does the same as unplugging it from the wall.

No, it does not do pretty much the same thing.
High voltage will allow electrical current to "jump" through an open switch (= arc), you actually need to physically unplug your stuff to protect it from surges.

That's what Spotty was referring to when he said :

14 hours ago, Spotty said:

The concern would be high voltage surges. A high voltage surge such as a lightning strike will blow through a household outlet switch even if it's in the off position. That's why it's best to unplug during a lightning storm so that the surge doesn't have a physical path to the appliances.


I don't think it's fear-mongering to tell you to leave your PSU switch alone.
Thermal cycling the NTC thermistor is easily the best way to make it fail.

There is no point turning your PSU off with the switch at the back, because it doesn't do anything for you :
- in case of surges : minimal surges can be alleviated with a surge protector, in case of large surges (e.g. thunder) current will still be able to make its way past the switch
- in case of brownouts : PSUs are capacitive loads, brownouts do not affect them when the PC is turned off.

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