[asterisk-biz] backup power requirements for emergency calling

[Andrew Kohlsmith]

On Friday 14 April 2006 17:54, alex at pilosoft.com wrote:
> This is why asterisk guys should stick to doing asterisk, and leave
> facility management to people who know that.

Seeing as I am a field applications engineer for an industrial power 
electronics company with over ten years' of experience in this field, I find 
your comment not only amusing, but also downright incorrect.

Asterisk is my hobby, but one I am very good at.

> No, it is not. You want your genset to start within 30 seconds after power
> goes out. If it doesn't start, you might have 20-30 minutes to correct the
> problem before UPS battery goes kaput.

It's all about coordination.  If you wait 20 minutes before starting the 
genset, you typically make sure you have 30-40 minutes of battery.  You also 
test the generator and transfer switch once a month to make sure everything 
still works as expected.

> Also, note that 20-30 minutes runtime is about average for a facility UPS.
> So, you *definitely* do not want to drain the battery to the end before
> starting genset.

20 minutes may have been a bit of a stretch, but I typically see 50% usage on 
the UPS before the genset is started.  You do *not* want your 600kW genset 
cycling for 2-3 minutes whenever a squirrel or raccoon falls across the lines 
or tries to nest in the transformer and trips the breaker, especially since 
the breakers will automatically try to clear the fault 3 or so times before 
staying tripped off and notifying a human.

-A.