On Tue, 20 Sep 2011 17:14:15 +0100, "Johny B Good"   
    wrote:   
      
   >On Tue, 20 Sep 2011 13:31:15 +0100, Jim Wilkins    
   >wrote:   
   >   
   >>   
   >> "Bob F"  wrote in message   
   >> news:j58nbe$aqt$1@dont-email.me...   
   >>> I just unplugged the Belkin 1200 VA UPS powering my computer, and   
   >>> plugged   
   >>> it into my Kill-o-watt meter. After the UPS quit beeping after power was   
   >>> restored, the meter shows 7-11 watts being consumed by the UPS feeding   
   >>> the   
   >>> computer, which is way less than the computer (quad core core-duo   
   >>> processor) uses.   
   >>>   
   >>> Does the killowatt have a problem reading accurately with UPS units?   
   >>   
   >> I just checked a KAW P4400 with two stepped square wave inverters and a   
   >> 60W   
   >> incandescent lamp. It shows 111V 55W and 129V 59W. I see odd readings on   
   >> the   
   >> input of a UPS too, but they have always been higher than expected.   
   >>   
   >   
   >  When you say higher than expected, do you mean, for example in the case   
   >of an APC SmartUPS 700, higher than the expected 20W maintenance load   
   >(fully charged battery, or, indeed, no battery at all)[1] plus the load,   
   >say 100W, giving a reading higher than the expected sum total figure of   
   >120W?   
   >   
   >  I must admit that I haven't made such measurements to check on how much   
   >greater the cost of supplying a PC with mains power is over and above the   
   >simple no load maintenance power draw of the UPS in question (when its   
   >battery is fully charged) plus load wattage. I suppose there could be a   
   >small additional loss on top of the no load maintenance 'loss' when a load   
   >is drawing current through the filtering circuitry of the UPS but I would   
   >have expected this to be an insignificant loss unless the UPS was equipped   
   >with a buck/boost transformer function to avoid transferring to battery   
   >power during modest sags and dips and it happened to be correcting for a   
   >sag in line voltage at the time.   
   >   
   >[1] The maintenance load figure is the one item that the UPS manufacturers   
   >seem to be extremely reluctant to actually include in their   
   >specifications. It's a figure I've never been able to find in _any_ UPS   
   >published specifications that I have looked at (and I've perused quite   
   >few).   
   >   
   >  I suppose this is an inherited 'Mind Set' harking back to the days of   
   >cheap power but those days have long since passed into history. Now that   
   >the cost of power is a much greater factor, not just to the home user but   
   >also to large data centres where they can be using several hundred KWH per   
   >day, it is rather surprising that the UPS manufacturers are still treating   
   >the maintenance figure as a 'dirty little secret' never to be openly   
   >disclosed to their customers.   
   >   
   >  FYI, I can give you maintenance figures for the following APC units that   
   >I own:   
   >   
   >  SmartUPS 2000		32 to 35 watts   
   >  SmartUPS 700		20 watts exactly   
   >  Backups 500		3 watts   
   >   
   >  In all cases, this is the power drawn when their respective batteries are   
   >in the fully charged condition (which, in the case of the SmartUPS 700 is   
   >the same as with the battery disconnected - it supports hot swapping of   
   >its battery pack).   
   >   
   >  The measurements were all made using a Metrawatt analogue wattmeter set   
   >to the 100v and 1A range settings (100 watt FSD range) on a 240v 50Hz UK   
   >supply voltage. The 100v setting might seem an odd choice for a 240v   
   >supply but I wanted to measure on the lowest range scale possible and the   
   >moving coil part of the circuit has no iron to saturate and will typically   
   >be capable of coping with a tenfold overload without risk of burnout   
   >(although the multiplier resistor may not be so lucky with _that_ level of   
   >overload). It has coped quite nicely with the 20% overload over and above   
   >the built in factor of two limit for the selected voltage range during the   
   >last 15 years or so of 24/7 connection to the 240v mains supply.   
   >   
   >HTH & HAND   
      
      
   I've got a fully charged Powereware Prestige 1000 va online UPS   
   sitting on my "Kill-a-watt" type unit right now, and it is fluctuating   
   between 0 and 61 watts, constantly changing. On the AMPS range, it is   
   pretty steady at 0.72 to 0.73 amps - which at unity power factor would   
   be 84 watts (117 volt line voltage) and there is NO WAY it is   
   dissipating 84 watts (or even 62) of power as heat. The unit isn't 2   
   dgrees F above ambient, and it's been running for several weeks.   
      
   I suspect there is some strangeness in the power factor throwing the   
   unit off.   
      
   Putting a hologen lamp on the kill-a-watt it reads 266 watts - plugged   
   into the UPS, it reads 339 to 334 - which would indicate the   
   "overhead" of the UPS is ABOUT 70 - 75 watts.   
      
   Again, I'm SURE it is reading considerably high - but the fluctuation   
   is significantly less than when it is running at no load. a 40 watt   
   bulb in the case would make it SIGNIFICANTLY hotter than the operating   
   UPS.   
      
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