General > General Technical Chat
UPS options
PaulAm:
I'm in the midst of a multiple day power outage and my UPS decidedly does not like my backup generator. I thought that was because this is an old generator with a mechanical speed govenor which starts at 62Hz dropping to 60Hz once you get to about 30% load. Having not much else to do, I tried running the UPS when the generator was under load and it still didn't like it. It kept switching on and off battery.
Power outages are not uncommon and, since I'm in a rural area, I'm often at the bottom of the priority list. One and two day outages happen a couple times a year.
Because this is a multiple day outage, I bypassed the UPS so the server rack could come up, but I'd rather just let the UPS carry over the systems until the generator is up and running.
So what are my options here? A double conversion UPS? Some kind of power conditioner? Replacing the generator is not an option (this is a 16KW generator, 66A, 240V at 60Hz)
gnif:
If your UPS is capable of 100% duty a stopgap might be to convert it to be a fully online UPS if you have a power supply of the right voltage and high enough current to power it in parallel with the batteries.
David Hess:
I have used 4 different online UPSes over the years with my 3 kilowatt inverter generator and they all worked fine. I have heard that various offline UPSes are much more picky.
bdunham7:
You probably should have a careful look at the output of the generator. There may be a reason the UPS doesn't like it. My line-interactive and off-line UPS boxes all work find with my sub-$1K inverter generator. Mid-to-low grade regular backup generators can have some awfully brutal outputs, especially if you have a poor power factor load with harmonics. If you really want your stuff to have clean power you may need a full double-conversion, aka online UPS.
nctnico:
You also need to oversize the generator otherwise it can't deal with non-resistive loads. Rule of thumb I got told is a factor of 2. But this may not be applicable to 'inverter generators'.
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