Converting Watts To Amps And Vice Versa

peripherals, and need help on how to convert between amps and volts, and vice versa, so I know what size UPS to get. Here is what I got from all the peripherals:

Did you mean "Uninterruptible Power Supply" ?

Sylvia.

"Dave Henning"

** Surely you mean an " Un-interruptible Power Supply" ?? ** I reckon a 300 watt job should do you.

Go for a 500 watt if you want to be very safe.

Remember, it will only run the gear for a few minutes in either case.

..... Phil

Yes I did mean "uninterruptible", no idea where "universal" came from ;). Think I'll try and seek out a 500 watt one. Thanks.

Dave Henning wrote: You want to know your total watts

+120W

_Probably 12V, so +18W, say 20w for ease

+85W

+80W (actually less, but shrug)

+85W

+8W

Say 400w Is your power requirement.

Doesn't make sense

Apologies. I misread the initial post.................

This would be the minimum you need to buy.

You can go higher than this, as this will give you longer running time if the power fails, even with a smaller load than the rating of the UPS It also provides some headroom in case you add more devices to it later on.

For example I have a 1600va UPS on my system, for the reason is that this longer running time will keep the ADSL modem on for 2 hours or so, this allows use of the internet via the laptop (run from its own battery) and the VOIP phone for blackouts that happen during work hours when you need to have these things online. A 8w CFL can be run from it as well and will run for some time if the power fails at night.

If you need longer run times than this, or want to run higher powered devices, it would be time to look at a generator.

I don't need to run devices of the battery very long, just long enough to s= afely shut my Macs down, to prevent hard drive damage. I'm currently looki= ng at this one,

**Unless you have an extremely ancient Mac, hard drive damage due to a power failure is incredibly unlikely. All hard drives manufactured in the last 20 years operate using a system where the heads retract under power down conditions. This is a mechanical operation and thus unencumbered by power loss. Prior to modern hard drives, we used stepper motor drives in cheaper systems, where damage was possible, if the heads were not 'parked' under power down conditions.

The real reason for using a UPS, is so you can save your work, or so the operating system does not run into problems when premature shut down occurs. I'm not a Mac user, so I don't know much about the things (other than that they are slow and frustrating to use, but ever since Windows XP, shutting down Windows prematurely has not been a problem. I guess Macs are not as sophisticated. Macs appear to be style over substance.

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Trevor Wilson
www.rageaudio.com.au

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True, I haven't seen a drive that needed parking since the early

1990's, and even then it MIGHT not really have needed it, but we played it safe.

IIRC, at power off, the rotational inertia of the platters is sufficient to allow the platter motor to generate enough power to ensure the heads get safely parked.

Haven't used or seen a Mac. Many seem to rave about them for some reason, I have no idea what is good about them over a PC, unless they are needed for specific tasks or industry, or is it just a MS bashing exercise / status symbol of some kind ?.

While not relevant to the situation you describe,

I have had problems with hard drives giving problems when the power supply is overloaded that probably should be taken into account when choosing a UPS.

Symptoms were: one drive would run hot and may "click" like it is at the end of its life. Other drive will be fine. Drives worked fine in my computer, which had a 500w supply at the time.

After a lot of confusion over this problem, removing the Antec power supply, fitting a larger capacity generic power supply fixed the problem. I have heard of other problems involving past Antec supplies, but this one took the cake. The computer shop where we bought our parts had seen this several times, and it was their advice that solved the problem.

This year I saw a similar case where a guy had 6 hard drives in his PC and the power supply wasn't big enough. Really weird problems including Drives randomly "disappearing" from "my computer" and this would sometimes rearrange the drive letter, and/or not be able to find the boot drive at restart as well as the problem mentioned above. Some programs or files wouldnt work or be located properly as the letters had changed.

Advised him to either get a massive power supply, & add extra fans to get rid of the heat, and wear the extra power bill or get a 1.5TB and dump the old 2-300g units. He chose option #2 and dumped the old drives on Ebay. This fixed the problem and dropped the case temperature substantially.

