I found out the hard way, do not plug your laser printer into the battery side of your surge protector. It drains the battery. I figure most people know this, but I did not.

jimmie,

I figure that if you buy a laser or phaser thingy and the lights don't dim when you use it, then obviously it's not powerful enough to kill someone when you need it to, so take it back.

Dan,

HA!! Well the laser printer is A-OK, but the 600 APC surge protector failed me. Wonderful timing, but when I decided to install my new medical dragon 2 halfway through the install the computer went black and lost power and the partial install had to be wiped clean and new reinstall done a bit later. ugghghghgh
Not to mention, I have my laser printer plugged into the surge protector side now.

Good tip.

Yes, laser printers pull 500-600W. One of the most power hungry items in an office. Highly recommended to put them on separate outlet/circuit from any important equipment.

Even if not in the battery outlet, it will still continuously trip the UPS.

Thanks Sandeep,

I am learning from the Maestro!!!! Now the really strange thing, my watch battery died the same day--think of the odds of that happening. Will get it plugged in separately.

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=bpl12578

I am not a maestro, but I agree with one. Most printers, and specifically HP printers, are recommended to be plugged directly into the wall.

I actually didn't know there was a 'battery' end on my surge protector. I did try plugging everything into my UPS once, and it became quickly clear that we cannot print scripts after the power is out - at least without the generator running. Now we have an emergency generator, lights, etc.

Chris,

I don't feel like reading this thread again, but the only way to have a battery is to have an UPS. Most UPSs have one side that protects with a battery/surge protector/AVR while the other side just has surge protectors.

All UPS will tell you not to plug printer, copier and scanners into the battery side or anywhere in the UPS for that matter. When you think about it when the power goes out, you really don't need to print, copy or scan.

We were going to try and print scripts, but we found out all there is time for is to get all the systems safely shut down before we run out of battery juice, usually about an hour or less. Now I use that time to fire up the generator if I want to keep seeing patients, and take the UPS cord and plug it into the generator's extension cord.

Even if a UPS battery is large enough, manufacturer still quietly recommends not powering a laser printer. A UPS in battery backup mode is some of the 'dirtiest' power inside a building. Since electronics are so robust, then that 'dirty' UPS power is also ideal power. But 'dirty' UPS power can damage small electric motors and power strip protectors.

For example, this 120 V sine wave UPS outputs 200 volt square waves with a spike of up to 270 volts. Again, ideal power to electronics. And a problem for protectors and motors.

A utility also demonstrates how 'clean' AC mains sine waves are replaced with 'dirty' power when the UPS switches to battery:
http://www.duke-energy.com/indiana-business/products/power-quality/tech-tip-03.asp

Connecting to 'surge protector' outlets is electrically same as powering the laser from any other receptacle on the same branch circuit. No magic device is between a wall receptacle and those surge protected outlets. Open it up. It remains a direct (hardwired) connection. No magic exists inside that UPS.

westom,

Your link describes the event more accurately than I did earlier. There was a loud continuous bleep when the computer screen went black and computer turned off all at once. I was finally able to get the bleep to stop by pushing the reset button and plugging the computer to the surge protector side only. So I took the battery out of the APC device and took it to the local battery shop today and it was shot.
So maybe a better description of the event was a computer lock up.

Also, if I read your post above correctly, theoretically one could plug a computer on the battery back up side and a laser printer on the surge protector side of the APC 600 UPS device and it should function appropriately, however the company discourages this.

Jimmie, I have used the APC 600 for years with the printer plugged into the surge protector side only and have not had a problem. What I have noticed is that the back up batteries can fail without warning, as happened to you last week. I have upgraded to a Cyberpower brand UPS for my server. It has buttons that I can push to tell me the voltage, health of the battery, etc. These are available on Amazon and other places.

The other question for the technical experts is how many surges can an APC 600 or other UPS handle before it goes bad? I wonder if this is why Jimmie's unit failed as we have power fluctuations and we have had several lightening storms this summer.

In looking for an alternative for APC for an SMB client with our enterprise group, we decided to try out CyberPower, and the results were positive enough that became their data-center standard when they did a hardware refresh. Better instrumentation on the front, and from a cost perspective we can get them with 2-day shipping on Amazon Prime and no sales tax, making their net cost lower than our cost via distribution.


