Pure Sine Wave UPSes for New Dell PCs
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From: William R. Walsh on 9 Apr 2010 13:16 Hi! > It's probably impossible to come up with accurate measurements > for the actual inrush current and minimum transfer time of a > given power supply. The general rule is to multiply the current rating printed on the nameplate by three. That's your inrush current figure. As that rating is frequently a worst case rating, for a fully loaded machine doing everything at once, you'll have some headroom here. If you could find a meter with a sufficiently fast response time with a "peak hold" function, that could be used to figure it out at as well. A UPS is seldom if ever going to be powering your system from a true cold start (where inrush current would be an issue). Every ATX power supply I have ever seen keeps a small portion of its circuitry alive when plugged in (and the switch at the back, if there is one, turned on). The main filter capacitors are also usually kept charged in this case. So you really only have to be concerned about the average amount of power your system is using. There are inexpensive plug in meters that can tell you all of this quickly and easily. Most have multiple scales of measurement (watts, amps, line voltage, volt amps) that are reasonably accurate. The P3 Kill-A-Watt is one such meter, and it is readily available. One of these can be a very worthwhile investment. Then figure about 20-30% headroom on top of that for your UPS capacity. The way I'd do it is to plug everything into the meter, power up all the equipment you want the UPS to protect, do something that runs your CPU usage up to 100% for a few minutes You should test your UPS periodically. Better units have a button to press for testing (a feature curiously absent from the plug strip types sold by APC, Tripp-Lite and Cyber Power) and even better units conduct timed self tests on a repeating schedule (usually every two weeks). Those that don't have a dedicated "push to test" button can sometimes be tested by pressing and holding the power button for a few seconds. Although I have never had a problem doing so, pulling the plug on your UPS to test it can result in the grounds for each piece of computing equipment entering a "floating" state. This does assume that the grounds are properly connected when the UPS is plugged in, as they should be. (This means that if your UPS has its "site wiring fault" light on, you need to find out why and have the problem fixed.) However, it is a guaranteed test. William
From: William R. Walsh on 9 Apr 2010 13:23 Hi! (oops!) > The way I'd do it is to plug everything into the meter, power up > all the equipment you want the UPS to protect, do something > that runs your CPU usage up to 100% for a few minutes ...., turn on all peripheral devices and take a reading with your meter set to report volt-amps (because that's how UPS units are rated). Don't put your printer on the UPS. Although inkjet printers are unlikely to cause trouble, laser printers will. The fuser demands an enormous inrush current whenever it fires, and this will overwhelm the inverter in all but the very largest UPS units, causing it to shut down (best case) or fail in an exciting way. William
From: Al Dykes on 9 Apr 2010 13:38 In article <b0fe48c9-4817-45fb-b018-7886da81b457(a)u22g2000yqf.googlegroups.com>, William R. Walsh <wm_walsh(a)hotmail.com> wrote: >Hi! >on). The main filter capacitors are also usually kept charged in this >case. So you really only have to be concerned about the average amount >of power your system is using. > >There are inexpensive plug in meters that can tell you all of this >quickly and easily. I think you are deescribing the"Kill-A-Watt". http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU >seconds. > >Although I have never had a problem doing so, pulling the plug on your >UPS to test it can result in the grounds for each piece of computing >equipment entering a "floating" state. This does assume that the >grounds are properly connected when the UPS is plugged in, as they >should be. (This means that if your UPS has its "site wiring fault" >light on, you need to find out why and have the problem fixed.) >However, it is a guaranteed test. I know of a case where a UPS wouldn't supply juice if it wasn't plugged into the utility mains. It was a "field day" exercise and the intent was to power a WiFi repeater off the grid. -- Al Dykes News is something someone wants to suppress, everything else is advertising. - Lord Northcliffe, publisher of the Daily Mail
From: Daddy on 9 Apr 2010 14:20 William R. Walsh wrote: > Hi! > >> It's probably impossible to come up with accurate measurements >> for the actual inrush current and minimum transfer time of a >> given power supply. > > The general rule is to multiply the current rating printed on the > nameplate by three. That's your inrush current figure. As that rating > is frequently a worst case rating, for a fully loaded machine doing > everything at once, you'll have some headroom here. > > If you could find a meter with a sufficiently fast response time with > a "peak hold" function, that could be used to figure it out at as > well. > > A UPS is seldom if ever going to be powering your system from a true > cold start (where inrush current would be an issue). Every ATX power > supply I have ever seen keeps a small portion of its circuitry alive > when plugged in (and the switch at the back, if there is one, turned > on). The main filter capacitors are also usually kept charged in this > case. So you really only have to be concerned about the average amount > of power your system is using. > > There are inexpensive plug in meters that can tell you all of this > quickly and easily. Most have multiple scales of measurement (watts, > amps, line voltage, volt amps) that are reasonably accurate. The P3 > Kill-A-Watt is one such meter, and it is readily available. One of > these can be a very worthwhile investment. Then figure about 20-30% > headroom