Date: Sat, 15 Nov 1997 13:09:48 -0600 (CST) From: Kevin Day <toasty@home.dragondata.com> To: dev@wopr.inetu.net (Dev Chanchani) Cc: freebsd-isp@FreeBSD.ORG Subject: Re: Power Message-ID: <199711151909.NAA17156@home.dragondata.com> In-Reply-To: <Pine.BSF.3.95q.971115130536.14527A-100000@wopr.inetu.net> from Dev Chanchani at "Nov 15, 97 01:13:36 pm"
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>
> We had an extended power outage last night. After realizing that our UPS's
> would not keep our network up for the black-out, I ran to sears with a
> credit card and bought a Craftsman generator.
>
> My lesson in power began :)
>
> I was wondering if anyone has been through this and could help me on a
> couple of points:
>
> We have our servers, switches and routers plugged into APS UPS's (600's
> and 650's). The UPS's are plugged into surge protectors. The surge
> protectors are plugged into 15 AMP 12 guage 100 ft extension coards. We
> ran the extension cords (took them out of the wall) and plugged them into
> the generator. The 650 UPS could not take it, it was flipping between
> generator power and UPS power every second. So... my questions are as
> follows:
>
> 1. Can you plug a UPS -> Surge protector -> generator
Yes. If your UPS doesn't like the power the generator produces:
1) Some UPS's have a button on the back of them to set how sensitive they
are. If so, set it to it's least sensitive setting.
If not, you may need to set the UPS to 'bypass' if it has a switch for
that.
2) Get a really really big 'line equalizer' or something of the sort, that
really cleans up the power that a generator produces.
> 2. Are there any specifics I should look for when planning the power setup
> of new servers and racks.
Always buy bigger power protection than you need. APC's Matrix line is
great, because you can keep adding on to it.
> 3. How much output does a genarator need per server (as a rule of thumb)?
It depends greatly. Anywhere from .5A(50 watts) to 5A(500 watts). (if your
generator measures it's output in Volt Amps(VA), 1VA is approximately equal
to 1 watt).
> 4. Was the UPS switching from internal power to external power because the
> generator power was fluctuating, not enough power, etc?
It's because the generator's power in't a pure sine wave, probably, and
it's not too clean. Try to find a big line equalizer, or muck with your
UPS's settings to make it happy. Some UPS's even have a input meant for
generators. When it receives a signal on that line from the generator, it
realizes the power isn't too clean, so it just lets whatever is coming
through pass.
>
> If anyone has experience with this type of stuff, any help and information
> would be greatly appreciated.
>
> Thanks in advance!
>
> PS: To anyone who does not have experience in this, you might want to take
> a look, because its not fun to learn these things in total darkness in a
> ice storm.. ;)
>
>
You probably will want to get bigger extention cords, too. While the total
load from the computers won't pass 15A, the computers plus the UPS's trying
to recharge themselves will. (the UPS's don't know they are on a generator,
they just assume the power came back on, and are frantically grabbing as
much power as they can to recharge themselves, in case the power goes out
again).
Kevin Day
DragonData
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