UPS questions

[PaulJ]

   It's a full sinewave unit, 2200VA, 1600W, operates off 48V of internal sla's.

   Here's a link to the specific model on the manufacturer's site:

   http://www.apcc.com/resource/include/techspec_index.cfm?base_sku=SU2200INET

   I'm considering buying it as a replacement or backup for my 1500W/4500W surge MSW inverter. It isn't ideal, as I currently have a 24V system, but it seems to be a pretty well made unit and it's heaps cheaper than a new full sinewave inverter of similar capacity.

   I have googled and searched this site but still have some questions and would appreciate any help.

   1) What is the efficiency of these units in inverter mode? Is it close to that of an inverter designed for off-grid r.e.?

   2) Are they suitable for continuous use? The person selling it says that it will run indefinitely if I hook it up to an external battery bank which is kept charged by other means, and looking at the specs for the rack-mounted units on the manufacturer's site suggests that battery capacity rather than any issues such as thermal overload limit the run time.

   3) What sort of surges can these units cope with, or is 2200VA the limit?

   4) Will it work as a backup for my MSW inverter if I simply plug the output of the MSW inverter into the UPS input? This alone could make the unit worth buying, but I recall the maufacturers specs saying that a distorted input waveform would cause it to switch to backup mode; maybe it would see MSW as distorted and refuse to operate in standby mode?

   5) How much power do they use in standby mode with the internal batteries fully charged?

   Has anyone here used one of these as inverters in an off-grid situation?

  Thanks in advance for any help!

   Paul.

[nothing to lose]

"  4) Will it work as a backup for my MSW inverter if I simply plug the output of the MSW inverter into the UPS input? This alone could make the unit worth buying, but I recall the maufacturers specs saying that a distorted input waveform would cause it to switch to backup mode; maybe it would see MSW as distorted and refuse to operate in standby mode?"

Not sure what you mean by backup now that I re-read that. Are you meaning for it to run on a second set of batteries as a backup in case the set powering the MSW inverter goes dead? Kinda almost normall use type thing figuring the first inverter is the grid, and if that goes down then the UPS kicks to battery mode as normall.

To begin with I was thinking backup as refferring to a second inverter in case you fried the first one.

 It could possibly go either way depending on the 2 units connected. I have done various things like that and gotton mixed results. Sometimes a UPS works fine off one inverter but then connected to a different inverter it does not work at all.

In trying different things I have had cheap UPS of about 200watts just constantly click and clack switching from inverter power(grid?) to battery backup. But then connected to a different Inverter it would not even turn on at all and then connected to a third (really cheap small) inverter it worked fine.

 I actually ran that cheap 200watt UPS off a cheap 300watt inverter, but the expensive APC UPS (running on Batteries) and the Aims 5k inverter it would not run off of correctly.

I have had similar results in other combinations where one UPS will run on some inverters but not others. I tried alot of cominations. My largest UPS is a APC 1100VA and the smallest ones are those cheapo 200 and 350 watt ones like you buy at wal-mart, I also have some in between like a 600watt APC. My actuall inverters are a cheapo 300watt and a 5k Aims. Some combintions work and others don't!!

I would suggest if it's cheap enough go ahead and buy it and try it, if it doesn't work that way use it for something else or resell it later. Or if you can try it before you buy it and see if it works connected that way. It could just depend on your inverter, it might work on some but not others???

[PaulJ]

   Sorry, I was a bit unclear there now that I re-read the post. I am also thinking of buying the unit as a "backup" i.e a spare inverter, however question 4) did refer, as you guessed, to using it as a UPS off its own internal batteries to take over if the MSW inverter failed for any reason.

   Specifically, I'm thinking of running the (yet to be completed) house off the MSW inverter run through the UPS as backup, and the garage/ workshop directly off the MSW inverter. That way, if I accidentally overload the MSW by using power tools etc in the workshop when there's already a power draw from the house, I will lose power in the workshop but the TV/ fridge in the house will still be working and I won't be shouted at by the rest of the family!

   The overload protection in my MSW inverter seems to be bulletproof, so it would then be a simple matter of resetting it and either turning off some loads in the house, or disconnecting the MSW from the UPS while I (quickly) do whatever I'm doing in the workshop while the house runs off the internal batteries in the UPS.

   Thanks for the reply, it certainly seems like it's worth trying. I can get a refund if it doesn't work with my inverter, so I might as well give it a go.

   Thanks again,

   Paul.

[whatsnext]

Paul, I don't think daisy chaining them together makes much sense. Using your inverter to charge a second set of betteries in the UPS seems kind of complicated when you allready have a big battery back for the MSWI. Also, the UPS will draw a ton of currect if, for some reason, it's batteries are discharged. Plus you will have twice as many battery banks that could fail. I would just use the same bank for both units. So far I have three of the 3000VA sine wave units waiting to go into my system behind a 1600AH 48VDC battery back. I'm hoping that the UPS inverters will stand continous use but only time will tell. I'm just going to build a very redundant and understressed system and hope for the best. Let us all know how the UPS holds up because they seem to be the least expensive TSW inverters available. BTW, don't bother calling APC. They really don't want to hear from RE types.

John..........

[ghurd]

You would be going from DC to AC to DC to AC. At say, 75%? efficient each, thats .75x.75x.75 = 42% efficiency. Thats bad. Real bad.

Maybe I didn't read it right.

G-

[RatOmeter]

I recall the maufacturers specs saying that a distorted input waveform would cause it to switch to backup mode

That is true.  Good UPS's for computers have 2 main tasks (1) keep supplying power when the mains is down and (2) always supply the computer with a clean, stable sinewave.

