[crmhu]

I have a new desktop computer that I am using in a location where the electricity goes down from time to time, usually from a few seconds to a few minutes. I am looking for information about what specs I need in a UPS in order to keep constant voltage, but I am finding confusing information about sine waves, etc. Can someone please advise me? Here's the information about my computer:

Dell XPS 8300
Intel® Core™ i7-2600 CPU @ 3.40GHz 8MB Cache
16.0 GB DDR3 SDRAM, 1333MHZ, 4X4GB
Dell Monitor 21.5 Inch Wide, ST2220LB
AMD Radeon HD 6770
1.5TB Serial ATA 2 HD 7200 RPM
Blu-ray 8X BD-R, DVD+/-RW Drive with DVD+R double layer write capability
Dell 1520 WLAN PCIe card with11n mini-Card and internal antenna
Windows 7 Professional 64-bit
Service Pack 1

I also have a Samsung Story Station 1TB USB external hard drive that I want to protect, too.

Thanks!
CRMHU

[mjd420nova]

First, I didn't see a power supply spec so I can give you a general parameter range. If the wattage needed , lets say 500 watts, the next factor is how long you want the units to run under full power. Most UPS ratings are about the same as battery power, Volt Amperature Hour (VAH). Or some try to confuse by using MVAH, millivoltamp hour. The time needed to run under backup is lets say 30 minutes. So if ( half hour) times 500 equals 250 VAH. Confused yet?? Working with whole hours makes it easier. Now toss in the monitor wattage and don't forget the modem, router and whatever else you might need to protect, as that's the main idea, protection. Many units (the cheaper ones) do a poor job of replicating a sine wave to supply the voltage under load. I suspect that a smaller 750 VAH rating would suffice for just about any installation unless there are servers or other critical units that will not tolerate an unscheduled shut down. I use two smaller ones, 650 VAH each, one for a server just by itself and the other for modem, router and the big LCD TV with satelite box. Insure you have adequate ground from the supply outlet and try not to use a power strip plugged into a power strip for larger installs. Units need exercise and a user manual will give you the procedure for that.

[crmhu]

mjd420nova, on 28 July 2012 - 10:39 AM, said:

First, I didn't see a power supply spec so I can give you a general parameter range. If the wattage needed , lets say 500 watts, the next factor is how long you want the units to run under full power. Most UPS ratings are about the same as battery power, Volt Amperature Hour (VAH). Or some try to confuse by using MVAH, millivoltamp hour. The time needed to run under backup is lets say 30 minutes. So if ( half hour) times 500 equals 250 VAH. Confused yet?? Working with whole hours makes it easier. Now toss in the monitor wattage and don't forget the modem, router and whatever else you might need to protect, as that's the main idea, protection. Many units (the cheaper ones) do a poor job of replicating a sine wave to supply the voltage under load. I suspect that a smaller 750 VAH rating would suffice for just about any installation unless there are servers or other critical units that will not tolerate an unscheduled shut down. I use two smaller ones, 650 VAH each, one for a server just by itself and the other for modem, router and the big LCD TV with satelite box. Insure you have adequate ground from the supply outlet and try not to use a power strip plugged into a power strip for larger installs. Units need exercise and a user manual will give you the procedure for that.

Wow, that's a lot to absorb! Thanks for all the information, mjd420nova; I appreciate your expertise.

crmhu

[waldojim]

One thing MJD didn't cover is "online" VS "Standby" UPS. If you have frequent trouble with power, and need to maintain proper power during brown-outs as well as complete loss, you may want to consider moving to an online UPS. This way, you are always on clean power, and there are no momentary power drops while the system switches to the batteries. This will results in longer life for your PC. The problem is that these systems are more expensive, and may require more frequent battery changes.

[mjd420nova]

WJ: I didn't mention those units as you stated, they are expensive and difficult to maintain. These are the types you'll find in industrial sizes and application. Like a CV transformer, they consume large amounts of power, even when idle. The "whole house" solution would be more practical but systems are best installed during primary construction. I used to maintain a clients facility with 56, 12 KVAH units. Needless to say it was a huge undertaking but battery maintenence was a breeze when they used the big glass walled batteries. Easy to see what's happening. Home units will seldom be more than 1500 VAH. Response times are pretty tight, something like a tenth of a cycle so you shouldn't notice or even detect any switch over. Reliablity is directly proportional to the price you pay. ANother problem is the improper grounding and mixing non-polarized units plugged into a UPS outlets. Some strange things have happened when grounded units on one side of the line gets mixed with the ground, neutral and hot sizes on devices grounded through a UPS. Interconnecting cables can link devices and create ground loops that can start fires and even eletrocute.

[MLStrand56]

crmhu, on 28 July 2012 - 08:56 AM, said:

I have a new desktop computer that I am using in a location where the electricity goes down from time to time, usually from a few seconds to a few minutes. I am looking for information about what specs I need in a UPS in order to keep constant voltage, but I am finding confusing information about sine waves, etc. Can someone please advise me? Here's the information about my computer:


CRMHU

APC has a Free publication that explains various UPS designs. Some will adj. their output voltage during Brown-Outs.

I live in Philippines & Brown-Outs are Extremely Frequent here (as are Black-Outs). I run a 1000 Watt AVR (Automatic Voltage Regulator) to power all my computer equipment. It's motor driven & automatically increases the output AC voltage, when the input AC power sags.

MLStrand56