Converting Watts To Amps And Vice Versa

[Dave Henning]

I'm looking at buying a Universal Power Supply for my computer and related 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:

iMac 2.5-1.25 A, 120 W
LCD Display 1.5 A
Mac Mini 85W
External Hard Drive .65A 51-80VA
Amp 85W
Lamp 8W, 80 mA

Can anyone tell me how all this watts, volts, amps conversion works? All it gives me is confusion.

 

[Sylvia Else]

On 28/12/2010 2:10 PM, Dave Henning wrote:

I'm looking at buying a Universal Power Supply for my computer and related 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.

 

[Phil Allison]

"Dave Henning"

I'm looking at buying a Universal Power Supply

** Surely you mean an " Un-interruptible Power Supply" ??

for my computer and related 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:

iMac 2.5-1.25 A, 120 W
LCD Display 1.5 A
Mac Mini 85W
External Hard Drive .65A 51-80VA
Amp 85W
Lamp 8W, 80 mA

Can anyone tell me how all this watts, volts, amps conversion works?
All it gives me is confusion.

** 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

 

[terryc]

Dave Henning wrote:
You want to know your total watts

iMac 2.5-1.25 A, 120 W
+120W

LCD Display 1.5 A
_Probably 12V, so +18W, say 20w for ease

Mac Mini 85W
+85W

External Hard Drive .65A 51-80VA
+80W (actually less, but shrug)

Amp 85W
+85W

Lamp 8W, 80 mA
+8W

Say 400w
Is your power requirement.

 

[Dave Henning]

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

 

[Metro]

"terryc" <newsninespam-spam@woa.com.au> wrote in message
news:ifc7mv$b6m$1@news.eternal-september.org...

Dave Henning wrote:
You want to know your total watts

iMac 2.5-1.25 A, 120 W
+120W

LCD Display 1.5 A
_Probably 12V, so +18W, say 20w for ease

Mac Mini 85W
+85W

External Hard Drive .65A 51-80VA
+80W (actually less, but shrug)

Amp 85W
+85W

Lamp 8W, 80 mA
+8W


Say 400w
Is your power requirement.

Doesn't make sense

 

[Metro]

"Metro" <Home@home> wrote in message
news:4d1a6808$0$3428$afc38c87@news.optusnet.com.au...

"terryc" <newsninespam-spam@woa.com.au> wrote in message
news:ifc7mv$b6m$1@news.eternal-september.org...
Dave Henning wrote:
You want to know your total watts

iMac 2.5-1.25 A, 120 W
+120W

LCD Display 1.5 A
_Probably 12V, so +18W, say 20w for ease

Mac Mini 85W
+85W

External Hard Drive .65A 51-80VA
+80W (actually less, but shrug)

Amp 85W
+85W

Lamp 8W, 80 mA
+8W


Say 400w
Is your power requirement.

Doesn't make sense
Apologies. I misread the initial post.................

 

[kreed]

On Dec 28, 6:38 pm, terryc <newsninespam-s...@woa.com.au> wrote:

Dave Henning wrote:

You want to know your total watts

iMac 2.5-1.25 A, 120 W

+120W

LCD Display 1.5 A

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

Mac Mini 85W

+85W

External Hard Drive .65A 51-80VA

+80W (actually less, but shrug)

Amp 85W

+85W

Lamp 8W, 80 mA

+8W

Say 400w
Is your power requirement.

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.

 

[Dave Henning]

I don't need to run devices of the battery very long, just long enough to safely shut my Macs down, to prevent hard drive damage. I'm currently looking at this one, http://www.apc.com/products/resource/include/techspec_index..cfm?base_sku=BE700G-AZ&total_watts=200

 

[Trevor Wilson]

Dave Henning wrote:

I don't need to run devices of the battery very long, just long
enough to safely shut my Macs down, to prevent hard drive damage.
I'm currently looking at this one,
http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=BE700G-AZ&total_watts=200

**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.


--
Trevor Wilson
www.rageaudio.com.au

 

[kreed]

On Dec 29, 3:49 pm, "Trevor Wilson" <tre...@rageaudio.com.au> wrote:

Dave Henning wrote:
I don't need to run devices of the battery very long, just long
enough to safely shut my Macs down, to prevent hard drive damage.
I'm currently looking at this one,
http://www.apc.com/products/resource/include/techspec_index.cfm?base_...

**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.

--
Trevor Wilsonwww.rageaudio.com.au

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

 

[terryc]

kreed wrote:

On Dec 28, 6:38 pm, terryc <newsninespam-s...@woa.com.au> wrote:
Dave Henning wrote:

You want to know your total watts

iMac 2.5-1.25 A, 120 W
+120W

LCD Display 1.5 A
_Probably 12V, so +18W, say 20w for ease

Mac Mini 85W
+85W

External Hard Drive .65A 51-80VA
+80W (actually less, but shrug)

Amp 85W
+85W

Lamp 8W, 80 mA
+8W

Say 400w
Is your power requirement.

This would be the minimum you need to buy.

Err, Watts has no time parameter.

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.

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.

