[Nut-upsuser] Delayed UPS shutdown

Roger Price roger at rogerprice.org
Thu Jan 2 11:43:42 GMT 2020

On Thu, 2 Jan 2020, Harlan Stenn wrote:

> On 1/2/2020 3:12 AM, Roger Price wrote:
>> On Wed, 1 Jan 2020, Gene Heskett wrote:
>>> But I should preface this with the fact that I have a 20kw nat gas
>>> fired standby with a sub 10 second startup time in the back yard.

> My understanding is:
> If there is a power outage, there comes a point where the UPS says "I
> have N minutes of power left", and when N is small enough we want upsd
> to shut down the boxes.  As soon as that decision is made, boxes will be
> told to power down, and boxes MUST power down.
> If line power comes back at this point, but before the UPS runs out of
> power, the UPS MUST power cycle, as the boxes will only power up when
> they see the power turn off and then turn on again.
> Anything else, and while the UPS may not *need* to power down, if it
> doesn't turn off/on then the boxes won't know it's OK to power up again.
> Or am I misunderstanding something?

The key factor here is that Gene has a 20 kW standby, and I assume, an automatic 
transfer switch.  In his case, the wall power supply is restored within 10 
seconds. He never gets to the point where the UPS says "I have N minutes of 
power left".

Gene, do your rotating machines stop during the time it takes the standby to be 
ready to take over?


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