A few questions about UPS and also surge protectors

[Anonymous user]

Hi, I've a few questions regarding UPS and also surge protectors:

a) How do I calculate the wattage used for my PC? Do I use a PSU calculator or if not, what should I use?

My setup is as below:

P4 3.2 ghz + esys motherboard
ST520-PAF
2 80 GB Sata hdds + 1 IDE hdd(I'm probably going to trade most of these for a 640 gb hdd)
8600GT card
1 DVD combo drive: GSA-h62n
1 usb Govibe DAC(no idea what the wattage is) + BeyerDynamic DT440(100 mW)
Logitech EX90 wireless mouse + keyboard
2wire 2701HGV-E
Samsung 2253LW
1 external hdd with its' own power plug

Edit: am considering the APC Back-UPS ES 525. I hope it will be enough. :0
http://www.apcc.com/resource/include/techspec_index.cfm?base_sku=BE525-AS

b) I know that it is not recommended to plug in a UPS into a surge protector and vice versa. So, my question is: for all of your other equipment, how do you hook it up? I'm assuming that not everyone buys a UPS with as many as 6 to 8 outlets!

Message was edited by: Lucifiel


Thank you! 🙂

Message was edited by: Lucifiel

Message was edited by: Lucifiel

Message was edited by: Lucifiel

[Anonymous user]

First thing you should know beforehand is how many watts your gear consumes and for knowing that there are some ways, the cheapest way is to use an online calculator like this one:

http://extreme.outervision.com/psucalculatorlite.jsp

This is the most accurate online power calculator you can find, but I like to take a different path for sizing an UPS, even if you equipment will never or almost never use all the PSU Power.

You said you got a 520W PSU which I assume is an APFC one. So let's start from there.

If you have a 520W PSU it means it has the potention of some day drawing 520W from the UPS. It doesn't mean it will always be drawing 520W from it, unless the components inside your computer demands that or when the PSU is being stated which is called inrush current.

Well, APFC PSUs are much more efficient regarding the Volt/Ampere ratio usage which means a less powerfull UPS or Voltage Regulator or whatever thing that has a transformer built-in, can be used, within certain limits. Let me give you an exemple.

One 520W non-APFC PSU has a tipically 0.60 power factor which basically means that the relationship between Voltage and current is not reciprocal - the voltage lags in relation to the current. So a 600VA rated UPS is not capable of suppying 600Watts. Volts x Amperes = Watts. So why 600VA does not equal 600W??

As I said the common power factor found in most switched mode power supplies, those without APFC, has a .6 power factor, the current is out of phase in relation to the voltage, so a 600VA power transformer inside any UPS would at best supply 360W - > 600 x 0.6.

Now the APFC PSUs. These PSUs, which are very common today, as the name says, it is power factor corrected which means the power factor can be as high as 0.99, the current and voltage is almost in phase with each other. In this case, a power transformer rated at 600VA would supply almost 600W without overheating.

But you have to have in mind that there are other PSUs, plugged to the UPS. There is the PSU of your monitor, printer... and those are not APFC so you should put that into the power calculation, they have a .6 PF.

The other thing you should consider is the effiency of the PSUs. If your PSU is rated as 80% efficient, this means it wastes 20% of all the watts supplied. For exemple:

20% of 520W is 104W which tells us your 520W PSU can draw a total of 624W from the UPS at full load. So you should start from this number for sizing an UPS. You should buy one that is capable of suplying 624W and since your PSU is APFC, one 750VA UPS is enough for you, but i'm not counting here the monitor, printers and other stuff that you might have. And if your PSU is not an APFC one, 520W turns out to be 866VA -> 520 / 0.6 without counting the efficiency losses and you have to have at least and 1000VA UPS, an 1200VA or bigger one would be a better choice.

And regarding the surge protector, the way you should use it together with an UPS, in my opinion there is no problem connecting the UPS to a Surge Protector unless you don't overload it with stuff. You should not plug more then 1500W to a cheap surge protector or 15A. I would recommend no more than 10A though. Now plugging a surge protector to an UPS is not a very good idea. I've done that once and there isn't a problem at a first moment. The kind of wave supplied by the UPS's while on battery does not make MOVs conducts as some might say, but in case of a surge happens, the surge protector might shunt the excess voltage and current before the UPS does and tha has the potential for demaging the UPS board and components since a lot of energy is diverted to the UPS, but either way, the surge can demage the UPS before anything does it. I can't say if the MOVs inside UPS by reacting before the ones inside the surge protector would create some king of problem as well, but i think it would anyway. The coordination between the reaction of these MOVs is the main issue here.

Message was edited by: rau

[Anonymous user]

Hmmm, okay. It seems my PSU is Active PFC(>99%) and that according to the calculator, my setup consumes more or less 230w(are they serious? I'll just take this as a very rough estimate anyways).

You've lost me a bit at the 0.60 power factor part but I did manage to understand most of it anyways.

So, if my PSU is rated at >80% efficiency, then this means my efficiency is 80% and below?

