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Is this specific to Lithium battery UPS units?

For home use I bought a lead acid UPS specifically to avoid a fire. For a 5 hour power outage it makes no difference to me if the UPS powers my machine for 5 minutes or 20 minutes; as long as I can save my stuff and shut down it works for me.

> I had an electrician run two 20A Dual Function (AFCI+GFCI) circuits

Don't do this. This is a terrible idea if you intend to run a UPS.

> with hospital grade outlets

Complete overkill and waste of money

> UPS batteries are a big fire risk

No they aren't.

Judging by all these incorrect assumptions about electrical, I'd suggest stopping while you're ahead before you burn your own house down.

> > I had an electrician run two 20A Dual Function (AFCI+GFCI) circuits

> Don't do this. This is a terrible idea if you intend to run a UPS.

Can you please elaborate why someone shouldn't do that? (not who you responded to, I'm just curious about the reasoning behind that statement)

UPS's are notorious for nuisance tripping GFCI's due to the extensive power filtering they usually have inside. It may not happen right away but is dependent on how 'dirty' your power is and on how sensitive your particular brand of GFCI is. All it may take is a neighbour using his AC or power saw and it could generate a spike large enough to knock your system offline (UPS filters spike to ground, leakage current trips GFCI which needs to be manually reset, UPS runs out of battery because no one's home to restore power).

This advice is specific to the US & Canada where GFCI's are calibrated to trip at 5 mA. In the UK, their RCD's trip at 30 mA so it's less likely.

If you read the fine print for your UPS and/or GFCI they will say not to use them together.

What about AFCI's? Well they are basically nuisance devices by design and most electricians hate them. Do not use unless absolutely necessary by code.

The difficulty comes into play because UPS's, servers, etc are essentially industrial equipment while the code is written for such common residential usages as plugging in a lamp (where a dog will chew on the cord, a good way to start a fire hence a perceived need for AFCI protection.)

What if you're stuck because you want to locate your UPS and equipment in an area where GFCI's are required (like a residential basement)? Well I won't tell you what to do in your own home but I'm sure you can devise a creative solution. :)

AFCI's feel like NEC's attempt to create tons of service calls under the guise of "safety". And eventually seems like they will be required for new builds everywhere as areas adopt the newer codes that require them slathered everywhere.

Of course its "for safety" but of course these breakers are famous for false tripping and causing expensive service calls.

anecdote: In my case, small server rack, on circuit a with an AFCI - since "bedroom". No problem.

Until washing machine on circuit b (no AFCI) runs, then trips circuit a's AFCI. Repeatedly, every time(debug on the breaker a returns ArcFault detection reason too). So... either a) don't wash your clothes b) don't have tech or c) quietly violate the code.

Indeed electrician quietly suggested(after a bunch of triage) I swap out the breaker with a normal one. But of course he wasn't allowed to do that... lol

Been here a decade - nary an issue since - so clearly the usual case of nuisance tripping and nothing more.

I suspect the switching power supplies were close to annoying the ACFI, and a beefy motor on an adjacent circuit was enough to push it over the line. Incidentally, swapped UPSes, power supplies(quality Seasonic), etc and nothing improved.

The issues with UPS products tripping GFCI breakers is due to leakage current that is out of spec for the GFCI circuit, this is almost always caused by the load attached to the UPS, not the UPS itself. While most UPS manufacturers do recommend against connecting it to a GFCI outlet, AFCI is required in all new construction for all circuits and GFCI is required for many circuits, including any circuits in basement areas which necessitates a dual function circuit. Since the original thread is about APC, even though I don't use their products, here's what they have to say on the topic: https://www.apc.com/us/en/faqs/FA369034/

FWIW, running my server and network equipment never caused the breaker to trip erroneously while I was still living there. I sold the house when I moved cross-country for unrelated reasons so I can't say what happened afterwards, but my setup was installed according to code and functioned perfectly fine. I used quality UPS and decent quality network and server equipment. Cheap stuff may be farther out of spec and have more issues with leakage current.

> AFCI is required in all new construction for all circuits

This is absolutely false.

Though I'm sure you gave your electrician an earful and he did whatever was needed to keep his customer satisfied and happily took your money. Hope those $50 hospital-grade outlets are working well.

From: https://www.nyeia.com/where-arc-fault-circuit-interrupter-af...

"For new construction, Section 210.12 (A) of the National Electrical Code states that all 120-volt, single-phase, 15- and 20-ampere branch circuits supplying all outlets must be Arc-Fault Circuit-Interrupter protected in the following dwelling unit locations:

Kitchens, Family Rooms, Dining Rooms, Living Rooms, Parlors, Libraries, Dens, Bedrooms, Sunrooms, Recreation Rooms, Closets, Hallways, Laundry Areas, or Similar Rooms or Areas.

Even though it is not listed, this includes finished basements because once the basement is finished, the area becomes one of the rooms listed above.

Adding to the confusion, most people assume that outlets are only plugs or receptacles. However, outlets is defined in Article 100 of the National Electrical Code as “A point on the wiring system at which current is taken to supply utilization equipment”. That means that the requirements for AFCI protection is required in the areas stated above at all 120-volt, single-phase, 15- and 20-amp receptacles, lighting fixtures, switches, smoke alarms, dishwashers, refrigerators, and so on."

So, yes, /technically/ it's not /all/ circuits, however please identify for me a room that's commonly found in a residential property that's not a Kitchen, Family Room, Living Room, Dining Room, Bedroom, Hallway, Laundry Area, Closet or "similar rooms or areas"? Look at the floor plan of most residential properties in the United States and every room noted on that floor plan is on the list. So /technically/ it's not /all/ circuits, so I was /technically/ incorrect, in practice what I said is absolutely true.

