Power Supplies with too high a rating

[Fike]

My power supply sounds like a metal grinding wheel digging into rusty nails.

My half-decent 465 watt Enermax power supply probably needs to be replaced.

The online calculators say I need a 455 watt power supply. I want a cool and quiet power supply. Higher wattage means higher heat and more fans making more noise.

So I am trying to figure out what rating to get in my PS.

I got a cool little gadget that tells me how many watts a particular device is pulling at any particular time. It is called a Kill-A-Watt. My PC has never drawn more than 245 watts under full load. When the PC is idle, it draws about 200 watts. When it is cranking away on a challenging game, it draws 245 watts.

I understand that higher wattage power supplies will have more headroom for smoother power signal...yada...yada...yada....but an extra 210 watts seems ridiculous.

I wonder if a high quality 350 or 400 watt power supply would be just fine. I see a few potential benefits of moving down in power supply ratings: less heat, less electricity consumption, less noise. I am running through a batter backup UPS, so power should already be pretty constant and stable.

Has anyone else measured the actual power consumption of their PC?

Are the Power Supply manufacturers selling us an overstuffed power supply? Have the wattage ratings become a proxy for quality instead of a simple representation of capacity?

 

[JasonE4]

A 500W power supply won't use 500W all the time. If your computer only needs 250W, a good power supply will only pull slightly above 250W from the outlet. A good higher wattage power supply will probably use less electricity, generate less heat, and produce less noise than one of lesser wattage.

 

[Operandi]

Originally posted by: Fike
Are the Power Supply manufacturers selling us an overstuffed power supply?

Since thats where the money is and people are stupid enough to buy into the marketing the simple answer is yes.

Originally posted by: Fike
Have the wattage ratings become a proxy for quality instead of a simple representation of capacity?

Sadly for many people thats also true.

If you don't intend to use SLi or Crossfire or dual CPUs (dual sockets, not dual core) you will most likely never need more then a 300-350 PSU.

 

[Fike]

Originally posted by: JasonE4
A 500W power supply won't use 500W all the time. If your computer only needs 250W, a good power supply will only pull slightly above 250W from the outlet. A good higher wattage power supply will probably use less electricity, generate less heat, and produce less noise than one of lesser wattage.

Yes. Obviously. As I said, my 465 watt power supply is drawing 245 at full load.

I am not sure about your contention that a higher watt power supply will draw less power and create less heat when it operates at lower wattages. I am not sure they are correlated.

 

[tkistre]

I'll be curious to see what others may say about this. I've been building computers (usually AMD systems) for about 10 years and usually go by their recommendations, of course with considerations to other equipment added, like amount of drives, video card, etc... Overall I've had good luck with power supplies.

One thing I've noticed, is when I've done repair work on manufactured computers (Dell, HP, Compaq, etc...), their power supplies are always very small, comparing what I put in the ones I build. For example, I remember when AMD released AthonXP processors and recommended 300w and above, I would work on a manufactured computer running AthlonXP and it would have a 185w power supply. I know they spec their system and know exactly what components they will put in, how much power is needed, and so forth. But a few friends I personally knew would add another hard drive, CD burner and a monster video card and still run everything off the the same small power supply with no problems.

 

[Roguestar]

Originally posted by: Fike
Are the Power Supply manufacturers selling us an overstuffed power supply?

Yes. Big numbers gets big money off the big idiots. Every so often you'll see people asking what 800/1000 watt power supply is best. Unless you're running quad-core SLI 8800GTX and then some, you'll never ever need that. But the bigger numbers and more LED fans you can stick on something, the more it'll sell to those with more money than sense who want the biggest e-penis possible.

 

[happy medium]

"I want a cool and quiet power supply. Higher wattage means higher heat and more fans making more noise. "

I would say a higher wattage psu will run quieter because it will rarely have to turn the fan on. Psu don't use 100% of there power so it's not hotter or more energy efficient.