I am certain that an APC, online sinewave UPS will go to backup mode if it sees something as ugly as a typical modified sine at its input.

[nothing to lose]

Well guys, if it works, to a point I think he has a good idea.

If it works as it should!

First His UPS should have fully charged batts. to start with, so if running from the other inverter it "SHOULD" just be a pass through, I see no real losses there. Maybe some minor loss in charging the internals to correct for self discharge, but I don't think that should be much. Now if something happens and the UPS is running off the batteries, then yes they will need to be recharged to full again and that will incurre losses, but then again that's the reason for redundancy is to keep things working, and they would not be working now if not for the UPS running on the Batteries.

Actually I think myself I would use each inverter as it's own inverter. Since your talking about the same power for each, then use the best one where you need it and the other for the other. Like if you have stuff in the house to make better use of the sinewave then I would use the UPS for the house and the MSW for the shop. Instead of only having 1500 watts of power total, you now have 3000watts total.

If you ran the house on the UPS and the UPS on the MSW inverter, then the house can still only draw the max the UPS can supply if the MSW goes off, and runing everything from the MSW there is a far greater chance of it going off due to over load.

As far as draining your batts. I think it's all still the same amount of power basically. If you still only use a total of 1500watts out of both inverters that's kinda cutting it in half 750watts each, will that increase the life of the inverters compared to running the full 1500 out of just one?

Now I would maybe run the UPS off the MSW inverter for things like computers where you really might want the backup protection incase of a problem like a blown fuse or overload shutdown or maybe the batteries go dead for the MSW for some reason. Something like that could scramble your hardrive just the same as a grid power failure, same thing right! SO for stuff that might need the saftey net I would do that. But really I think otherwise I would not. Just use the best for the house and the other for the shop.

Kinda what I plan to do, run the house off an inverter but then run a UPS also for the computers, then if my house goes dead I have time to safely shut down the computers after I save my work, then go fix the house power. Or if I have enough large UPS's I may just wire each to their own battery set to serve the same purpose, keep power to computers if the house goes dead. But I have 3 system here, and maybe 2 more soon, so that's alot of UPS's also. I would not worry about running computers off of UPS power as a pass through on a UPS and short time on batteries to shut them down in a failure, but I would not want to run them all off the same UPS on battery power all the time.

I geuss it's all a crap shoot how you look at it though.

[PaulJ]

   Yes, the efficiency will be horrible but only when the UPS kicks in - hopefully much less than 1% of the time. Apart from when it's recharging its batteries after use, it would be in standby mode with only a small power draw ( I think).

   Thanks,

   Paul.

[PaulJ]

   Unfortunately my system is 24V and the UPS is 48V, otherwise I would be doing what you suggest. If the UPS inverter turns out to be really good, I might change my system voltage, a lot of work though.

   The 24V battery bank will be doing most of the work; the UPS batts will be on "float" most of the time and should have a pretty good lifespan.

   Maybe I could disable the battery charging function of the UPS and keep them topped up with, say, a small solar setup? It's starting to get complicated though.

   Thanks,

   Paul.

[PaulJ]

   I was afraid of that. Is there any easy way of fooling the UPS into thinking it's seeing a clean input, or of disabling the filtering part of its circuitry?

   I will still give it a try as the guy selling it will give me a refund if (when?)it doesn't work with my inverter.

  Thanks,

   Paul.

[ghurd]

I haven't worked with many types, so this may be way off.

The bigger ones I did work with were a big battery charger, connected to the batteries and an inverter. The inverter ran the 110v stuff from the charger 100% of the time. Just, the inverter was powered mostly from the charger. When the grid supply went down, a dang beeper went off, and the batteries quit charging... that was the only differance.

So, 110v grid to a battery charger DCV supply for the batteries and inverter, to the inverter's 110v output.

75. % would be optomistic for 24/7 operation. Probably more like 20 or 25%.
    
25. % (charger transformer losses, unless its a switcher)x25% (parasites) x25% (last inverter at low/no load, could be closer to 100%) = 1.5%. Yikes!
    
    

Just a poor inverter can drain an " 'bout full" 105ah battery overnight, without a load.

If you are going for off-grid or to save money, I can't see it working.

Extreme Example: Grab a battery charger, totally full battery, and the final inverter. Hook them up together. Plug in the charger. Turn the inverter and charger on. The inverter is putting out exactally 0 watts.

How many is the battery charger taking in?

G-

[PaulJ]

   I don't think this UPS works like that - the guy selling it says it switches to inverter mode in a few milliseconds if there is a power failure, which makes me think the inverter isn't running all the time. Have to check it out though, if it is running the inverter all the time then you're right about the poor efficiency and it wouldn't work for me.

   Thanks,

   Paul.

[notjoe]

I would put an automatic transfer switch between the APC UPS unit and the MSW inverter. The APC would run off the grid/whatever and if that source were to fail then it would fail over to drawing power from the MSW inverter.

I have a UPS somewhat like what you have/are thinking about buying which. While i "Could" run it off my 1500 watt vector inverter it would switch to/from BAtteries/AC every now and then.. i would suggest trying it out first...even if you have to drag the MSW there and run it off your car..

Other/cheaper UPSs i have had no problem running off the same inverter so i think it is really a game of hit and miss.

[whatsnext]

Perhaps you could come up with another way to charge a bigger battery bank for your UPS. That way you would have some real redundancy(two seperate systems) while moving towards a 48V system. I have yet to build my system yet, if you exclude my puny 400 watt MSW and the 150AH batt for it, but it always kind of suprises me when someone wants to baby step their way to a big system. Just because you buy the UPS now does not meen you have to use it right away.

John.........