In theory, their durability should follow the same pattern as elastic versus plastic deformation; if you don't cook the power regulating circuit, they should last indefinitely. In practice, The batteries almost always go first. Better units have replaceable batteries, which means you don't have to buy the whole assembly again (or unrack it).

One thing to watch for is heat build-up or cell failure - I've had to pull apart racks/enclosures more than once where a cell failed and literally twisted metal.

Although, again, you read the manual for certain companies. Some printer companies state they want the printer plugged directly into a wall circuit, and the fine print will void your warranty.

Cyberpowers are clearly the best. Agreed.

Imagine two light bulbs connected to a common AC receptacle. When one goes bad, does the other stop working? Of course not. That is how the UPS works. One 'bulb' represents a protector. The other 'bulb' is power provided to a computer or printer. Protector circuits can completely fail. And it still connects a computer or printer directly to AC mains - no power interruption.

Every useful answer includes numbers. A potentially harmful surge is hundreds of thousands of joules. How many joules does the UPS claim to absorb? Hundreds? Near zero protection inside a UPS means advertising can hype it as 100% surge protection. Advertising fables manipulate consumers who ignore numbers. Spec numbers identify a UPS that is only near zero protection.

UPS connects a printer or computer directly to AC mains when not in battery backup mode. It switches to batteries and creates 'dirty' power during rare power outages. That function continues even if protector circuits have failed. A consumer would never know. Since superior protection, already inside each appliance, remains functional. And that UPS still outputs power.

Expect a UPS battery to seriously degrade or completely fail every three years.

Please help me understand what the difference is between plugging a laser printer into the surge side of the UPS (with no battery backup) as opposed to directly into the wall, if they are both receiving direct AC current. As I would understand it, there is no battery power involved and the laser printer is dead if the power goes out. In Jimmie's case, he had plugged the laser printer into the battery backup directly.

Bert-are you saying there is no way to protect a laser printer from a power surge? It would seem to me that banning use of the surge protector would be a good way for the printer manufacturers to make money selling more printers when customers' printers are destroyed from a power surge.

Laser printers have a brief need for a very high amount of electrical power while heating the printing element. That has improved a lot, but was the basis for my comment that the lights would dim when using a laser printer in the past. Maybe the lights and plugs were on the same circuit, which is not up to code.

That suction needs a surge from the grid, so there could be a conflict between the printer and a surge protector, even though a small printer and healthy surge protector should be fine. Plugging into the battery supported side of a UPS would trip the alarm.

I haven't heard of printers going out from electrical surges like computers, but don't have problems with surges around here.

Hi everyone,

Even this may not be that helpful, this link

http://en.wikipedia.org/wiki/Surge_protector

says don't believe all the numbers.... Scroll down to "Joules rating."

Gene

Hi everyone,

This may get a bit technical, so if you're not into this area, just skip this post. I've always had an interest in electricity. Back in my younger days I did quite a bit of wiring, and I still keep my hand in electrical and HVAC diagnosis and repair! My firsthand experience with electrical surges occurred last summer. As a result of windstorms, our office was without power for about 24 hours. Power was then restored for about 30 minutes. I was able to come to our office during this time, and noted that several circuit breakers were tripped. I tried to reset them, but they would instantly trip again. Shortly after this, however, the power went off again, and stayed off for about 24 more hours.

When the power came back on, I tried to reset the circuit breakers, and they reset normally. I tried to turn computers on, several would not power on. When I unplugged them from this surge protector strip, and plugged them directly into the wall, they powered on normally. We did not lose a single computer.

However, of 7 APC surge protector strips, five were damaged. On one or two, the "loss of protection" light was illuminated. The rest appeared normal. However, when I physically opened the cases, electronic components were obviously badly damaged, and there was evidence of smoke and melted plastic inside. All of our battery backups were fried as well, these were APC as well.

I believe that, during the brief time power was restored, it was at a significant overvoltage. These surge protectors burned up internally, protecting (successfully) the computers.

I find the mechanism of this surge protector interesting. It appears that, regardless of brand or cost, the basic protection in all of them is pretty much the same. There is a small solid-state device, connected from both the hot and the neutral line, running to the ground. At normal voltages, this will not conduct electricity. But when the voltage rises above threshold, it will conduct power from that line to the ground, basically providing an intentional short circuit, try to keep the overvoltage from reaching the computer. In our case, I believe that the current to ground exceeded 20 amps, and tripped the circuit breaker.