"My half-decent 465 watt Enermax power supply probably needs to be replaced. "

Enermax makes good psu's . I'm wondering why this one crapped out if you were only using half it's capacity?

So the less heat, less energy consumption, less noise argument is thrown out the window.

I think you should find something with a large 120mm adjustable fan to be quiet if thats such a concern.
Do you ever plan on upgrading? You can get a good name brand 500watt psu for 70 bucks why sell you self short. Unless you want to buy another psu when you upgrade?

 

[Operandi]

Originally posted by: tkistre
I'll be curious to see what others may say about this. I've been building computers (usually AMD systems) for about 10 years and usually go by their recommendations, of course with considerations to other equipment added, like amount of drives, video card, etc... Overall I've had good luck with power supplies.

One thing I've noticed, is when I've done repair work on manufactured computers (Dell, HP, Compaq, etc...), their power supplies are always very small, comparing what I put in the ones I build. For example, I remember when AMD released AthonXP processors and recommended 300w and above, I would work on a manufactured computer running AthlonXP and it would have a 185w power supply. I know they spec their system and know exactly what components they will put in, how much power is needed, and so forth. But a few friends I personally knew would add another hard drive, CD burner and a monster video card and still run everything off the the same small power supply with no problems.

Read this.

 

[Fike]

Originally posted by: happy medium


"My half-decent 465 watt Enermax power supply probably needs to be replaced. "

Enermax makes good psu's . I'm wondering why this one crapped out if you were only using half it's capacity?

Do you ever plan on upgrading? You can get a good name brand 500watt psu for 70 bucks why sell you self short. Unless you want to buy another psu when you upgrade?

My current enermax still works fine. It just sounds like crap.

As for upgrading, I am running a pretty decent non-gaming PC. with 4 hard drives and 2 optical drives and a powered mid-range video card, it draws 245 watts under full load. My system is terminally upgraded, so I will need to start largely from scratch anyway.

 

[conlan]

Your kill-a-watt only tells you total system draw at the wall socket, not where those watts are going. You need to look at the PSU rail specs. Some 450W PSUs actually have more power to the 12V rail(s) then some 600w PSUs.

 

[SparkyJJO]

The noise you are hearing is probably the fan going bad. You could just buy a new fan and replace it, be cheaper than a whole new power supply. Just be sure it is unplugged first before popping it open

 

[happy medium]

Originally posted by: conlan
Your kill-a-watt only tells you total system draw at the wall socket, not where those watts are going. You need to look at the PSU rail specs. Some 450W PSUs actually have more power to the 12V rail(s) then some 600w PSUs.

This is a very good point my Enemax 350 watt psu has a 26 amp 12v+ rail. I'm sure this is more than most 450/500watt psu's.

 

[happy medium]

Originally posted by: SparkyJJO
The noise you are hearing is probably the fan going bad. You could just buy a new fan and replace it, be cheaper than a whole new power supply. Just be sure it is unplugged first before popping it open

Why didn't I think of that?:beer:

 

[Matthias99]

Originally posted by: happy medium

Originally posted by: SparkyJJO
The noise you are hearing is probably the fan going bad. You could just buy a new fan and replace it, be cheaper than a whole new power supply. Just be sure it is unplugged first before popping it open

Why didn't I think of that?:beer:

I was about to suggest it. You can probably get a fan that's even quieter than the one that was originally in there.

Also, someone earlier was saying that a "bigger" PSU would run cooler/quieter at low load -- this is not necessarily true. The amount of excess heat produced by the PSU is determined solely by its efficiency and the amount of power that it actually has to output. And given similar design -- the more heat it wastes, the louder it will be, since the fans will need to run faster.

Most PSUs are tuned to be most efficient somewhere around 60-80% of their rated maximum power output. If you only need 200W for your system, a high-efficiency 300W unit should be cooler and quieter than a 400W or 500W one. Some PSUs are pretty efficient at any output level, but buying way more than you need will still not do much for you.

