Mailing List Archive: "installing UPSes isn't hard"

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.
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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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