"Turn Off Delay" Query

[simonbrads_apc]

Hi all,

I'm finding some of the terminology used in the user manual for my UPS inconsistent and somewhat confusing, in particular, as related to the main and switched outlet groups. I have a Smart-UPS 1000VA LCD (SMT1000I).

The user manual mentions:

• UPS outlets
• Main group outlets
• Switched outlets
• Group 1 outlets

The term "UPS outlets" is only used in the "Customize the Main and Switched Outlet Groups" table. Does it mean the same as "main group outlets"? And am I right in thinking that "group 1 outlets" are the switched outlets? (Presumably, bigger units have "group 2 outlets" as well.)

The user manual lists the "Turn Off Delay" default settings as:

• 0 sec (UPS Outlets)
• 90 sec (Switched Outlet Groups)

However, there's only one "Turn Off Delay" setting (I think?), so how can the different groups have different delays?

As a test, I told my UPS to "turn off - use delay". Everything switched off after 90 seconds, so it looks like all my outputs are behaving as switched outlet groups. Maybe the point about "UPS Outlets" is an error in the doc, and doesn't relate to my UPS at all?

I've just realized that the main outlet group can't have a delay less than the switched groups, as this would violate the "master switch" property of the main group: the switched outlet group can only be on while the main group is on, right? (Unless the main group is told to switch off only after the switched groups are switched off, so the main group's delay is, in effect, added to the switched groups' delay?)

Sorry for asking such newbie questions, but I've read through the user manual several times, and I still don't quite get it. 🙂

Thanks for any advice you can offer!

Cheers,
Simon

[voidstar_apc · Accepted solution]

>
Sorry for asking such newbie questions, but I've read through the user manual several times, and I still don't quite get it. 🙂
>

It's confusing -- I think you understand it better than most.

>
The term "UPS outlets" is only used in the "Customize the Main and Switched Outlet Groups" table. Does it mean the same as "main group outlets"? And am I right in thinking that "group 1 outlets" are the switched outlets? (Presumably, bigger units have "group 2 outlets" as well.)
>

--"UPS Outlets" refers to all UPS outlets, both main and switched.-- UPS Outlets refers to the main outlet group. Group 1 is the switched outlets, and yes, bigger units have group 2 as well.

>
The user manual lists the "Turn Off Delay" default settings as:

- 0 sec (UPS Outlets)
- 90 sec (Switched Outlet Groups)

However, there's only one "Turn Off Delay" setting (I think?), so how can the different groups have different delays?
>

The 0s delay might refer to older UPSes that don't have outlet groups, or the main outlet group.

>
...Unless the main group is told to switch off only after the switched groups are switched off, so the main group's delay is, in effect, added to the switched groups' delay?
>

Correct. Today, the off delay on the main outlet group starts only after the switched outlets have finished turning off.

[simonbrads_apc]

Thanks very much! With a little extra testing, and with the hints you provided, I've now got my head around the on/off delays (and also the load shedding options).

I do think the user manual could do with a once-over by a competent technical author, though. 🙂 (e.g., "UPS outlets" is used in one place, without having been introduced; "main outlet group" and "main group outlets" both refer to the same thing; etc.) (I should admit that I'm quite pedantic, but I get to edit technical documents at work, and these are the sorts of things I pick up on. 🙂 )

[BillP]

I think your comments about the user manual are accurate and perceptive.  To say that the manual could do with a once-over is a very kind. You are not being pedantic in this case, as the document is inconsistent, incomplete, and unnecessarily terse.  

I ran into another usage document that can help: "APC APPLICATION NOTE #165, Switched Outlet Groups on SMT and SMX Smart-UPS" By Neil Whiting, found at: www.apcmedia.com/salestools/NWHG-8SJN9A/NWHG-8SJN9A_R1_EN.pdf (also attached).  While this note gives some good examples of how the switched outlet groups can be used, it does not provide any help with how to use the LCD interface to configure the examples on a given UPS.  This is unfortunate, since for many users, the LCD interface will be their first experience, e.g., before they get the PowerChute software working.

[BillP]

On 1/20/2012 11:35 AM, voidstar said:

--"UPS Outlets" refers to all UPS outlets, both main and switched.-- UPS Outlets refers to the main outlet group.

The above is confusing, as it defines "UPS Outlets" twice. When does "UPS Outlets" refer to all UPS outlets and when does it refer to the main outlet group?  

[voidstar_apc]

It's been a while since I wrote that so I'm not sure exactly what I meant. Looking over the UPSes I have access to, there's an SMT750 with a single Main Outlet Group called "UPS Outlets". In that case, main outlet group is also all of the UPS outlets.

I think it's difficult for the tech writers to describe how to use the switched outlets because their functionality isn't an exact match for the problems they're designed to solve. For example, if you want to stagger turn-on of the outlets to minimize inrush current on startup, you can set the turn on delays. But that same turn-on delay also applies when in-rush isn't an issue such as commanding a single outlet to turn on.