[TowerTalk] OT: Generators and UPS's

K8RI on TowerTalk K8RI-on-TowerTalk at tm.net
Fri Aug 25 00:52:45 EDT 2006

I have 9500 Watt gas powered generator and use a manual transfer switch.  By 
the time I can make the switch the generator has stabillized.

> I have a generator with an automatic transfer switch. In the event of grid
> failure, I have more than enough capacity to run the house, shack, and
> office (all co-located). I have numerous computers in my office; each has 
> a
> line conditioner (primarily useful for over/under voltage events) and a 
> plugged into the line conditioner.

Do you have real line conditioners or the plug strips they call line 
conditioners which really aren't.  Typically with computers a line 
conditioner is basically a UPS that runs off the battery all the time.  They 
are considerably more expensive than most UPSs and have a very clean wave 

> Yesterday, the grid went down for about an hour. The generator came on 
> after
> about 30 seconds; the UPS's carried the computers during this interval. 
> Some
> of the UPS's began to switch on and off. The generator was running at 
> around
> 40% average load; the voltage fluctuation couldn't have been very much, as
> the line conditioners were not reacting at all. While I didn't monitor the
> frequency, in the past I haven't seen it change much.
> I always set the UPS's for maximum tolerance of noise and voltage. The UPS

I have mine set for minimum although suprisingly the computers can handle a 
really ratty wave form and are not really sensitive to much unless it's a 
really big voltage excursion or spike.

> on my primary computer was one of the ones cycling on and off. It was
> reporting noise as the reason. That UPS, along with all of the others that
> were cycling, died after around 15 minutes.

Sounds like battery replacement time.
It depends on the UPS, but I use APCs. When the original batteries died I 
replaced them with external Lead Acid batteries with a much higher capacity.

> Interestingly, the three UPS's that weren't cycling were Belden 
> 350VA/500VA
> models that I would consider cheaper units. The more expensive APC units 
> and
> some cheaper Conext units all cycled and failed.

As I said above, it sounds like the batteries are ready for replacement. 
Have you run the self test?

> The generator is well grounded and connected to the single point ground 
> with
> 2" copper strap.
> It is pretty certain that the cycling culprit is noise and I doubt I could
> clean the line sufficiently to make the sensitive UPS's behave- especially
> since the line conditioners have noise filters in them already. (There are 
> a
> lot of posts similar to this in the Usenet, but I couldn't find any
> solutions.)

I'd have to see those line conditioners, but I doubt they are really 
"conditioners", but rather just filters using MOVs,

> I need to replace about 7 or 8 UPS's, from 500VA to 1500VA. Has anyone 
> been
> down this road before and found a reliable UPS model and/or brand for use
> with a generator?

I use APCs in the 750 VA range and they now have over 120 hours while on the 
generator. So far I have no complaints. The batteries seem to last about 4 
years although the program complains when the 3 years is up.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com (Use return address from home page)
> Tnx,
> Doug
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