 

[atec77]

On 29/12/2010 10:45 PM, terryc wrote:

kreed wrote:
On Dec 28, 6:38 pm, terryc <newsninespam-s...@woa.com.au> wrote:
Dave Henning wrote:

You want to know your total watts

iMac 2.5-1.25 A, 120 W
+120W

LCD Display 1.5 A
_Probably 12V, so +18W, say 20w for ease

Mac Mini 85W
+85W

External Hard Drive .65A 51-80VA
+80W (actually less, but shrug)

Amp 85W
+85W

Lamp 8W, 80 mA
+8W

Say 400w
Is your power requirement.

This would be the minimum you need to buy.

Err, Watts has no time parameter.


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.

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

--
X-No-Archive: Yes

 

[Sylvia Else]

On 29/12/2010 11:45 PM, terryc wrote:

kreed wrote:
On Dec 28, 6:38 pm, terryc <newsninespam-s...@woa.com.au> wrote:
Dave Henning wrote:

You want to know your total watts

iMac 2.5-1.25 A, 120 W
+120W

LCD Display 1.5 A
_Probably 12V, so +18W, say 20w for ease

Mac Mini 85W
+85W

External Hard Drive .65A 51-80VA
+80W (actually less, but shrug)

Amp 85W
+85W

Lamp 8W, 80 mA
+8W

Say 400w
Is your power requirement.

This would be the minimum you need to buy.

Err, Watts has no time parameter.


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.

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.

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

Sylvia.

 

[Noodnik]

"Sylvia Else" <sylvia@not.here.invalid> wrote in message
news:8o0qmeFimhU1@mid.individual.net...

On 29/12/2010 11:45 PM, terryc wrote:
kreed wrote:
On Dec 28, 6:38 pm, terryc <newsninespam-s...@woa.com.au> wrote:
Dave Henning wrote:

You want to know your total watts

iMac 2.5-1.25 A, 120 W
+120W

LCD Display 1.5 A
_Probably 12V, so +18W, say 20w for ease

Mac Mini 85W
+85W

External Hard Drive .65A 51-80VA
+80W (actually less, but shrug)

Amp 85W
+85W

Lamp 8W, 80 mA
+8W

Say 400w
Is your power requirement.

This would be the minimum you need to buy.

Err, Watts has no time parameter.


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.

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.


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.

 

[Sylvia Else]

On 30/12/2010 12:41 AM, Noodnik wrote:

"Sylvia Else"<sylvia@not.here.invalid> wrote in message
news:8o0qmeFimhU1@mid.individual.net...
On 29/12/2010 11:45 PM, terryc wrote:
kreed wrote:
On Dec 28, 6:38 pm, terryc<newsninespam-s...@woa.com.au> wrote:
Dave Henning wrote:

You want to know your total watts

iMac 2.5-1.25 A, 120 W
+120W

LCD Display 1.5 A
_Probably 12V, so +18W, say 20w for ease

Mac Mini 85W
+85W

External Hard Drive .65A 51-80VA
+80W (actually less, but shrug)

Amp 85W
+85W

Lamp 8W, 80 mA
+8W

Say 400w
Is your power requirement.

This would be the minimum you need to buy.

Err, Watts has no time parameter.


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.

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.


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.

 

[kreed]

On Dec 29, 10:45 pm, terryc <newsninespam-s...@woa.com.au> wrote:

kreed wrote:
On Dec 28, 6:38 pm, terryc <newsninespam-s...@woa.com.au> wrote:
Dave Henning wrote:

You want to know your total watts

iMac 2.5-1.25 A, 120 W
+120W

LCD Display 1.5 A
_Probably 12V, so +18W, say 20w for ease

Mac Mini 85W
+85W

External Hard Drive .65A 51-80VA
+80W (actually less, but shrug)

Amp 85W
+85W

Lamp 8W, 80 mA
+8W

Say 400w
Is your power requirement.

This would be the minimum you need to buy.

Err, Watts has no time parameter.

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.

http://www.powerqualityconsultants.com.au/uploads/Files/Liebert_Powersure_PST_Assistant_-_User_Manual.pdf


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.

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.

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.

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.

 

[kreed]

On Dec 30, 12:27 am, Sylvia Else <syl...@not.here.invalid> wrote:

On 30/12/2010 12:41 AM, Noodnik wrote:



"Sylvia Else"<syl...@not.here.invalid>  wrote in message
news:8o0qmeFimhU1@mid.individual.net...
On 29/12/2010 11:45 PM, terryc wrote:
kreed wrote:
On Dec 28, 6:38 pm, terryc<newsninespam-s...@woa.com.au>  wrote:
Dave Henning wrote:

You want to know your total watts

iMac 2.5-1.25 A, 120 W
+120W

LCD Display 1.5 A
_Probably 12V, so +18W, say 20w for ease

Mac Mini 85W
+85W

External Hard Drive .65A 51-80VA
+80W (actually less, but shrug)

Amp 85W
+85W

Lamp 8W, 80 mA
+8W

Say 400w
Is your power requirement.

This would be the minimum you need to buy.

Err, Watts has no time parameter.

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.

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.

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.

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.

 

[Mr.T]

"Sylvia Else" <sylvia@not.here.invalid> wrote in message
news:8o0uqmFbesU1@mid.individual.net...

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.

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

MrT.

 

[Tom]

On 29/12/2010 11:41 PM, Noodnik wrote:

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.

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