 

[SparkyJJO]

Originally posted by: happy medium

Originally posted by: SparkyJJO
The noise you are hearing is probably the fan going bad. You could just buy a new fan and replace it, be cheaper than a whole new power supply. Just be sure it is unplugged first before popping it open

Why didn't I think of that?:beer:

Because I overclocked my brain so it runs faster than yours

I seem to have some memory stability issues though, maybe I pushed it too far

 

[Fike]

Originally posted by: SparkyJJO
The noise you are hearing is probably the fan going bad. You could just buy a new fan and replace it, be cheaper than a whole new power supply. Just be sure it is unplugged first before popping it open

That's a decent idea, but I have two concerns.

1) I don't know what size fan is in there, so I would need to disassemble it and then order a fan and wait with a computer half disassembled (or reassemble it between).
2) I understand that power supplies can have some honkin capacitors in there. Someone mentioned 24 amps on the 12 V rail. That is a truly dangerous amount of current. How do I make sure the capacitors are fully discharged without killing myself.

So, if for $40 I can get a good power supply, that would seem to be lots easier. On the other hand, this enermax cost me almost a hundred bucks 4 or 5 years ago, so it might be better quality than what I could get for $40 now.

 

[happy medium]

Originally posted by: Fike

Originally posted by: SparkyJJO
The noise you are hearing is probably the fan going bad. You could just buy a new fan and replace it, be cheaper than a whole new power supply. Just be sure it is unplugged first before popping it open

That's a decent idea, but I have two concerns.

1) I don't know what size fan is in there, so I would need to disassemble it and then order a fan and wait with a computer half disassembled (or reassemble it between).
2) I understand that power supplies can have some honkin capacitors in there. Someone mentioned 24 amps on the 12 V rail. That is a truly dangerous amount of current. How do I make sure the capacitors are fully discharged without killing myself.

So, if for $40 I can get a good power supply, that would seem to be lots easier. On the other hand, this enermax cost me almost a hundred bucks 4 or 5 years ago, so it might be better quality than what I could get for $40 now.

Heres a link to the spect of your psu. It looks like it has 2 fans in there exhaust and intake.
9cm fan intake, 8cm exhaust. It says ball bearing fan so it's probrobly just a bad bearing.
That auction goes for 6 days..... Mabe just buy it and have one for a spare? I bet you can get it for 35.00$ shipped .

http://cgi.ebay.com/Enermax-Whisper-465...1QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[tkistre]

Originally posted by: Operandi

Read this.

Very long, but also very interesting. It got very technical, more than I needed, but I did learn alot from it.

 

[SparkyJJO]

Originally posted by: Fike

Originally posted by: SparkyJJO
The noise you are hearing is probably the fan going bad. You could just buy a new fan and replace it, be cheaper than a whole new power supply. Just be sure it is unplugged first before popping it open

That's a decent idea, but I have two concerns.

1) I don't know what size fan is in there, so I would need to disassemble it and then order a fan and wait with a computer half disassembled (or reassemble it between).
2) I understand that power supplies can have some honkin capacitors in there. Someone mentioned 24 amps on the 12 V rail. That is a truly dangerous amount of current. How do I make sure the capacitors are fully discharged without killing myself.

So, if for $40 I can get a good power supply, that would seem to be lots easier. On the other hand, this enermax cost me almost a hundred bucks 4 or 5 years ago, so it might be better quality than what I could get for $40 now.

1) happy medium answered this
2) caps can't hold that much current, 24A is only for when the PSU is on. And 12V isn't enough to kill you or usually even shock you - unless you get your hands wet first To make sure it is all discharged though, unplug the PC, then push the power button. That'll drain anything left in there. I've done that and out of the dozens of PSUs I've taken apart not one has bit me yet.

 

[mcvan]

The online calculator you're using totally exaggerates the power need of your system.

Pay attention to the Kill-a-Watt , it s quite accurate, within about 1%. The 200w/245W AC you are measuring tells us a lot of things.

