Surge suppressors

David Mathog mathog at
Fri Nov 1 10:13:54 PST 2002

> > surge suppressor.  It ran ok for an hour  with "openssl speed"
> > running in a loop on all nodes. These suppressors may have
> > too small a breaker if we add second CPUs to each node but
> I think that they might.  Those CPUs use a lot of power, and the
> switching supplies, if not PFC, appear to have a PF of around 0.8 (so
> you draw a peak current about 1.25 higher than what you might expect
> based on average power.  We couldn't get 10 nodes on a 20 A circuit
> here -- had to settle for 8.  Which means that with 5 you'll be right on
> the same margin, where YMMV depending on how sensitive the protector is
> to peak vs average current and how much other stuff you have in the
> nodes that draws current.

So - what are you using for surge suppression on your 8 nodes on
one 20A circuit?  (Or do you have a UPS?)

Since it's actually 20A all the way to the wall receptacle I suppose
if/when we actually get the second CPU we could plug a second
Tripplite Ultra 6 into each wall socket and put 2 nodes on one, 3 on
the other. That should keep the load below 12A on each surge suppressor
and below 20A overall on the circuit.  Pretty ugly though having that
many power cords and surge suppressor bricks.

I just don't get the manufacturers' choices for surge suppressor
lines.   For some odd reason the joule ratings seem to go down
on most lines of surge strips as the current limits go up.   Both
the APC and Tripplite rack mount models, for instance, don't
have particularly large joule ratings.   Max joules also tends to be
lower, in general, in units with metal cases than in units with
plastic cases - see, for instance, the Intermatic product line.

On paper, at least Surgex, Brickwall, etc.seem to have all the
oomph one would ever require.  But their prices are very high.

Are my selection criteria unreasonable?  All I want in a strip is:

6-8 sockets
big MOVs (high joule rating - longer expected lifetime)
metal case with some holes in it (for zeroU mounting,
  I'd accept a plastic case if there was some way to
  mount it in the rack that didn't involve glue or duct tape)
disconnect sockets on MOV failure
15/20A breaker (fuse would be ok).


David Mathog
mathog at
Manager, Sequence Analysis Facility, Biology Division, Caltech

More information about the Beowulf mailing list