I have several conclusions from this episode. First, someone asked how many surges can be absorbed. Unfortunately, there appears to be absolutely no way of knowing this. My surge protectors were obviously fried. However, several of them did not indicate a problem by the indicator lights. I am planning to replace ours every time there's indication of a significant overvoltage, and I've arbitrarily pick three years as replacement interval.

Secondly, all of our critical or expensive electronic equipment is plugged into a surge protector, including printers. I don't really understand the printer maker's recommendation not to use a surge strip, I suspect their concern is that a low quality surge strip may have undersized wiring, and cause a voltage drop to the printer, or that numerous items may be plugged into it, again in a poorly designed surge protector this could cause problems. But one printer plugged into a surge strip, plugged into a wall outlet, can't possibly cause a problem, and may save the equipment during an overvoltage. It did save ours!

Third, I believe that battery backup (UPS) are very fragile when it comes to significant overvoltages. All of ours fried. Since last summer's episode, I have been plugging the UPS into a surge strip, and then into the wall outlet. Important: the surge protector goes between the battery backup and the wall outlet, not between the battery backup and the computer!

Finally, as also mentioned above, test your UPs. I just pull the UPS plug out of the wall, see if the computer will stay on, and give it 15 or 20 min. to make sure battery life is sufficient. Last year Sandeep indicated concern about this method, he was concerned about loss of grounding when you pull the plug. But when you pull the plug, you are disconnected from power, so you don't need grounding. Sandeep mentioned that there would be a possibility of a stray current coming in through an ethernet cable or so forth. For our applications, I don't think that is a concern.

Hope this helps someone!

Gene

The lights dimming is bad news - but all the more reason to not run computer on that circuit, or run them with a UPS/power conditioner.The lights dimming typically indicate a low voltage in the circuit or high amperage in another segment.


The purpose of the power conditioning is to add or reduce voltage downstream so that the resultant output power is in range. They work until they don't - and then they don't ever again.

Thanks for all the great responses!

It is extremely humbling (in a good way) and curiosity pleasing to introduce a topic and learn much more than I ever intended from a simple issue that I never even thought about until a few days ago.

But any explanation on why my watch battery and APC 600 battery died on the same day?

Most likely drained by an alien spaceship hovering overhead....

Gene

Lots of good stuff in this thread.


Those are the main concerns. Lots of outlets share the same circuit. They want to make sure you don't plug your printer and your computer on the same circuit in case there is a drop in voltage while the printer powers on. That would shutoff the computer. Also, most circuits are 15A x 120V = 1800W watts max. Back in the day when computers and screens weren't energy efficient, you could reach that maximum and trip the breaker. (Many outlets share the same circuit.)

Your strategy is great. Surge protectors everywhere. The voltage tolerances on those things are so high so anyone saying that they might trip due to some device pulling too much or too little is just not true. They have very high tolerances and are mainly designed to prevent damage rather than conditioning. In a major over voltage, those are the best defense against losing expensive devices.


One of the biggest confusions in electrical circuits is the difference between an Earth and a Ground. The ground reference of all electronics is not necessarily at the same potential as the Earth depending on the design. There's an Earth ground and a Chassis Ground. The Earth ground and Chassis ground can be the same thing. But in high end electronics, the power supply can have its own ground level (potential) which is different from the Earth (hence the reason it is referred to as a floating ground.) Without getting too technical, this design of a separate ground allows a device to better resist interference. So, basically, if you remove that Earth ground, you or one of your devices may become the path of least resistance since the Earth ground is no longer part of the circuit. (e.g. when a UPS runs on battery power while it is unplugged.)

O and the thing about dirty power from UPS's. That's not really an issue today with "pure" sinewave UPS's available. Cyberpower's Pure Sinewave models have been even found to have power that is almost identical to the output of the wall. The reality is that most modern PSUs are designed to handle the approximated step waves anyways. Look it up on youtube. They deliver.

Tripplite also makes some good stuff. I use cyberpower in the budget range (Pure Sine Wave models from amazon, free shipping) and vary brands in the enterprise range (we have 250V NEMA 6-30 outlets in our office for running server racks.) I learn towards Tripplite because that's usually where I get my server racks.

A destructive surges was both incoming to and outgoing from all protectors and computers simultaneously. If a surge is incoming to the protector strip, then that same surge was also outgoing into each computer. First that surge flows everywhere simultaneously in that path. Much later something in that path fails.

