Is there such a thing as too little power draw from a PSU?

[AlliedVera]

Hi, guys!

I'm wondering, if pulling a small load can harm a PSU?

In my situation I have a Thermaltake 550W PSU(80 bronze, if it matters). And I'm running a GTX970 from it. Nothing else. It draws power anywhere between 13W up to 205W. 

I've noticed a sort of a squeal, when benchmarking the GPU or the CPU, and it sometimes isn't there at all. Sometimes, playing games, the squeal shows up after a while. I'm pretty sure the sound comes from the PSU. Also, I've bought it only recently, but I've heard that lower tier Thermaltakes should be avoided. 
By asking the question, I sort of just want to know, if the squealing could've showed up because of the somewhat small loads.
I've heard somewhere, that if you run a 2xPSU setup, you should add something on the 5V rail too, as to balance the load? What's that all about?

 

I'll appreciate any kind of answer you'll be able to give me. 

Thanks!

EDIT: I put my ear next to the PC again, and now I think, that the noises are coming from the other PSU

the other one is a Lenovo proprietary 14pin PSU. I'm waiting for a MOBO upgrade, to start using only the Thermaltake.

Anyway the questions themselves are unchanged.

Edited September 7, 2021 by AlliedVera

[RONOTHAN##]

2 minutes ago, AlliedVera said:

if pulling a small load can harm a PSU?

There isn't really such thing as too little a load on a PSU. Power supplies tend to do better when pulling a smaller load.

2 minutes ago, AlliedVera said:

I've noticed a sort of a squeal,

It's probably coil whine, it's pretty common on cheaper power supplies. Not necessarily dangerous, but a sign that the PSU is using cheaper components that in turn might be dangerous.

3 minutes ago, AlliedVera said:

but I've heard that lower tier Thermaltakes should be avoided.

Yes, at all costs. They have a tendancy to blow up, and if you're still in the return window, it's not a bad idea to return it and buy a better PSU (assuming you got a lower tier unit).

4 minutes ago, AlliedVera said:

I've heard somewhere, that if you run a 2xPSU setup, you should add something on the 5V rail too

That's because, particularly for older and cheaper power supplies, they weren't designed to have their entire load given through the 12v rail and expected at least something to use 5v on the unit, and if enough wattage was drawn through the 12v rain, the PSU would blow up. Better designed PSUs don't do this, but that Thermaltake unit might not be the highest quality unit and therefore might. That being said, a dual PSU setup is basically never recommended outside of very specific circumstances, and you're much better off using one better unit rather than two meh-grade units.

 

[mariushm]

Actually there is such a thing as too small load... but it's not the case here. 

 

Older designs of power supplies needed a bit of power consumption on the voltages they output in order to stabilize the voltages coming out. Some had load resistors inside, components that would simply waste around 1w of power in the form of heat, just to provide that minimum amount of power consumption. 

Your video card consumes at least 10w or so on idle, and your power supply is modern enough that this scenario is not the case here.

 

Some designs don't like it when there's too much imbalance in the outputs... as in draw too much power from 5v but nothing from 12v, or as is in your case you're basically drawing only 12v and the 3.3v and 5v are unused. 

I don't think your psu model is one of those power supplies. 

 

[AlliedVera]

12 minutes ago, RONOTHAN## said:

Yes, at all costs. They have a tendency to blow up, and if you're still in the return window, it's not a bad idea to return it and buy a better PSU (assuming you got a lower tier unit).

I got the Thermaltake Litepower 550W, part number: LTP-0550P-2. It's a 2017 model. I guess it has to be a low-tier PSU, since I can't imagine getting a cheaper 550W PSU. I paid 35 Euros for it. I have a 2 year warranty, but I'm pretty sure, they won't be taking returns. Would you say that I'm safe using it within the warranty period, or I should really get maybe a Chieftec or a Corsair one ASAP?

[mariushm]

Chieftec is hit and miss, mostly miss... i'd categorize it lower than thermaltake. Corsair... depends on the model. If it's VS or some other low end... I'd pass. 

 

That litepower is not that bad, and should handle the 970, which consumes as much as a RX 570, around 175 watts. 

Keep in mind that it can do only 38A on 12v, basically 450w, so look at it as a 450w power supply, not a 550w power supply. 

 

Unless you get a really good deal on a Corsair PSU from a decent series, I'd keep this thermaltake power supply. 

[TRS80]

 

1 hour ago, AlliedVera said:

I'm wondering, if pulling a small load can harm a PSU?

 

 I would say yes, over time from heat. You definitely run the risk of burning out a component inside your PSU from the excess generated heat during prolonged periods operating at low efficiency. Just have a look at the different PSU efficiency curves.

[mariushm]

Just now, TRS80 said:

 

 I would say yes, over time from heat. You definitely run the risk of burning out a component inside your PSU from the excess generated heat during prolonged periods opereting at low efficiency. Just have a look at the different PSU efficiency curves.

Well, yes and no... I mean you're mostly incorrect. 

Even if we're talking about lousiest 50% efficiency at low output, a power supply producing 10-20w would generate 5-10w of heat. That's so small it doesn't matter. The heatsinks inside are big enough and natural air movement inside the power supply is sufficient to keep all components within reasonable temperatures, so the power supply wouldn't be affected in any significant way.