on top of that for your UPS capacity. > > The way I'd do it is to plug everything into the meter, power up all > the equipment you want the UPS to protect, do something that runs your > CPU usage up to 100% for a few minutes > > You should test your UPS periodically. Better units have a button to > press for testing (a feature curiously absent from the plug strip > types sold by APC, Tripp-Lite and Cyber Power) and even better units > conduct timed self tests on a repeating schedule (usually every two > weeks). Those that don't have a dedicated "push to test" button can > sometimes be tested by pressing and holding the power button for a few > seconds. > > Although I have never had a problem doing so, pulling the plug on your > UPS to test it can result in the grounds for each piece of computing > equipment entering a "floating" state. This does assume that the > grounds are properly connected when the UPS is plugged in, as they > should be. (This means that if your UPS has its "site wiring fault" > light on, you need to find out why and have the problem fixed.) > However, it is a guaranteed test. > > William I have learned several things from this entire exercise: 1- Dell technical support reps don't know what a PFC power supply is, and aren't sure whether any Dell computer has one. 2- Dell technical support reps don't really understand the published specifications for the computers they are supporting. 3- None of the big UPS makers will come out and say: You can't use our home and small office UPSes if your computer has a PFC power supply. 4- None of the formulas, online calculators or techniques to calculate or estimate the correct size UPS for your computer arrive at the same conclusion. 5- Nobody agrees on the correct method to calculate or estimate the correct size UPS. 6- No OEM will tell you: If you are thinking about purchasing this particular computer, consider this: It will require a UPS that will cost you half as much as the computer itself for adequate power protection. 7- No UPS maker will say whether they'll honor their warranty if you use a stepped approximation unit with a PFC power supply. I apologize for ranting. Daddy
From: RnR on 9 Apr 2010 14:38
On Fri, 09 Apr 2010 14:20:53 -0400, Daddy <daddy(a)invalid.invalid> wrote: >William R. Walsh wrote: >> Hi! >> >>> It's probably impossible to come up with accurate measurements >>> for the actual inrush current and minimum transfer time of a >>> given power supply. >> >> The general rule is to multiply the current rating printed on the >> nameplate by three. That's your inrush current figure. As that rating >> is frequently a worst case rating, for a fully loaded machine doing >> everything at once, you'll have some headroom here. >> >> If you could find a meter with a sufficiently fast response time with >> a "peak hold" function, that could be used to figure it out at as >> well. >> >> A UPS is seldom if ever going to be powering your system from a true >> cold start (where inrush current would be an issue). Every ATX power >> supply I have ever seen keeps a small portion of its circuitry alive >> when plugged in (and the switch at the back, if there is one, turned >> on). The main filter capacitors are also usually kept charged in this >> case. So you really only have to be concerned about the average amount >> of power your system is using. >> >> There are inexpensive plug in meters that can tell you all of this >> quickly and easily. Most have multiple scales of measurement (watts, >> amps, line voltage, volt amps) that are reasonably accurate. The P3 >> Kill-A-Watt is one such meter, and it is readily available. One of >> these can be a very worthwhile investment. Then figure about 20-30% >> headroom on top of that for your UPS capacity. >> >> The way I'd do it is to plug everything into the meter, power up all >> the equipment you want the UPS to protect, do something that runs your >> CPU usage up to 100% for a few minutes >> >> You should test your UPS periodically. Better units have a button to >> press for testing (a feature curiously absent from the plug strip >> types sold by APC, Tripp-Lite and Cyber Power) and even better units >> conduct timed self tests on a repeating schedule (usually every two >> weeks). Those that don't have a dedicated "push to test" button can >> sometimes be tested by pressing and holding the power button for a few >> seconds. >> >> Although I have never had a problem doing so, pulling the plug on your >> UPS to test it can result in the grounds for each piece of computing >> equipment entering a "floating" state. This does assume that the >> grounds are properly connected when the UPS is plugged in, as they >> should be. (This means that if your UPS has its "site wiring fault" >> light on, you need to find out why and have the problem fixed.) >> However, it is a guaranteed test. >> >> William > >I have learned several things from this entire exercise: > >1- Dell technical support reps don't know what a PFC power supply is, >and aren't sure whether any Dell computer has one. > >2- Dell technical support reps don't really understand the published >specifications for the computers they are supporting. > >3- None of the big UPS makers will come out and say: You can't use our >home and small office UPSes if your computer has a PFC power supply. > >4- None of the formulas, online calculators or techniques to calculate >or estimate the correct size UPS for your computer arrive at the same >conclusion. > >5- Nobody agrees on the correct method to calculate or estimate the >correct size UPS. > >6- No OEM will tell you: If you are thinking about purchasing this >particular computer, consider this: It will require a UPS that will cost >you half as much as the computer itself for adequate power protection. > >7- No UPS maker will say whether they'll honor their warranty if you use >a stepped approximation unit with a PFC power supply. > >I apologize for ranting. > >Daddy Don't apologize.... this post taught me something <grin>. |