Generally, protection already inside computers is superior to protection inside power strips. So what failed? Weakest protection. Making that protector undersized got you to recommend it. A surge too tiny to harm the computer easily damaged an undersized protector.

Effective protection means a protector does not fail. In your case, the word fire should cause you concern. A NC fire marshal describes their fire house fire.
How much money for each protector? Compare that to a completely different device also called a protector. One 'whole house' protector (rated at least 50,000 amps) means everything is protected. For about $1 per protected appliance. Even a direct lightning strike does not damage a properly sized protectors. The spec number (50,000 amps) says so. Significant experience confirms it.

This time you were lucky. Protection inside all appliances was sufficient to avert damage. Unfortunately, you credited a grossly undersized protector.

A UPS is made a cheap as possible. So even it was less robust and suffered damage.

What happens inside a protector? Grossly undersized MOVs must disconnect as fast as possible while leaving that surge connected to appliances. Sometimes a thermal fuse does not trip fast enough. Resulting burned MOVs violate even MOV manufacturer specifications. MOVs must never fail catastrophically. Unfortunately MOVs were not disconnected fast enough. So some protectors were on the verge of fire. Does that get your attention?

Again, a surge catastrophically destroyed protectors while, at the same time, could not overwhelm protection already inside computers - and numerous other appliances inside the building. How many dimmer switches, GFCIs, CFL bulbs, refrigerators, and smoke detectors were damaged? Many are typically less robust than computers. What protected them?

Hi Sandeep,

Then I'm confused.

First, in terms of AC power, there are typically three wires that come to a device. One, which is black, is referred to as the hot. The second, which is white, is commonly called the neutral. However, this is technically called the grounDED conductor. At the electrical service (circuit breaker box) where it comes in the building, this one is tied into the groundING system. Everywhere downstream from the circuit breaker panel, the white is separate.

The third is the wire are of interest, called the groundING conductor. This is bare copper or green in color. Again, at the circuit breaker panel, this is connected to the white. However, at this panel, it is also connected to the earth. It is connected to two eight-foot rods driven into the earth, to the cold water plumbing system (unless plumbing is all plastic), and if available connected to a Ufer (one of the reinforcing rods in concrete of the building foundation or concrete pad).

The purpose for the groundING system is just as you described. If you electrical items were to become energized, and you touch that item and something connected to the ground, such as a kitchen sink, a bathroom tub, a concrete floor in a basement, or so forth, then electricity would flow through you and into the ground, completing the circuit. Not a good thing to have happen!

So most electrical devices are grounded, meaning that all the non-energized metal of the device is connected to the grounding system, through the third prong of the plug. So if there is a failure in the device, which brings voltage to the housing or a case of the device, it will immediately flow through the grounding system, and presumably trip the circuit breaker, protecting the user from shock.

So, based on the above, earth and ground should be the same.

The exception would be after a transformer. When the electricity goes through a transformer, it no longer has the connection to the ground (earth). So if you were dealing with the output of a transformer, you could touch that, and touch the water pipe, and not be shocked, because no connection exists between those two. If your use of the term ground, separate from Earth, refers to electricity downstream from a transformer, then the two could be different. However, in this situation, the electricity coming out of the transformer could not shock you!

Similarly, a device running strictly on a battery backup (UPS) would have no connection to the earth, so grounding would not be necessary.

Except in this specific situation of dealing with output voltage from a transformer, ground (groundING) and Earth are the same. This is my understanding of it. If I'm wrong, please tell me where.

Thanks.

Gene.

Hi Westom,

Do you have any data to confirm this? Any specific brands?

Thanks.

Gene

Protectors that work come from manufacturers with names that any guy would know for integrity. Including GE, Square D, Intermatic, Syscom, Siemens, Polyphaser, Leviton, Ditek, or ABB. A Cutler-Hammer solution was selling in Lowes and Home Depot for less than $50.

Protection is never defined by a protector. A protector only acts like a hardwire when that incoming utility cable cannot connect directly to earth. Protector life expectancy 'over many surges' is defined by it important parameter - 50,000 amps.

Why 50,000 amps? Lightning is typically 20,000 amps. A protector must earth a direct lightning strike AND remain functional.

Protection during 'each surge' is defined by what absorbs hundreds of thousands of joules. Earth ground. (Earth ground is electrically different from a safety ground on wall receptacles). How to make a protector even better? Upgrade its single point earth ground (all four words have electrical significance). And make that connection even shorter (lower impedance).

