Largest UPS on a 15A circuit?
Skeleton Man
I just bought a Smart UPS 1400VA but it doesn't give quite enough runtime..
I was looking at 2000VA+ but they all have 20Amp plugs and I have no 20A
circuit to attach an outlet to. How big can I go and still keep a standard
plug ?
I am NOT running a big load.. the idea is to run a SMALL load on a BIG UPS
and get over 1hr runtime.. 2AMP load on my 1400VA gives about 45minutes..
Would I be better off buying big SLA batteries and rigging up a connector ?
(this unit is standalone)
Generator is a last resort.. it's noisy and can't go in the house.. not to
mention who wants to be fighting with a pull cord when it's dark and -25C
outside.
The UPS fits under my desk and silent apart from a small cooling fan when
it's on batteries..
Chris
John McGaw
The power rating of the UPS is not the best predictor of runtime -- whether
the load is low or high. The real deciding issue is the size of the
batteries. If you had a UPS that used deep-cycle marine batteries rather
than little gel cells you would have an incredibly long runtime. Normally,
a heavy UPS is a good UPS.
Probably the easiest thing you can do is to buy a UPS that takes external
battery packs. IIRC APC makes some although they are far from cheap. Or a
really hardcore hardware hacker could buy a recreational vehicle
inverter/charger, hook up the proper number of deep-cycle batteries,
install the whole rig in a stout cabinet in the garage, and run
interruptible circuits to the needed areas. Some people with conversion
buses have similar setups and are able to run an air conditioner overnight
without running their generator.
Just my $0.02 of course...
--
John McGaw
[Knoxville, TN, USA]
http://johnmcgaw.com
philo
Yes just hook up a large gel-cell externally..
I have been running several UPS's here with some pretty large batteries
and have had it working fine for years
VanguardLH
15A * 120V = 1800KVA at the wall
Presumably you are connecting more than the system case (and whatever is
connected to it) to the UPS, like your monitor at a minimum and maybe
optionally your powered speakers, printer (inkjet only, not laserjets),
scanner, etc. You might want to reconsider and hookup only the system
case and monitor to prolong battery drain.
A UPS should provide a scale of expected runtimes under various loads.
If you want a longer runtime, you need a bigger reserve, and that means
bigger batteries (i.e., higher ampere-hours).
Which would have a longer runtime under the same under-max load?
- 1000KVA UPS with one 12V 12AH battery
- 1000KVA UPS with two 12V 72AH batteries
Both have the same KVA rating (at max load) but the second has 12 times
the capacity.
I had an old Best Power 2200KVA UPS (defunct and now owned by Powerware)
whose 2 batteries with the removable bracket weighed in at 70 pounds and
the case with the huge isolation transformer weighed another 40 pounds.
I took it apart when I moved it. The major mass in the case the
transformer because this was an isolation UPS which produced
true-sinusoidal A/C output power, not stepped power (which isn't needed
for the PSU in the computer case but little other computer equipment
employs switched power supplies). It was overkill but it was free to
me. I kept it for 12 years and simply replaced the batteries twice
(bought them locally, not the overpriced units from the product vendor,
but did have to fashion my own bus bars) until its logic board went bad
(and it definitely wasn't under warranty and no longer supported).
Since all the connected computer gear put under a 1/5th load on the UPS,
I had something like 2 or maybe 3 hours of runtime will all gear
functional.
You might only connect the system case and monitor since these are the
only critical components that you need (i.e., just wait until later to
do your printing later, to play your games with speaker output, to scan
in documents, and so on).
The KVA rating simply states what is the maximum rated load on the UPS.
A larger KVA rating doesn't guarantee longer runtime. A higher KVA
rating does mean a larger battery is required to provide that peak load
but doesn't dictate how long the peak load can be maintained. Typically
the larger KVA rating results in just big enough increase in battery
amp-hours to give the same full/half load runtimes.
Also runtime is nonlinear to the load. At max rated load, you might
only get 5 minutes of runtime. At half load, you might get 15 minutes
of runtime (half the load, three time the runtime). At 1/7th of the
rate load, you might get an hour of runtime (1/7th load, 12 times the
runtime). See http://www.powerware.com/UPS/5115_specs.asp as an example
of battery runtimes based on load (for the 1400KVA model). Have you
actually ever ran the UPS until its shutdown after near-full drain? The
runtime guestimate in the display could be way off.
Some UPS brands and models allow you to extend the runtime by adding
external battery modules (EBMs). You can't just slap more and larger
amp-hour batteries in parallel to the existing ones because the charger
inside the UPS won't handle that load, especially when the batteries are
nearly or fully drained. You can see how EBMs will increase runtime at
http://www.powerware.com/UPS/9120_Specs.asp. With their 2000KVA model
and 5 EBMs, you get 8.4 hours of runtime at half load, but you are
probably around 1/10th load so you might get around 4 days of runtime.
Of course, these aren't cheap UPS units at this point. Most users don't
want to spend more on a UPS than they spent on their computer but that
also means they don't get high runtimes. At the prices for *good*
200KVA UPS models with decent runtimes, you might want to start
rethinking the generator setup since that would not only let you have
power for your computer (until you ran out of fuel) but also your TV,
room lights, cordless phones, to make meals, keep the fridge running
(which could be costly if you have it loaded and the outage is for more
than a day). However, you probably want to have only certain circuits
on the generator since they also get pricey as you up in wattage. Of
course, you need to keep a fuel supply on hand and keep the tank filled
with fresh fuel (under 3 months old).
