Clearly you've never owned a UPS the size of a large DC Plant. One of the ongoing problems with UPS boxes is they have batteries in them, too, and they have to be managed and maintained. one of the BIGGEST wins in going with House DC as a source is that there is just one battery plant to be managed, and it is always rated for at least 8 hours continuous full load. sizing a UPS for that much is very, very expensive. If you wanna run AC, use inverters from House DC. That's just a UPS with the crap made redunant by a huge DC plant left off. If you insist on buying AC-powered things, then you will have inverters somewhere, either inside the UPS box or outside connected right from the DC plant. EIther way, there are many more parts involved to break. the MTBF WILL be lower. there is no way around that. The Telco folks have 100 years of hard-won experience and some of it is worth borrowing to prevent learning it the hard way. But if you insist on relearning them, be my guest. Just don't offer bad advice to other impressionable young minds. cheers, -Mike O'Dell VP, Chief Scientist UUNET Technologies, Inc.
Mike O'Dell writes:
Clearly you've never owned a UPS the size of a large DC Plant.
I've never *owned* one myself, no -- my needs at home are pretty small. :) On the other hand, I've been involved in projects in which entire floors of users and large machine rooms had to have substantial run time off of their red outlet equipment (that is, the UPS equipment), and the UPSes involved were indeed gargantuan. The maintainance was indeed nasty, but luckily the electricians took care of that :)
one of the BIGGEST wins in going with House DC as a source is that there is just one battery plant to be managed, and it is always rated for at least 8 hours continuous full load.
Perhaps you are reading too much into what I said. I merely said that having enough AC capacity for user demand was a good idea, not that DC was inherently stupid.
If you wanna run AC, use inverters from House DC. That's just a UPS with the crap made redunant by a huge DC plant left off.
Well, fine -- why not have house inverters, then, for the AC users. Anyway, I don't want to argue about this too much. Its not worthwhile, and the arguments on both sides aren't particularly wrong. My point was merely that a colocation facility CAN provide decent amounts of AC and ought to, given that most off the shelf equipment runs on it and that you can put together enough UPS capacity to keep both sides happy.
The Telco folks have 100 years of hard-won experience and some of it is worth borrowing to prevent learning it the hard way.
I'm curious -- are there any Bell System Tech Journal articles or similar on this from way back? I imagine similar discussion must have occurred a long time ago... Perry
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Perry E. Metzger