[Nut-upsuser] Delayed UPS shutdown

[Harlan Stenn]

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.
>>
>> The ups really should be smart enough to take a delayed shutdown
>> command and be able to do without further commanding from the
>> monitoring nut running machine, something I would think on the minute
>> or minute-thirty delay range, giving the controlling nut machine time
>> to complete its own gracefull shutdown.
>>
>> Is this capability something that can be bought today? I don't see it
>> being advertized in the propaganda when looking for replacement.
> 
> NUT is capable of managing timers and doing delayed UPS shutdowns
> for example by including an "offdelay = 90" declaration in ups.conf
> 
>> Comments/suggestions?
> 
> Perhaps I don't understand your setup.  I assumed that when the 20kW
> standby generator takes over, it substitutes itself for the power
> utility.  Your machining installation sees the wall power return, and
> upsd sees that the UPS status is now [OL].  No need to shutdown the UPS.
> 
> Roger
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?

H