This is before we even talk about fan adding extra airflow and providing more cooling - I'm talking about the scenario where we have a hybrid power supply which turns off the fan below some amount of output or below some temperature threshold. 

 

Consider it's a 500-650w power supply that would dissipate more than 50w as heat when running at 500w+ output. The power supply heatsinsk and fans are sized to keep the psu cool. 

 

This aside, there are shitty power supplies that break after a few years because of the 5v stand-by circuit, due to bad circuit design and improper cooling.

 

The 5v stand-by is like a separate power supply inside the power supply which is always on, even when you turn off your PC.  You could picture it like a small usb charger inside the power supply, it's always ready to give power to something, and typically the motherboard chipset consumes a tiny amount of power (like 0.1w or something like that) using that energy instead of the onboard battery to keep the clock and settings.

Also, depending on the bios settings like Wake On LAN, wake on modem, on keyboard press.. the chipset can provide stand-by power to pci-e slots so that you could send a specially crafted data packet to your network card which would be detected by the bios and make the bios turn on the PC, thus making it possible to remotely turn on the PC, or wake the PC when a fax is coming (modem detects incoming call and tells bios to wake up the pc, so that the software can receive the fax) 

 

SOME designs don't put the components for this 5v stand-by circuit on heatsinks to save a few pennies, because the component itself would not get too hot (for example they can run up to 125c, but during regular use they run up to let's say 70c so heatsink is not required) , but other components like electrolytic capacitors which have to be placed close to those components are more sensitive to heat because they contain a liquid or semi-liquid substance inside called electrolyte.

So while PC is working, that capacitor is subjected to 50-70c of heat, while pc is off the circuit is still output some power but it's cooler, let's say 40c, but it's still warm and still affects such capacitors.

Over time, years, the capacitor's electrolyte can degrade from this heat and its properties degrade, and once the properties go below some threshold, the chip that produces the 5v stand-by can no longer filter the output and provide 5v stable voltage and the result is a faulty power supply that causes PC to randomly reset, or to make your motherboard boot cycle several times until it manages to start and work.

 

[TRS80]

2 hours ago, mariushm said:

Over time, years, the capacitor's electrolyte can degrade from this heat and its properties degrade,

Pat yourself on the back, it took you hundreds of words to say what I did in a sentence.

Great explanation though, thanks.

[mariushm]

No, you said something completely different and only the first sentence was correct.

 

I would say yes, over time from heat

 

Well, yes, a generic statement is correct. Anything can go bad over time, from heat.  The sky is blue, water is wet, not helpful.

 

You definitely run the risk of burning out a component inside your PSU from the excess generated heat during prolonged periods operating at low efficiency

 

This is incorrect. A modern power supply would operate at low efficiency only at very low output, very low wattages, therefore the generated heat would be equally low, and therefore would not cause problems or any significant amount of damage. 

There's no "excess" generated heat... it's just efficiency losses, normal for any product. 

 

Just have a look at the different PSU efficiency curves.

 

This is completely pointless addition and doesn't introduce anything useful or prove anything. As a matter of fact, pick any random efficiency curve on the first page of results and you'll see that even at less than 50w output, most power supplies are at least 80% efficient. 

Let's be ridiculous and say a pc consumes 25w idling - that means that in order to produce 25w to components, the power supply takes 25w * 100% / 75% = 33 watts from the mains to produce those 25w. 

Those 8w of losses would be spread across the WHOLE power supply, in the bridge rectifier that converts ac to dc, in the active pfc circuit which boosts the rectified dc to 400-420v dc, in the transformer that converts 400v+ dc to 12v and in the dc-dc converters which convert 12v to 3.3v and 5v and in the mosfets that rectify and stabilize the 12v output from the transformer. 

There's no single point of heat, those 8 watts are spread across the whole psu in multiple heatsinks, on some designs through the psu case itself (mosfets on the bottom pcp thermally coupled to the case) 

It's not worse or better than running at 100-200-500w with 85-90-95% efficiency ... the more components consume, the more heat will be generated, and the cooling has to keep up with everything.

 

 

 

 

[Juular]

With older, group regulated PSUs - yes. Like your Thermaltake Litepower. But in that case the PSU would either shutdown or it's voltages would go out of specifications, neither of which would harm the PSU itself but out of spec voltages may potentially if not harm the PC, but induce the instability. And yes, that happens not because the load is low exactly, but because it's unbalanced, these PSUs were designed when the very high load on 12V and almost no load on 5V & 3.3V weren't a thing like with modern PCs.

[TRS80]

13 hours ago, mariushm said:

Well, yes, a generic statement is correct. Anything can go bad over time, from heat.  The sky is blue, water is wet, not helpful.

Yes it was generic because I don't see the use of reading a novel just to explain a very simple question. Most of us [speaking for myself] are not Gamers Nexus students so your whole speil was not necessary. Heat kills period.

 

Don't contradict yourself. Now you get into this long explanation "as a matter of fact" and say it not likely [burn out the PSU] to happen. But in the post before you say "Over time, years, the capacitor's electrolyte can degrade from this heat" bla, bla, bla..

 

My original statement was a blanket k.i.s.s.- I see you take this very seriously. Hmmm, maybe you are the Gamers Nexus? Anyway, I do appreciate the details as I have been trying to decide between a 750 and 850W psu. Based on what you are saying I think it would be okay to get an 850W psu for further futureproofing.

 

Carry-on...