Hmmm... I've got an MP130, a 2wire modem and a 2253lw monitor. Hmmm... looks like some calculating is due! ;D

[Anonymous user]

If your PSU is Active PFC > 99% it means its power factor can reach 0.99. The biggest power factor you can get from an applience is 1.

These figures are reached when the PSU is operating at 230-240V at 110-120V the PF is around 0.97-0.98, still very high.

For the 0.60 power factor, let me try to explain again.

The PSUs used in most electronics today ain't got power factor correction and by not having it the current (amperes) is never "running" "neck and neck" with the voltage, this is a peculiarity you can see in any SMPS, Switched Mode Power Supplies, and some electric motors. In the case of a SMPS, the PF or Power Factor, is about 0.60 or "60%". I know this is not very accurate, but if the PF is 60% theres is a lag of 40% between the current and voltage drawn and this causes more heating of wires, transformers, it can also cause some kind of distortions, the technical term for this is Harmonic Distortion. So, to cope with that without power factor correcting measures, the wires must have a higher gauge, the transformers must be bigger, etc. So, the exemple I gave you, of a 600VA transformer suppling power for a load which has a 0.6 power factor, this means the transformer is only capable of supplying 360 Watts, not 600Watts that it would be capable of if the power factor of the load were 1.

About the >80% efficiency, it means your PSU is 80 plus efficient or that it wastes 20% or less of all the power it is supplying at a given moment. 80+ PSUs for computers is the best thing you can get with today's technology.

Making a very rough estimation, I can say a 600VA UPS is what you need, but since APFC PSUs tend to draw all its rated power at the first milleseconds when when you turn it on, the UPS might get overloaded if more things are plugged to it at the same time other things are being turned on. So I advise you buying a bigger UPS just in case, something around 800VA or more. And it's not advisable running the UPS at full load. The unit will run hotter, the battery won't have enough juice for powering your computer for too long in case of power outages and the batteries might wear out faster because of the heat.

The estimates given by that calculator is said to be one of the most accurates, but its hard to fully trust it. The only way for knowing the exact numbers is measuring with specifc tools like an amperemeter, a Kill-a-watt or something like that.

I think a 600VA UPS would be enough for you, but I can't say for sure. What's an MP130?

Message was edited by: rau

[Anonymous user]

Right, I more or less got it now. 🙂

MP130 = Canon MP130 printer.

So, a 600VA unit would suffice for a home computer like mine, huh? 🙂

[Anonymous user]

According to my rough estimates, yes. But what is the codename of you Pentium 4 processor, northwood, prescott or galatin, how much RAM it got and how many RAM modules. I want to make my own calculation using the eXtreme Power Supply Calculator.

Your MP130 draws 42W which turns out to be 70VA since its Power factor is around 0.6.

Message was edited by: rau

Message was edited by: rau

[Anonymous user]

Processor:

P4 3.2ghz Cedar Mill D0
Ram: 2 x 1gb, DDR2-SDRAM PC2-5300 (333 MHz) - [DDR2-666]

Well, I won't be connecting the printer to the UPS since I rarely turn it on. Only the modem, Monitor and PC and maybe the external self-powered hdd will be on there. As for the external hdd, I no longer have the box and have been unable to find any information on the wattage the casing uses. I unscrewed the casing to check for labels but didn't find anything. I've been told, though, that the external hard disk will use just a few hundred mWatts since it's a usb connection.

Edit: Oh wait... found 1 page with info about this product. "Power Supply: Input 100~240V, Output 12V2A " <---- That's all I could find. 🙂

Message was edited by: Lucifiel

Message was edited by: Lucifiel

Message was edited by: Lucifiel

[Anonymous user · Accepted solution]

My calculations:


- Your computer: 261W @ Full Load.

Here it goes the calculations:

Calculating the efficiency losses which is 20% orless:

20% of 261W = 52,2W

52,2W + 261W = 313,2W will be drawn of the UPS.

An now calculating the power required in VA. Since you PSU has a 99% PF at 230/240V:

313,2W / 0.99 = 316VA

Total Consumption in VA: 316VA


Now the peripherals:

- Govibe + beyerDynamic: I think they pull out less than 12W since its USB powered right? But these two were used as input for the Extreme Calculator as 2 USB devices, so I'm not gonna count them here.


- MP130: 42W
- Monitor L2253: 45W
- External Hard Drive: about 25W max.
- 2wire 2701HGV-E - about 20W.

Total: 132W

And now I'm assuming the Power Factor of these equipments is about 0.6.

Total in VA: 132W / 0.6 = 220VA

316VA + 220VA = 536VA

Total power drawn of the UPS would be something around: 536VA at max.

This figure will only be reached if you use everything at the same time and at full load which is not likely to happen. For exemple, if you down the brigtness of your monitor, the power consumption can go from 45W to as low as 10W, depending on how much you decrease its contrast and brigtness. So a 600VA would be enough, but this would give you 4 to 5 minutes of power when on battery if 536VA is being drawn. It's most likely it will give you 10 minutes or more because as I said, you're almost never gonna be using everything at the same time and at full load.

If you're on a budget, buy the 600VA unit, if not, try to get a 750VA unit so as to have a bigger safety margin.