UPS Shutdown in low battery condition

[Anonymous user]

Hi.

I’m interested in:
- UPS Start of Shutdown
- UPS Shutdown Sequence
in a Low Battery Condition

My main reference is:
[NMC-Guide] “User Guide UPS Network Management Card 2”, 990-3402H-001, 08/ 2016

I’m using this abbreviations:
(LBC] Low Battery Condition
[LBD] Low Battery Duration
[MRD] Maximum Required Delay

It’s stated in the [NMC-Guide]:

[A] at p. 26:
“Low Battery Duration
For a UPS on battery, this defines a runtime remaining threshold, below which a low battery condition is triggered on the UPS. For example, if the Low Battery Duration is set to ten minutes and the UPS predicted runtime remaining reaches ten minutes or below, a low battery condition is triggered. If input power is not restored to the UPS, it will turn off when the battery has exhausted.
A low battery condition will trigger a shutdown on all PowerChute Network Shutdown clients associated with the NMC.”

[B1] at p. 29:
“UPS without Outlet Groups
For a UPS with NO outlet groups, the UPS shutdown time is the greater of the Maximum Required Delay or Low Battery Duration values on the NMC Shutdown screen, plus a non-configurable 2 minute delay, plus the shutdown delay for the UPS.”

[B2] at p.29
“Notes
If a shutdown has been triggered by a Low Battery condition, the Low Battery Duration value takes precedence over Maximum Required Delay.”

I’m assuming as true (as described in A) that:
- UPS Shutdown starts in LBC.
- LBC is defined through LBD.

UPS Shutdown Start is determined:
1. In A only by LBD
2. In B1 by max(LBD,MRD)+2 min+UPS shutdown delay
3. In B2 by LBD+2min+UPS shutdown delay

Which sentence is true?

Thank you.

[BillP]

Hi,

Please review page 36 of the attached PowerChute Network Shutdown User's Guide. It explains the shutdown process.

[Anonymous user]

Bill, thank you for the answer.

Although I am not a native English speaker (I'm sorry for my English) in about twenty-five years I have read, studied and understood many ICT manuals.

Before writing this help request, in the last ten days, I have carefully read all the documentation I could find.
As I usually do in these cases, I started with the updated official documentation, including the user guide you attached.

You give me the reference to a page that describes the sequence of shutdown in the event On Battery set in PCNS.

I’m only interested in a low battery shutdown (UPS driven).

The reference does not add anything new to the phrase I mentioned from NMC-Guide:
[B1] at p. 29:
"UPS without Outlet Groups
For a UPS with NO outlet groups, the UPS shutdown time is the greater of the Maximum Required Delay or Low Battery Duration values ​​on the NMC Shutdown screen, plus a non-configurable 2 minute delay, plus the shutdown delay for the UPS. "

I fully understand that LDB must be configured "to allow enough time for the Operating System shutdown to complete"

I asked for an explanation based on the user manual sentences:

A. LDB "Defines runtime remaining threshold below which a low battery condition is triggered on the UPS"
B. If (UPS is On Battery) and (runtime remaining is equal or below LDB) then UPS Turn Off Start.
Before UPS Turn Off it waits the amount of time equal to MAX(LDB, MRD)+2 min+UPS shutdown delay

i.e.

From A: LDB = UPS shutdown time starts

From B: UPS shutdown time = MAX (LDB, MRD) + 2 + UPS Shutdown Delay

-> LDB = MAX (LDB, MRD) + 2 + UPS Shutdown Delay.
The only solution to this equation is UPS Shutdown Delay = -2
🙂

What I'm doing wrong?

Thanks in advance

[BillP · Accepted solution]

Hi,

I'm sorry I feel that the diagram and corresponding text in the PCNS manual explain the NMC shutdown process well. 

On 3/10/2017 1:19 PM, Pierpaolo said:

-> LDB = MAX (LDB, MRD) + 2 + UPS Shutdown Delay.
The only solution to this equation is UPS Shutdown Delay = -2
🙂

The Shutdown delay is based on the number you set

In the example above the shutdown delay is set for 20 seconds. When the UPS reaches 10 minutes of runtime a shutdown signal will be sent to all PCNS clients and they will begin the OS shutdown process. The UPS will continue to provide power for 10 minutes + 2 minutes + 20 seconds. So, once the UPS reaches LBD it will wait 12 minutes and 20 seconds and then cut output. 

If I log into the above UPS and select Turn UPS off and select Signal PowerChute Network Shutdown Clients the UPS will wait 10 minutes + 2 minutes + 20 seconds since MRD is 10 minutes. 

Low Battery Duration	Defines how long the UPS can continue to run on battery power after a low-battery condition occurs.
Shutdown Delay	Defines how long the UPS waits before it shuts down in response to a turn-off command.
Maximum Required Delay	Calculates the delay needed to ensure that each PowerChute client has enough time to shut down safely when the UPS or the PowerChute client initiates a graceful shutdown. Maximum Required Delay is the longest shutdown delay needed by any server listed as a PowerChute Network Shutdown client. This delay is calculated whenever the management interface of the UPS turns on or is reset, or when "Force Negotiation" is selected as Maximum Required Delay. "Force Negotiation" polls each client for information on the time it needs for a graceful shutdown. Two extra minutes to allow for unforeseen circumstances is then added to the calculated time. The negotiation can take up to 10 minutes. If you do not select "Force Negotiation", two minutes is used by default as the shutdown delay for all clients.