UPS that is UN-interrupt-able;!..

Depends how long it's got to supply power for, and how critical it is that it stays permanently powered. For long enough to shut a computer down gracefully, a relatively small battery in a UPS will do it, with regular testing. For longer periods, a UPS which will last long enough for a standby generator to cut in is what's wanted. Also, how important is clean power? A lot of standby sources generate a very dirty sine wave output.

If it's got a motor in it,then surge rating is important.

In message , at 11:21:23 on Thu, 27 Jan

The batteries have a very limited life in any event - something like a 3 year half-life, approx.

I've been very happy with APC floor-mounted units, and Compaq rack-mounted ones. There's one of the latter with claimed new batteries, on eBay for £268 (inc carriage) at the moment.

PB

In message , at 11:54:31 on Thu, 27 Jan 2011, Paul Bird remarked:

What's their price for the "3000" unit the OP was looking for?

(Curiously, the 1000's seem to be 120v output, and all of them are refurbished, although there's no harm in that).

Have a look at flywheel UPS systems and forget battery life problems. Not sure if they come in rack mounted sizes or if they will suit your needs. Google gives a number of hits on the subject.

John

I feel a project coming on... ;)

Interesting that the wiki article claims flywheel UPS maintenance costs to be half that of a comparable battery-based system; I'm surprised that it's so high.

I've never used an APC that _hasn't_ done this. On a good day you lose some carpet tiles, on a bad day it's a rack with =A320k of acid- etched kit in it.

I've never seen one smaller than about 50KVA, at that point a large chunk of your service cost is just the bloke coming to look at it, all the electronics are very similar a normal one. The obvious killer of small UPS batteries is heat, the last place they normally want to be is in the rack.

Andy Dingley ( snipped-for-privacy@codesmiths.com) wibbled on Thursday 27 January 2011

Weird, because in a job we never had any problems with acid spillage - about 10-15 APC UPSes (2U rackmount, some with the second battery unit, some with "hacked in random lead acid external batteries".

Various devices in the 2-5kVA range.

Sure - we had a very few that lied about the state of their battery - mostly at the 4+ years mark - eg would claim all was well but would last about 2 minutes if mains failed.

That was dealt with by taking them out of service periodically and using a proper battery tester on every battery - then replace. If the batteries seemed serviceable at that age, we tended to use them for less critical kit,

But overall, my personal experience has been quite favourable.

Duncan Wood ( snipped-for-privacy@dmx512.co.uk) wibbled on Thursday 27 January 2011

Possibly why I haven't had these problems - all of mine were in the bottom of racks with ambient air at 18-20C.

I've used MGE UPSs in the past and liked them a lot. I used the double conversion units too (not sure if all their range is like that).

But I think they've just been bought-out by ... APC )-:

Gordon

Might be a good idea to bury the actual whirly-round-and-round bit in a pit - just in case.

I'm with John on this one. You did not mention how long the UPS will be expected to provide power during an outage, and it sounds as if what is really called for is a back-up generator.

I once heard they have a roundabout-sized flywheel at Rutherford Appleton whose energy is dumped onto some unsuspecting and tiny particles from time to time. Is this true ?

Jon

Jonathan Schneider ( snipped-for-privacy@jschneider.tenreversed) wibbled on Thursday 27 January 2011 17:15:

Half my work colleagues go to RAL on a regular basis - I'll ask...

It's slightly more complicated. APC was acquired by Schneider Electric which merged it with MGE under the condition that the sub-10KVA MGE UPS business was sold on and this ended up with Eaton Powerware. Some competition in this area is clearly overdue. I can't believe we are still expected to pay £200 for a web/snmp management module, when we are practically at the stage where toasters come with ethernet ports. Ethernet should be standard on a UPS of any size.

Not sure about RAL, but also in Oxon:

"To our surprise, the intervals of TV advertising spots that are=20 broadcast in the middle of highly popular programmes (e.g. Coronation=20 Street, football finals etc.) are common causes of delays in JET?s=20 evening operations. Presumably adverts cause millions of viewers to=20 switch on their kettles all at the same time!"

I'm surprised they're surprised - I thought it was common knowledge that=20 demand peaks during advert breaks in popular broadcasts.

--=20 Skipweasel - never knowingly understood.

It's odd that. They sit still in a nice clean dry room, never doing any work, and die in three years.

My car battery gets bounced around, frozen, boiled, has to feed 100A spike loads... and lasted 8 years.

Andy