Another thing I notice is that many of these "high wattage" supplies may have substantial stated amperage on various rails, but with most of them, the wire gauge looks inadequate to deliver this current to the devices without a lot of loss. About the only exception I have seen in the low cost range was the AC BEL "tru power" unit

Err, Watts has no time parameter.

Well, UPS's are really just a device for elegant, but immediate shutdowns, or if you are really serious, to fill in till the generator kicks in. However the number of people who take this on board is infinitesimal.

Some of us use largish ups's say 3500 watts plus a squad of external batteries tobesure tobesure

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X-No-Archive: Yes

Many are the occasions when we've had power glitches long enough to cause a PC to reboot, but for our UPS.

Sylvia.

I don't know what your (or anyone elses) environment is like, but isn't a UPS a bit like bottled water in many cases, ie. the normal reticulated utility is good enough in practice? Sure, for a business full of critical servers it's a nobrainer, but in a home environment, what's the impact of the occasional power brownout?

Me and most of the other people I know have run many computers and related devices for many years directly on the raw mains, and never had a significant problem.

Perhaps some places are more prone to glitches than others.

Prior to installing a UPS, I certainly had computers reset as a result of power glitches, and lost work in the process - OK, not much work, but some. I can't say how often, but I can say they were annoying when they happened.

Sylvia.

The point I was making is that a significantly larger VA rated UPS will have larger capacity batteries, and therefore will run for longer on the same load. Also if you lower the current drawn from the battery, it lasts much longer.

If you are drawing 400w from a 12v battery (typically 6-7AH in these units) that is a load of 33.3 A In the 1600va unit I use, there are 2 series 7AH batteries. This will result in 16.6A load @ 24v

IF you look at the table on page 22 of this manual from a previous UPS post, you can see that by halving the current drawn from the batteries, there are enormous increases in running time - from 100% load to 50% load for example, the time you can run the UPS quadruples. Halving the load at lower percentages has less of an effect - but it still gives you more than double the run time.

You could put a much larger battery on a small UPS unit, but it will probably take forever to charge, the inbuilt charger might not like it, heatsinking and ventilation of the UPS might only be adequate for the amount of time a given load can expect to be powered by specified battery, not for significantly longer periods that a much larger battery would provide.

For the case I mentioned where you want to keep a small load online like the ADSL modem / VOIP, 2+ hours is possible with my setup. A generator is overkill.

Commercial or critical setups are a different story.

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Where I am, the 11kv lines go out of town for about 30km, much of which there are lots of trees nearby, and even goes under the sea to an island. Because of this, any time there is a decent summer storm or strong wind that blows stuff around or branches go flying, we lose power at the drop of a hat, or cop brief but damaging dropouts.

On the PC I had from about 2004-6 these "dropouts" would instantly power off the PC, and in some cases, it would not turn on again unless you turned the mains off for 10min. Other times the power supply would simply refuse to turn on at all, and had to be "forced" on by momentarily grounding the power on (green wire) in the ATX plug to the motherboard. After this it would again work fine.

When you have several of these losses in one night, it gets very irritating, especially if the power might only be off for seconds or a couple of minutes. A UPS with substantial capacity will tide you over no problems, I have not been without it since, and have had no more of these problems. Has saved me a lot of time and effort, and probably helped avoid PC damage that costs a lot in downtime and inconvenience. "Dirty" power like this is another reason to have a good UPS.

We also have people we do work for who are in remote areas on SWER lines. UPS are a godsend here, especially the ones that can switch the output mains voltage up and down as the incoming line voltage changes.

Wouldn't just turning on autosave be a cheaper solution? Works for me anyway.

MrT.

I have fixed quite a few computers with bricked m/b (power went off/power glitch during BIOS upgrade) and stuffed Windows (power went off/power glitch during updates or new driver install). By default Windows reboots on blue screen so second scenario usually produces endless loop of booting up, blue screen (not long enough to read), reboot, blue screen... thanks Microsoft!

Tom