[ale] OT need 600-1000W power protection for 3 minutes - cheap

Wed Jul 10 12:23:32 EDT 2013

Wow, the third paragraph on mostly went right over my head. I realize you were responding to a post, but is that esoteric background or do I need to wrap my head around it to decide what size UPS I need. Coincidentally, we also need a new UPS and we're trying to figure out exactly what we need. I don't have a Kill-A-Watt, but I see I can pick one up for ~$20 if it'll help. The blurb on it claims: 

    * Large LCD display shows kW, volts, amps, watts, Hz and volt amps 

So how would I use that device, or another method, to size the correct UPS? And do I need to perform a calculation involving PI? 

Scott 
----- Original Message -----

From: "Alex Carver" <agcarver+ale at acarver.net> 
To: ale at ale.org 
Sent: Tuesday, July 9, 2013 12:45:45 PM 
Subject: Re: [ale] OT need 600-1000W power protection for 3 minutes - cheap 

I have three APC SmartUPS and have no problem whatsoever with apcupsd 
finding them. I get emails when the system goes on battery and the auto 
shutdown works fine across multiple machines with apcupsd sending data 
to other machines hanging off the same UPS running apcupsd in ethernet 
mode (no direct data connection to the UPS.) 

Here's your BR/BX explanation: http://forums.apc.com/message/23515 
The difference between the SMT and the BR/BX is the Smart Slot where you 
can add Smart Slot accessories like various management cards (ethernet) 
with temperature sensors, etc. Both the SMT and BR/BX have the normal 
USB/serial data port for connecting to a single computer. The Smart 
Slot just allows for direct ethernet connection and management by SNMP 
and APC's PowerChute software. 

Measuring in VA instead of W isn't marketing rubbish (entirely), it's 
proper engineering specification for AC circuits. Unless your voltage 
and current are exactly in phase at all times with no distortions at 
all, Watts are meaningless unless you also specify VAr or the power 
factor. Volt-Amps eliminates the need for the power factor because it 
represents the scalar length of the power phasor (vector) regardless of 
where it's pointing in W/VAr space (the 2pi radian range of phase angle.) 

Using volt-amps for the specification means that a power supply (the UPS 
in this case) can supply varying types of loads with different power 
factors and the total available apparent power (real and 
reactive/imaginary) is constant. A 100 VA motor and a 100 VA light bulb 
require the same amount of apparent power. The light bulb needs mostly 
real power and the motor needs mostly reactive power. 

Where the marketing comes in is the fact that the engineers are forced 
(by marketing drones) to pick an average power factor so they can label 
the object. Typical switching supplies (prior to a concerted push 
against manufacturers by power companies to make them electrically 
cleaner) have a power factor of 0.6-0.8 and some really crappy Chinese 
knock-offs have power factors down near 0.4 with hideous harmonics. APC 
assumes a power factor of somewhere around 0.65 for connected devices 
which is why your Watt rating is lower because some of the available VA 
must be used for the VAr portion of the load demand. 

On 7/9/2013 08:45, Ron Frazier (ALE) wrote: 

> Hi all, 
> 
> To be honest, I need to save some money for this project, since, when 
> spending $ 200 at a time, and multiple times, it adds up. But, I hope 
> to implement it soon. I might be able to buy one new unit, and reduce 
> the load on one pc to use my old ups with that. Not sure yet. 
> 
> The more I think about my loads, the more I think I need a 1500 VA / ~ 
> 900W unit. A 1200VA/~700W unit might do it, but most product lines seem 
> to jump to 1500 VA after 1000 VA. 
> 
> The last time I bought a UPS, it was from Frys. I have no complaints, 
> but you do pay sales tax and probably an intrinsically higher price. The 
> advantage is easier returns if needed. I can't believe it, but I am 
> actually considering mail ordering a UPS. I understand from Amazon 
> reviews on some, that you have to pay to ship it back to the factory if 
> there is a problem, which can be expensive. 
> 
> Based on prior discussions and my experience, I know APC is a good 
> brand. I also understand that, for the "smart" units, it can be hard to 
> get linux to talk to it, if you want to use the auto shutdown software 
> like apcupsd. I think you guys told me before that Tripplite is good, 
> so I may look at those. Based on some amazon reviews and prior comments 
> here, it sounds like I should stay away from Cyberpower. 
> 
> I think it's total marketing rubbish that they rate these things by VA 
> primarily. My computer is currently pulling 539 VA and 532 W, according 
> to the Kill-A-Watt EZ, with a power factor of .98. The UPS I have is an 
> SMT-750 so you would think it could handle the load. But NO, that's 750 
> VA. The watts are limited to 500, so the thing yells like crazy if I 
> run this load on it. (So I don't.) So, it should be labeled SMT-500! 
> That unit was capable of handling the load before I upped the load. Yes, 
> I do know what VA means. It's just difficult to remember to cut 
> whatever number I see on the box almost in half to get a realistic load. 
> 
> Charles, thanks for the links. I'll keep the buy batteries local idea 
> in mind. Might not be necessary with Amazon's free shipping. 
> 
> It's nice to see that the major makers are starting to come out with 
> some bigger units, with some smarts, with more reasonable price tags. 
> 
> That Fry's link you posted is actually quite interesting. I found it's 
> bigger brother on Amazon. 
> 
> http://www.amazon.com/APC-BR1500G-BACK-UPS-10-Outlet-1500VA/dp/B003Y24DEU/ref=sr_1_1?s=electronics&ie=UTF8&qid=1373381258&sr=1-1&keywords=br1500g 
> 
> 
> APC's different model numbers are confusing. For example, I don't know 
> the difference between a BR and a BX unit. 
> 
> This unit is a 1500 VA / 865 W unit, with lcd (or led or something) 
> status display, and AVR (automatic voltage regulation [very cool]); for 
> $ 179 with free shipping and no sales tax. This unit has a BR part number. 
> 
> This is at a price point / capacity point that's really starting to get 
> my attention. 
> 
> Here's a similar unit at Frys. 
> 
> http://www.frys.com/product/5955004?site=sr:SEARCH:MAIN_RSLT_PG 
> 
> It has a BX part number. Go figure. The capacity is the same, but it's 
> $ 210, or $ 225 after sales tax. 
> 
> In any case, much better than the $ 500 Frys wants for the SMT-1500. So, 
> I guess the big question is, what do I give up by going with the BR/BG 
> 1500 and saving $ 300 versus the SMT-1500? I'll have to do some 
> research on that. 
> 
> Alex, good point about the cooling. If I'm using a stock battery and a 
> name brand, it will probably be ok. If I'm using a non standard 
> battery, that may be something I have to look at. 
> 

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