Date: Sat, 15 Nov 1997 12:34:04 -0800 (PST) From: Mostyn/Annabella <mrl@teleport.com> To: dev@wopr.inetu.net (Dev Chanchani) Cc: freebsd-isp@FreeBSD.ORG Subject: Re: Power Message-ID: <199711152034.MAA24040@user2.teleport.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
I thought about doing similar - Here are some replies from UPS makers:
1. Tripplite
MHS: Source date is: 14-Oct-97 11:04:09 -0500 CDT
None of our units were made to run on line with generators. The
reason is because most generators do not put out a pure sine
wave or do not have the hertz controlled at 60. What we have
come across is that when there is a power outage and the
generator "kicks in" our units will still stay in battery. The reason is
because our units need to see good power going into them in
order to come off of battery power.
2. Liebert
I would not recommend using the POwerSure Interactive on the Coleman
5000, as the PowerSure Interactive will switch to battery each and
every time the frequency goes out of range, as well as when the
voltage does. This would in affect have the PowerSure Interactive
switching to batteries every few minutes. The optimum solution would
be to have an online UPS as with an online UPS, the UPS will not
switch to battery for frequency deviations. Specifically with the
Coleman 5000, I would recommend not to use anything larger than the
UPStation GXT 1500 which is an online UPS. As a general rule, Liebert
recommends sizing a generator application at a 3:1 ratio. (Size the kW
of the generator 3x the size of the UPS).
The main reason that Liebert recommends an online UPS is that when the
frequency deviates, an online UPS will "free-run" utilizing its own
oscillator to generate the frequency. A line interactive or off line
UPS must transfer to battery.
If you have any further questions, feel free to contact me.
3. APCC
Although I am not familiar with the Coleman generator specifically, here are
some guidelines that we recommend when selecting a UPS / generator combo:
- Use a Smart-UPS, which can be desensitized to allow the slightly less than
perfect generator power to pass through. If this is not done, the UPS will
detect a less than perfect sine waveshape and will stay on battery.
- Use a computer grade, pure sine wave output generator.
- Make sure that the generator is oversized by at least 4 times the load
which you will be placing on it. In your case, the 5000 watt generator should
have a load of no more than 1250 watts placed on it.
Mostyn Lewis
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