Typically a UPS is employed for data protection, not hardware usability.
The point is to provide enough time to gracefully shutdown your
applications to protect the integrity of your data. They also come in
handy to keep your cordless phone usable during an outage, to keep the
router and cable modem up (meaningful only if your ISP is also still
up), and perhaps a coiled fluorescent lamp so you can see your way
around the room, but you might want to use multiple UPSes for all of
those instead of paying logarithmic prices for linearly increased
runtime.
Just for giggles, and since you like APC products, you might want to try
using APC's UPS calculator:
http://www.apc.com/tools/ups_selector/
Use settings for however you might later expand your computer when
adding components, like adding hard drives, etc. Use the future reserve
to figure out what you might need for your next greatest, more powerful,
more expensive new computer that you might get later. Once I entered in
a full decked out version of my next computer (which only would be when
I get another UPS), gave it 20% reserve, and a 2-hour runtime (full
load), I was at the $800 starting retail price range.
kony
So long as the system load + UPS battery charging current is
lower than the rating for the AC circuit, you can use a
larger UPS. Given the runtime you get already it is not
likely a wall-plugged UPS will have high enough battery
charge current that it would matter.
You could instead buy big SLA batteries if you like, though
with some UPS being smarter than others you can run into a
couple issues. Is is the UPS reports a problem with the
batteries because they take too long to charge. Another is
the reported runtime remaining as it may expect a certain
amount of capacity vs the load drain rate. Another is it's
estimation of when the battery needs replaced, a big battery
worn out might trick it into thinking it's a smaller battery
still functioning well.
I have to wonder why you are aiming for what seems an
arbitrary amount of runtime. If the power is out for longer
than 45 minutes, what are the odds it won't be out for more
than your target of over 1 hour? What gain is there really
in having an extra 15+ minutes if the system is probably
going down from the outtage anyway?
Skeleton Man
>arbitrary amount of runtime. If the power is out for longer
>than 45 minutes, what are the odds it won't be out for more
>than your target of over 1 hour? What gain is there really
>in having an extra 15+ minutes if the system is probably
>going down from the outtage anyway?
I work from home and get paid by the hour, so an extra full hour to work in
a blackout is neccessary. 1 hour seemed do-able at a reasonable price - what
I'd really like it to be able to run off batteries for about 5 hours. Power
outages for 5 - 45mins are the most common, but occasionally we will see a 3
or 4 hour blackout and I'd like to keep working right through it.
What I am powering is this:
PC/LCD monitor
Cordless phone
Router
I'm on fibre optic for phone and internet, which has its own battery backup,
so I just need to keep my own stuff running.
Chris
kony
5 hours on batteries seems unrealistic, including that this
is a long time to go without power to anything else. I'd
aim for a fuel powered generation plus a mere few minutes
UPS runtime seems more realistic unless you have no place to
put the generator. What about using a power efficient
laptop with a high capacity battery in it when power goes
out? That would leave your UPS far more runtime to power
the phone and router, maybe even power the laptop for a bit
of that time.
philo
I have a total of three *large* UPS's in my workshop...
two of them have 24 hours of reserve
here is a picture of one of them
kony
Nice setup, but not everyone has room for a rack and that
array of batteries. Part of my reply was considering that
if power is out for several hours, at some point continuing
to work on a computer becomes less important than cooking
food, refrigeration, coffee in the morning, etc. These
things become possible given a large enough generator, but
not realistic on an UPS.
philo
Who needs to cook food...
oops I see you mentioned coffee!!!!
Even though I have a lot of batteries here...I's not sure is my UPS'
could handle a coffee maker.
I know that I am such a geek here and have so many UPS backup systems...
that my GF and I are sometimes working away (or goofing off) on out
computers and don't even realize there is a power failure.
Anyway because I repair industrial equipment for a living
I have access to plenty of free, surplus equipment >G<
rjk
"philo" <ph...@privacy.net> wrote in message
news:b4adnWFqBK3ftS3U...@ntd.net...
>
> Anyway because I repair industrial equipment for a living
> I have access to plenty of free, surplus equipment >G<
Care to share the wealth? ROFL.
-rjk
philo
Sure...
I'll gladly send you a used...battery free...
you pay the freight for shipping...
Of course. it's not cheap to ship a 70# battery...
plus with hazardous material fee...it would cost a small fortune...
Maybe I could interest you in some modems>>>
I've got plenty of them <G>
CBFalconer
> rjk wrote:
>> "philo" <ph...@privacy.net> wrote:
>
... snip ...
>>
>>> I have access to plenty of free, surplus equipment >G<
>>
>> Care to share the wealth? ROFL.
>
>
> Of course. it's not cheap to ship a 70# battery... plus with
> hazardous material fee...it would cost a small fortune...
>
> Maybe I could interest you in some modems>>>
>
> I've got plenty of them <G>
Have you got a V92 external modem, preferably by US Robotics?
--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
Try the download section.
rjk
I feel your pain. I probably have more. I really need to just throw them
away.
By "equipment" I assumed you didn't mean "consumables" or "supplies"
:-/
-rjk
philo
I am in the industrial battery & charger business...
but at one time I also did a lot of UPS repairs too