Back-UPS XS 1000

[Anonymous user]

What condition or situation would result in the F06 error message, "Relay welding"?  Does this point to something in the computer-room environment that needs checking out?

[Anonymous user]

There are several relays in the Back-UPS that perform various functions (one to turn power on and off to battery backed outlets, another to connect the inverter to the load and a third that enables the AVR function). This fault code means that one of them is mechanically stuck, most likely by contacts that have literally welded themselves together over time.

A small electrical arc takes place when electrical contacts make or break under load. Over time this degrades the contact surfaces inside a switch or relay and may ultimately result in them being stuck together at all times. Unless your Back-UPS XS 1000 is heavily loaded (more than 60% of its capacity rating) nothing in your computer room has directly caused this, and even in that case, it was just time and wear.

These units aren't considered as repairable by end users. Subjecting the unit to minor mechanical trauma (tapping it on the floor or rapping it with a fist, either to be done only after removing the batteries) might be enough "encouragement" to get the relay unstuck. That probably won't be a lasting fix, though. Once the contact surfaces have bonded together, even if you get them unstuck temporarily, they'll just stick again at some point and may continue to degrade to the point where the relay becomes hot and breaks down.

[Anonymous user]

William, thanks very much for such a thorough explanation.  The unit is about five years old and now, of course, has been replaced.  The unit supported only one PC and LCD monitor, so I think it was well within its capacity; but I wanted to check about the possibility of external problems, just in case.  Thanks again.  /Mike

[Anonymous user · Accepted solution]

You are certainly welcome. If my post answered all of your questions, please feel free to click the "answer" button to indicate such.

Although the official stance is that these units are considered non-repairable by the end user, and I'm not sure if APC actually repairs any units that come back under their limited warranty, some of the more minor faults can be repaired if you fully understand the hazards, have some experience in high power electronics repair and are willing to accept all responsibility for whatever results you may get. The hazards of working inside one of these cannot be understated, they really can be VERY DANGEROUS to work on. You'll certainly void any warranty the unit has and nobody can take any responsibility for what happens, good or bad, as a result of attempting a repair.

Compatible replacement relays are available at any decent electronic components supplier (such as Digi-Key or Mouser).

These units are pretty well protected against faults on their output, and should simply shut down in an orderly fashion if shorted or overloaded.

I'm not affiliated with APC or Schneider Electric in any way. I'm just an end-user of their products who speaks only for himself, and someone who has repaired quite a few of them over time...which is not to say that they're unreliable, I just tend to buy a lot of them as parts/not-working/fix/etc. and refurbish them.