Possible OT: power monitoring

[Frank DiPrete]

Curtis Sandoval wrote:
> All,
>  
>   I have my key systems at home on three UPS battery backups, two 
> TrippLite 900s and a CyberPower 675, all with USB ports for notifying 
> the protected systems of a power failure.  I have two questions related 
> to this:
>  
>   Is there a way, using these or other UPS units, to constantly monitor 
> input line voltage and length of outages?  I recently had three outages 
> within a week and they seem to have been preceded each time by a few 
> hours of low input voltage (112v-114v) but I'd like to verify that 
> and/or possibly preemptively power down noncritical systems to extend 
> the length of battery coverage.  Power quality monitoring would be nice, 
> but my searches seemed to indicate that quality monitoring is much more 
> expensive, and I could find nothing specifically saying that a UPS or 
> quality monitor would report real-time to a computer (specifically SUSE 
> 10.2 or Ubuntu 8.04).

I had a similar problem with cyberpower units.

In my case I have an inline generator and those units saw the power from 
the generator as a power failure. I checked with their tech support and 
sure enough, anything but 60hz perfect sign wave, perfect input voltage 
is a no-go. In your case I suspect the same thing is happening. When the 
grid goes to a low voltage scenario, the ups's are running exclusively 
from battery like a no power situation.

The utter lack of input power conditioning explains why they are so cheap.

I replaced them with APC smart UPS units. The APC units come with 
published input tolerance specs.

Sure enough, the APC smartUPS units took a slightly lower input voltage 
at 58-59 hz and conditioned it, not running off the battery.

I gave one of the cyber power units away and the other is now good for 
propping open a door. (I don't know about the tripplite.)

I got the apc XS 1300 retail at staples for about $265.
It has input quality and load monitoring that is displayed on the unit's 
lcd display in addition to the power conditioning.

>  
>   Also, is there a way to monitor the power draw of a set of devices 
> (say, plugged into the same power strip and monitor the total) or 
> individual device for the purposes of capacity planning for UPS units, 
> akin to a Kill-a-watt device but with some sort of ability to report its 
> data to a desktop?  I have noticed a surprisingly large difference in 
> how long two identical UPS units will last with seemingly similar device 
> loads and would like to be able to determine how large a unit I would 
> need to provide a certain amount of time of backup based on my 
> measurements of average length of (and time between) outages, factoring 
> in recharge times at a given input voltage. 
>  
>   I have been looking at getting some new or larger UPS units, and I've 
> noticed there is a nonlinear relationship between price and capacity, 
> which makes me wonder why a person would not buy two or more smaller 
> units and daisy-chain them to get higher capacity and redundancy.
>  
> Thanks.
> 
> 
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