PSU is drawing 26W in standby

Hi,

I have a Corsair CS550M 550W power supply, which is an 80 Plus gold certified PSU, however, as per the title, when the PC is in standby, it is still drawing at least 26W.

When I built the PC, it was intended to be a low power one which I could leave on all the time.

I'm running Windows 10, but this happens when it has been completely shutdown.

I did not switch off the PC at the plug or on the PSU itself, but I would not expect it to draw this much power in 'standby'.

I have checked the settings in the motherboard, as well as disconnecting all USB devices, but it continues to draw power, unless I unplug the PC.

I've also checked the device I am using to see the power draw and it is working properly.

I believe that the problem is due to my Corsair PSU, although I understood that it should be very power efficient.

Mine does not meet EU standards.

I suspect that it has been happening since I installed the PSU, however, I just didn't expect there to be any significant power draw, so didn't check it.

Any advice?

Is there anything else which could be causing it?

Thanks.

well there is the 5VSB that is always powered on to be able to wake the PSU up when you press the button. i believe it also powers on the USB ports for charging when the PC is off.. so if you have a phone or a wireless mouse plugged in for example, the PSU may be charging them.

In bios there are energy saving options to disable some of these features on the motherboard level. But the 5V stand-by power rail is always on.

You can just reduce the amount of power used from it at the motherboard level after that.

I disabled the facility to charge from USB when the power is off.

The thing is, I've disabled all the options in the UEFI that I can find which may be using power in standby.

From what I read in the documentation, my PSU should be using maximum 0.5W in standby.

I also have a 2011 Mac Mini and that uses less power when it's turned on and idling (19W)!!

26W in standby is just too much.

I'd love to know what other users of this PSU see in terms of standby power consumption.

It’s not a Kill-A-Watt - I’m in the U.K. and haven’t seen those, but I expect it’s similar.

I can’t say for certain how accurate it is, but it’s consistent and the idle values for my Mac Mini are in line with the figures from Apple.

Likewise, if I connect the charger for my iPhone, when I disconnect the phone, the power draw drops to nothing.

It’s definitely drawing considerably more than 0.5 W when the PC is in standby.

Thanks for the suggestion; I’ll try disconnecting the motherboard and will report back.

Memory is:

HyperX FURY DDR4 HX424C15FB2/8 Ram 8 GB 2400 MHz DDR4 CL15 DIMM

How do you measure the power draw with a multimeter - do you use one of the clamp-on ones?

Hi,

No, I didn’t mean with the PC running. 😀

Sorry for my poor explanation.

What I mean is that when you close a browser, eg Firefox, it’s possible to save your open tabs. I tend do this a lot.

Then I shut down the PC.

When I start the PC again and open Firefox, all my open tabs are restored.

I don’t know how that information is saved - I assumed it was held in the memory, not written to the hard drive (I may well be wrong!).

I opened up my PC, but it’s a SFF case and I’d forgotten just how cramped everything is in there.

Unfortunately I think I’ll have to remove the fan and heat sink to get at the memory, and I can’t even see where the motherboard power connector is, so it’s an evening/weekend task.

😧

I’ll post back when I’ve checked those things.

Removed the RAM; still 26W draw.

Removed the 24 pin ATX power supply to the motherboard - still 26W draw.

The Fractal case has a fan, so I disconnected that, but no difference.

I have a Noctua NH-12 heat sink and fan, so I disconnected that, but then again, both of those are connected directly to the motherboard, so pulling the 24 pin cable would have eliminated them.

I can’t see what else could be the problem except the PSU.

☹️

Please let me know if you have any other ideas - I need to put my PC back together.

As a last throw of the dice, I switched off the power on the PSU then plugged the power cable back into the mains.

Result - 16W power draw.

So to me, there are 2 possibilities.

Either the power usage device I have is faulty/poorly calibrated, or something in the PC is still somehow drawing power.

RAM is still unplugged and motherboard 24 pin ATX connector disconnected.

Even so, for the PSU to be drawing 10W in standby, it’s not good.

Can there somehow be a residual power draw of 16W from the switched off PSU?!?

��

I don’t think the detector is faulty, based on how I’ve seen it work with other devices, but I can’t completely discount that possibility.

I don’t want to start cutting open cables to measure power draw with a multimeter though.

To add some perspective here as well, I have an ancient Dell Vostro 400 (12 years old), and according to my power monitor, that only draws 7W in standby.

My RM650 (2019) is very efficient with low standby power which is better than most older models by far.

Testing it showed about 75% at 30W load

when you switch it off, there's nothing at all going to the PSU.. sooooo that's that.

Anyway, i wouldn't trust those mains meters as far as i can throw them.. if you really want to know what power it draws, you'd really have to sacrifice a spare cable, open the sheathe to clamp meter that live wire

You can go to the moon on 16 watts. If a filter cap was leaky, it would explode on that much power.

Maybe look in the UEFI and activate ERP options. I believe that may be the most stringent one on stand by power. I had to use it to switch off motherboard RGB that would not turn off at all.

On the latest revision, i believe it should be 0.5 or 1W on standby.

But still.. switched off, it should be 0W since the PSU is disconnected from live.

Thanks for the suggestion; I’ll try disconnecting the motherboard and will report back.

Memory is:

HyperX FURY DDR4 HX424C15FB2/8 Ram 8 GB 2400 MHz DDR4 CL15 DIMM

 

How do you measure the power draw with a multimeter - do you use one of the clamp-on ones?

Clamp on meters do not work on cables that have the positive and negative all in one. They only work when clamped on to just the positive, otherwise the negative cancels the reading to 0.

The kill-a-watt meters are just fine for that sort of thing and will pretty accurately show down to 1w or even less. I know, I have used them on Corsair PSU's before.

I have lots of tools in the box for testing power supplies and even test equipment

I have had issues in the past with crap power supplies so I made custom split cables so I could measure power to a video card. This did not work as well as desired as many cards like the early RX 480 used excessive motherboard power. My Sapphire RX 480 however has a 8-pin PCIe connector so it uses mostly that for power.

I have even had an old PSU explode and start smoking. Lots of fun back in the old days.

Here's a shot in the dark.... Is the outlet you have that PC plugged into grounded? Hot and neutral are in correct order?

I tried it on 2 different outlets and both of them have been re-wired within the last 8 years, as my house was renovated (2 different electricians rewired these sockets).

I don’t think there’s any issue with the wiring.

At this point, I have no idea what’s going on with this PC.

Are there any reasonably low cost replacements I could get, which would give me a low idle power consumption?

Personally, i'd rather confirm the reading with a multimeter, just to be sure you don't spend money to replace a PSU for no good reason.

Even your old PC with 7W when off seems too much.