[Talk] Good UPS's

[Carl C.]

talk-request@flux.org writes: 

> From: Nicholas Saraniti  
> 
> At the little GT last night, we briefly discussed GOOD vs APC UPS's... 
> 
> Good == UPS's that will not over draw (amps/watts ?) from a gas
> generator until they are charged  : ) 
> 
> Could someone please post those brand names?

Hi Nick, 

     It was great to meet you and everyone else the other night. 

     The issue really is about how much current a UPS will draw for 
recharging. APCs just pull all they can to feed the batteries (with a max of 
15 amps since most houses are limited to a 15 amp fuse. Some sockets are 20 
amp, but usually have one blade turned sideways to mean "Can do 20 amps"). 
Anything above 20 amps for 120V usually has a rotating socket with large 
blades to handle the higher amps. 

      The usual UPS will just pull current to feed the batteries as fast as 
possible. It's not until you get into the larger systems that usually not 
meant for home use that will regulate the charging of the batteries. I have 
used older Compaq 3KV UPSes and they will regulate how much to feed the 
batteries, but these are larger UPSes, designed to be in the bottom of a 
Rack and are extremely heavy (with 16 gel cell batteries in them). That's 
because they know that your going to use this in a computer room and that 
you may have 30 amps of power in use, therefor, the UPS will only allow 30 
amps to be pulled in max. 

      I know the issue is that if you go on battery power, then as the UPS 
is almost drained, you fire up the generator, you can overload the generator 
because your running the servers and recharging the batteries at the same 
time. The trick is really to provide a larger generator that can handle the 
load (UPS almost dead and keep equipement running). 

      And, APCes are not bad UPSes, you just don't find current limiting 
UPSes until your into the big boy ones. The APCes only know to recharge the 
batteries ASAP, my Compaqs can be programmed to limit how fast you recharge 
the batteries (and therefor, use less current at that moment in time). Now, 
do I recommend these beast Compaqs for everyone, no. They are large, heavy 
and serious overkill for the home user (and you would have to run a 30 Amp 
circuit to feed it). 

      Carl