SC420 does NOT beep

[Anonymous user]

Hi guys,

a complete UPS noob here - I am working with computers for more than 20 years but never needed a UPS up till now. I am setting up a FreeNAS and I've just bought today a used SC420I. I know it's on the small side but it was cheap and the battery seems to be brand new.

I was reading stuff on this site and others, downloaded the PowerChute sw, also the manual and looked for a smart signalling cable. So I am pretty much equipped 😉

When I've got home with this beauty I cleaned it, checked the battery connections and the voltage (13.2V) and it seemed quite a new battery. I also powered up the unit and hooked up a PC I am currently servicing. All good 'online' LED is green. After cutting off the power it is still good and it happily runs on battery for more than half an hour (it didn't go flat I just got bored and switched the power back on).

The problem is when on battery the unit does NOT beep. Is it right? It supposed to beep according what I've read. Could it be that it switched off through PowerChute?

And this leads us to my second question. If I want to test the UPS through my ThinkPad (server is not running yet) and check the settings then which PowerChute would I need? Agent/Server/Console? I mean just to connect and see the settings on the UPS (and not administering other PCs or servers)

Question #3 Which cable should I use between the laptop and the UPS and how to connect them? On the site there is the 940-0024 which is quite straightforward - apart from the fact that on the TP there is no serial port - but what to do with the AP940-1525A? Does the serial bit go to the UPS and the RJ45 to the TP or vice versa? I reckon it is the latter which case I still don't have a serial port on the TP.

I know they seem to be pretty dumb questions for a UPS pro but they are not covered in the user manual 

I would appreciate any help, thanks guys.

[Anonymous user · Accepted solution]

The SC420 supports having its alarm beeper shut off in software and someone may have done exactly that. Pressing the power button should produce a short beep as a response. By default it would beep when running on the battery.

If you don't get that short beep, it's possible that someone physically removed the beeper from inside the UPS.

Regarding monitoring software, you have a few options. Despite its low end status, the SC420 is still a Smart-UPS and as such, it speaks the widely supported UPSlink (or "APC Smart") protocol. You can use any of apcupsd, the long ago discontinued PowerChute Plus, or PowerChute Personal Edition to monitor, test and control the UPS. Or you can simply communicate with the unit by using the UPSlink protocol from within a terminal emulator, which might be the best thing to do if all you want to do is test it out. (The settings to use are a 2400 bit per second communication rate, 8 data bits, no parity, one stop bit and no flow control. Hyperterminal as included with Windows XP and prior works fine. If you are running a newer version of Windows that does not include Hyperterminal, you can use a program such as PuTTY instead.)

APC has documentation covering UPSlink very well on their web site. A quick search ought to turn up a fairly comprehensive PDF manual explaining all the commands.

Since you are just getting started, I would recommend PowerChute Personal Edition or PowerChute Plus (if you can find it -- I believe it's still on the APC FTP site somewhere).

When you get your FreeNAS running, I believe they still package software to monitor your UPS and ensure a safe shutdown of the server. The original FreeNAS (now known as NAS4Free) definitely included such software and it was very easy to configure.

Another program you may want to look up is APCfix. Despite the name, this is not an official APC utility. Its primary purpose is to reset a value known as the "battery constant". If you are sure your unit has a new battery, you will want to do this. That way you can be sure the unit won't shut down before the battery has truly become empty. This program's web site is in Russian, but it's still pretty easy to figure out what to download. (The program itself runs in English.)

The cable you want to use is the 940-0024. Variants with a letter suffix such as A, B, C or D are simply revisions to this cable and will work in the same way. If your laptop hasn't got an RS232 serial port, a USB to serial adapter will generally work just fine. The 940-1525 cable is for a different application and won't work with your SC420. You can buy the cable from APC, make one yourself, buy a cable from a third party or buy a used cable.

I have a much older Smart UPS 420 and it is an excellent UPS. I use it to back up power to my connectivity equipment, something that it will easily do for more than an hour and a half.

Hopefully this post has been helpful. Please feel free to mark it as such if that is the case. And don't hesitate to ask any other questions you might have.