On Nov 17, 2010, at 09:31 AM, Daniel Clark <[email protected]> wrote:
On Wed, Nov 17, 2010 at 12:25 PM, Chris Hoogendyk
<[email protected]> wrote:
> I have no idea how that home brew UPS you linked would have performed in a
> similar situation.
Thanks - at least one useful thing I've gotten from this thread is
that whatever I end up doing, it would seem to make sense to have
smaller COTS "front end" UPS units, connected to whatever backend (be
it COTS or DIY), and have separate "front end" units for servers and
HVAC.
Well, yes and no. :-) The problem with having separate units is that you don't have parity between the uptime of the servers and the HVAC. So, if you're HVAC batteries run out before your server batteries then your servers begin to cook. It would be better to have a single system so that everything goes down at once. You will have an outage, but at least your servers won't be physically affected.
I found this calculation on the web. Once you know the variables you should be able to figure out what you need for the missing variable. So, if you know you need 8 hours of runtime you can get the battery specs from your manufacturer of choice and run the calculations.
Number of batteries = N =20
Voltage of each battery = V = 12 V
Ampere-hour of each battery (AH) = X
Number of Operational hours = T = 2 hrs
Volt-Ampere = (N * V * X)/ T
15000 = (20*12*X)/2
15000 = 120X
X= 125 AH
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