Maybe a bit less snark from you and a bit more reading comprehension and you wouldn't come off as such a dick?

You conveniently left out that few jurisdictions are on the 2020 NEC code cycle when this provision was introduced. New codes do not get adopted everywhere immediately. Your town or city needs to adopt it and that can take many years. So, no, not all new construction.

> Judging by all these incorrect assumptions about electrical, I'd suggest stopping while you're ahead before you burn your own house down.

For anyone reading this, this person has no idea what they're talking about. Besides the fact that I once considered becoming an electrician and completed my apprenticeship prior to entering the tech industry, it is a published standard how things should be installed in residential properties in the US, called the National Electric Code or NEC.

The NEC 2020 states that GFCI is required (in additional to a general AFCI requirement) for any 125V or 250V receptacles in kitchens, bathrooms, laundry areas, finished or unfinished basements, garages and anywhere within six feet of a sink. Since my server rack was in a closet in a finished basement, it is /REQUIRED/ by code to have a dual-function breaker.

Also, I once again refer you regarding fire risk to simply search "UPS fire datacenter". UPS fires are the primary cause of datacenter fires. But sure, I don't know what I'm talking about, I've only been responsible for multiple datacenters spanning the globe for one of the world's largest hosting providers as part of my career after giving being an electrician a go and deciding against it as a career in my youth.

If anyone is ever in doubt about how to install something that's electrical: 1. Hire a certified electrician and 2. Read the applicable standard, which is the most recent published version of the NEC. Don't listen to people who make rude smart-ass comments on the Internet.

> UPS fires are the primary cause of datacenter fires

Do you have a source for this claim? I can find no documented evidence of it being true.

The Uptime Institute found[0] data center fires of any cause to be exceedingly rare. Data Center Incident Reporting network reached similar findings[1].

The only example I could find of anyone claiming data center fires have a principal cause is this article[2], and while I'm not saying it's wrong, I've never heard of these folks before and have no idea how credible they are:

"Electrical failures are the most common cause of data center fires. These failures can stem from overloaded circuits, malfunctioning equipment, or defective wiring, each capable of generating sufficient heat to ignite a fire when in proximity to combustible materials."

(Note: they break out battery fires separately, so they are not supporting your claim that batteries are the most common cause of data center fires.)

But, in any case, with details about data center fires being so rare, either because they are rare or because people don't want to talk about it, stating a primary cause accurately seems to me to be very difficult.

Lastly, since you've run multiple data centers, surely you understand the scale of the battery strings involved. Total energy storage is way higher, ampacity is higher, and to the extent lead acid batteries are involved, much, much, more hydrogen off gassing is possible. I just don't see how you can extrapolate that down to fire risk for a 12V, 12AH battery found in a typical home UPS.

0 - https://journal.uptimeinstitute.com/datacenter-fire-frequenc...

1 - https://www.datacenterdynamics.com/en/opinions/how-frequent-...

2 - https://dgtlinfra.com/data-center-fires/#:~:text=Electrical%....

The fact remains that GFCI/AFCI aren't really doing anything to address the UPS battery fire risk you're describing, while increasing the chance of problems that knock the power out.

Also the NEC has gotten ever more outlandish with those requirements. Like last time I looked there was no exception for sump pumps, yet you'd be foolish to actually use a GFCI there. Actually a quick search says it's now even explicitly required. rolls eyes. I mean sorry, I'd love to but I'm just too busy restraightening all the prongs on my plugs due to these wonderful "tamper resistant" receptacles.

After using hundreds, hundreds of very cheap to huge expensive APC UPS' I can say I have never experienced a fire. They have all used lead acid batteries, some as heavy as 50lbs. I have even had to cut UPS' open to remove swollen batteries.

Can't you buy a UPS with a LiFePO battery, or find an old lead acid one and do a battery swap?

UPSes with dead lead acid batteries are a dime a dozen. People don't realize or don't both servicing the batteries and toss them out all the time.

I love hooking up large lead acid batteries to old UPSes, there's no reason to be limited by the original battery capacity.

However...I discovered why some APC UPSes are sealed and the battery cannot be accessed. I was converting one such UPS which had no monitor interface. Having already opened it up to splice in an external battery, I noticed an empty header for a serial port. Cool. Plugged that into my PC and flash/bang/smoke. Fortunately my PC had a good path to ground and was not damaged. But the UPS had some pretty large burn marks at various points in the PCB and was certainly dead.

It took me a bit to figure out what I did wrong. The reason it went bang is directly related to why there's no user access to the battery, and why there's no external monitoring port. They went cheap on the electronics and did not include an isolation transformer. Any points within the UPS which are "ground", including the battery negative terminal, are actually referenced to the full bridge rectifier, which provides a direct path to live. Ahh...I'm just very glad I didn't touch any of the battery terminals while I had the thing plugged in.

What’s the failure mode you’re guarding against by having the UPSs on separate circuits and breakers?

Is the idea to protect against a breaker failing, a wiring issue, or something similar?

Nonsense. UPS's don't pose any sort of serious fire risk. UPSs starting on fire are exceedingly rare. Sure, it's probably happened. People get hit by lightning too.

I'd guess they are certainly safer than a laptop, but it depends on a manufacturer... (I've seen lots of "balooned" laptops, including many Macs)

Not to be snarky, but UPS fires are one of the leading causes of datacenter fires: https://duckduckgo.com/?hps=1&q=UPS+Fire+datacenter&ia=web

Right and data center fires are extremely rare. Think of how many UPSs are in the wild. The failure by fire rate is probably something like 0.000001%.