You don't list the model number of your PSU, but if it is not more than 2~3 years old, it probably has an AC/DC conversion efficiency of around 75%. (If it's older, it will be more like 70%). Use this number to figure out roughly how much DC power your components are pulling from the power supply.

At idle: 200W AC input x 0.75% efficiency = 150W DC output
At full power: 245W x 0.75% = 184W DC output

The numbers look about right, in line with similar systems I've measured for power consumption. Your PSU is capable of delivering 2.5 times more power than your system actually uses. You could get by with a good 300W PSU.

I agree with others who've said the fan bearings are going. It's simple to replace the fans if you have any wiring/ soldering skills -- and a little care.

--------------------

EDIT: I see you wrote it's 4-5 years old. That means 70% efficiency is more likely. This brings down the DC power delivered:

At idle: 200W AC input x 0.70% efficiency = 140W DC output
At full power: 245W x 0.70% = 171.5W DC output

 

[Moose1309]

I agree with those that say you only need around 300W, but you have to make sure it's a very good 300W one. Even Enermax, in my limited experience, don't start getting good until around the 400W models. Ever since I got my Seasonic S12 I've turned into a total shill - I love the thing. The 330W model should do you, or the 380 one.

and READ THAT SPCR ARTICLE, thank you Operandi for linking, I link to that at least once a month. In fact, also read a few of their PSU reviews. They give you efficiency scaling - so you can see, for instance, how a 600W PSU may be 78% efficient at 200W, where an equivalent 300W may be 86%. I've just pulled those numbers out of my orifice, but that's generally how it works.

 

[Jiggz]

So back to the OP, the concern is the noise, heat and energy consumption, in that order. Noise can be reduced by disassembling the PSU (four mounting screws and 4 cover screws) and blowing it clean. While in there check the fan for noise by manually spinning it with compressed air. If needed replace it with a Panaflo L series fan. Heat can be reduced by the above actions also. But heat is inherent to any PSU. What makes a cooler PSU is not based on rating or capacity but based on design and components use. Most of the heat is generated by power transistors and diodes and very little actually comes from the transformer or circuit bridges. Energy is also subjective in the sense different makes, different efficiencies. But if you consider everything being equal on two PSU's except for their rating or capacity with the load being identical, the PSU with the higher rating or capacity will consume more (not a whole lot but more). This is because the higher rated PSU will require higher excitation current since it uses larger transformers!

 

[Zap]

Originally posted by: mcvan
You could get by with a good 300W PSU.

Here ya go. 300W Fortron with 120mm fan and 80% efficiency for $32.

I was also gonna recommend this 360W Enhance that eWiz had, but they're OOS (they unlist OOS items). Potentially they'll get it back in stock. It has only an 80mm fan but is still fairly quiet. Efficiency wasn't too good, but it should be good quality and it even has a PCI-E 6 pin plug. Only $26 with Froogle link.

 

[Modelworks]

Be careful opening a power supply, even when its unplugged.
Those capacitors in there can be a bit large and are usually charged up with the wall current voltage.
They can hold there charge for years unplugged. A very nasty shock if your not careful.

 

[Fike]

Originally posted by: Zap

Originally posted by: mcvan
You could get by with a good 300W PSU.

Here ya go. 300W Fortron with 120mm fan and 80% efficiency for $32.

I was also gonna recommend this 360W Enhance that eWiz had, but they're OOS (they unlist OOS items). Potentially they'll get it back in stock. It has only an 80mm fan but is still fairly quiet. Efficiency wasn't too good, but it should be good quality and it even has a PCI-E 6 pin plug. Only $26 with Froogle link.

I think 300W is the bottom end of what I wanted to get. If I replace the PS, I was probably thinking of a 350 or 365 watt unit.

I will probably first try to open up my current supply and repair or replace the fan. Opening it up and blowing it out is a good idea that someone mentioned too.

Listening to others talk about voltage fluctuations on the processor, I think I am pretty lucky, because all my observations have it staying within .02 volts of the configured voltage. My overclock is working fine, so I might not want to throw a wrench in the works.