[Beowulf] Opteron cooling specifications?

Bari Ari bari at onelabs.com
Mon May 1 10:49:09 PDT 2006

Mark Hahn wrote:
> sure, there's no downside to 220 afaikt.  one thing I don't fully 
> understand is where the 80% figure comes from.  just a fudge-factor,
> and what if you wind up always using that extra capacity?
> presumably an L6-30 circuit is actually safe to run at 30...

Safe to run sure, but it probably won't run reliably.

Typical circuit breakers in load centers are electromechanical devices 
that conform to the Underwriters Laboratories UL Standard UL 489 
calibration test. This test, a subset of the entire UL 489 Standard, is 
intended to determine proper electrical circuit breaker function in 
response to overcurrent. Breakers are tested at 135% of rated load and 
should trip within an hour. 20-Amp and 15-Amp breakers are tested at 
200% of rated load and should trip within 2 minutes.

What breakers are not tested for is the trip time when operated at under 
its current rating. It is not uncommon especially as the breakers age or 
have been tripped repeatedly, to trip at less than 100% of its rating. 
I've replaced breakers many times that would trip when under 80-95% of 
its rated load after several minutes.


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