[rescue] Real amp draw of E3000

Mike Meredith very at zonky.org
Thu Sep 21 12:11:12 CDT 2006

On Thu, 21 Sep 2006 09:54:34 -0400, William Enestvedt wrote:
>    I *love* real world data, thank you!

Not sure about real world data but some real world experience ... not so
far back I watched half a 'data centre' loose power twice in 5 hours
because of loading issues (and a *very* big burn out fuse).

>    Have you got any idea about the amps, though? I think my twin PDUs
> are rated for 20 amp (on 20 amp circuits, I know that much!), and I
> want to put in a V40z (10 amp max.) where I already have a 420R (6.3),
> a 4-CPU E3500 (9.5), a 280R (9.2), a 12-drive A1000 (2.6), and a 15"
> CRT.

Amp? Isn't that what you use to make sounds bigger ?

Systems have a specified load that's far bigger than they usually draw
... after all most of our systems (even the 10-CPU E4000s) aren't loaded
with as much power-sucking stuff as they could be (an E4000 probably
draws more power with 2 CPUs and loads of I/O boards with funky SBUS
cards, and a few disk trays).

So the fact that you're running systems totalling 30amps on a 20amp PDU
isn't too surprising. You may or may not be able to add the V40z to the
mix, however ...

Systems draw more power when first switched on I believe (and certainly
a qualified electrician explained what happened that way) so in the
unusual circumstances of powering on a whole PDU-worth of equipment at
once, you can well overload the PDU which works with the systems in
'steady state' mode.

After our burnt out fuse was replaced, we reset the PDU (somewhat bigger
than 20amps) and the above was exactly what happened to us ... the
starting load overloaded the PDU and it reset back to off. Ensuring that
half of the systems were off before resetting was somewhat tedious.

I think I was in for 20 hours that day.

It's safest to assume systems will pull their maximum specified load,
and work around that. More expensive too though.

>    *sigh* Maybe I should have stayed in engineering school instead of
> getting an English degree...

Well, maybe. It's worth noting that even the PHB in charge of
implementing our new data centre (in a previous life was regularly
handling much more electrickery than even a large data centre pulls) was
most insistent that the electrical requirements were handled by
currently qualified electricians.

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