Effective protectors from those manufacturers always have a dedicated wire for the earth ground connection. That must be low impedance (ie 'less than 10 feet').

BTW, that is only 'secondary' protection. Each protection layer is defined by its earth ground. A picture demonstrates what must be inspected in the 'primary' protection layer - especially on every transformer:
http://www.tvtower.com/fpl.html

A protector is only as effective as its earth ground. Of course, this is mostly irrelevant to what the OP asked about. A UPS in battery backup mode may be harmful to motorized appliances (ie laser printer).

So the take home message is--

You should have a surge protector for your laser printer, plugged into a different circuit than your computer. The computer should have a separate surge protector/battery back up or UPS to allow one to shut down safely in the event of power failure. And this battery in the UPS has an average life of 3 years.

Please correct me if I am wrong. Also, all kinds of brands and options are available as described above.

Outlets in each room will usually be on the same circuit, so this might not work. But it might be worth the trouble for extra insurance to make sure your main computer for AC or your server does not have a laser printer on that circuit.

Gene,

Wi n?t trei a h?liday in Sweden this y?r ?
See the l?veli lakes
The w?nd?rful teleph?ne system
And m?ni interesting furry animals
Including the majestik m??se
A M??se once bit my sister...
No realli! She was Karving her initials ?n the m??se with the sharpened end
of an interspace t??thbrush given her by Svenge - her brother-in-law -an Oslo
dentist and star of many Norwegian m?vies: "The H?t Hands of an Oslo
Dentist", "Fillings of Passion", "The Huge M?lars of Horst Nordfink"...
Mynd you, m??se bites Kan be pretty nasti...

I think the interspace toothbrush interfered with something down here..

I am having a flashback to a prior thread.
I dream I am in a sailboat, on the Chesapeake, with a sailor at the helm, but he has had a few too many beers. But it never happened.

I'll have what he is having....

Gene

Did this involve Iron City Light???

Gene

jimmie,

I would not get too hung up on the issue of separate circuits. If possible, fine, but should not be a problem to have them on the same circuit.

The two best names seem to be CyberPower and APC, Tripp Lite is good too.

Anything expensive or critical should be plugged into a surge protector or battery backup (UPS)

The larger the UPS, the higher the battery capacity, so the longer the run time when the power is off.

Simple enough?

Gene

Got it.

My simple fix. I replaced the shot battery on my old 600 APC for about 20 bucks, bought a new 600 APC. Plugged my computer on the battery side on the new one which I plugged into a receptor on west wall of office. Plugged my laser printer into the surge protector side of the old 600 APC and plugged this into the south wall receptacle, and am investigating the circuitry, just so I know.

Once again thanks for all the extremely useful information.

I agree with Gene.

First, I will back off some, but when you search on HP and surge protectors, it will show you the ones that are for that printer. I am not sure what people are talking about when they say same curcuit. For me it is like your dryer which only runs on on one probably two circuit breakers.

While the UPS can "condition" to some degree, it isn't close to a system with Automated Voltage Regulator or AVR which does many more.

I think, just my perspective, as Gene alludes to, this whole top has been over done. While I have Cyberpower AVR 900 and 1500 UPSs for computers and switches and routers, I just let my copier and printers sit there and frankly, would sleep pretty well with none of it. Except for the holy grail, the server. Just plug them in.

I can neither confirm nor deny the presence of Iron City or any other adult beverage on a sailboat. Having stood many watches at the helm, I have *never* had too many while at the helm, so I have nooooo idea who JBS has in mind.

Well, there is "African Queen" ....

Fortunately or unfortunately, it was strictly under the influence of ice cold, Vitamin D laden, grass fed Holstein produced,whole milk.

Hi jimmie,

Probably no need to check circuitry.

Most electric circuits are 20 amp circuits. Sandeep mentioned 15 amp, in the "modern era" lighting only circuits may be 15 amps, but most "receptacle" circuits are 20 amp.

There are two potential concerns. One is overloading the circuit. This usually can be explained in 2 words: Space heater. Or toaster. Or hair dryer. The devices that use the most electricity are those that generate heat. Classic scenario: Circuit breaker trips in December. Anything different? No....well....maybe the space heater under my desk that I didn't tell you about....In this instance, the loads must be distributed, so a single circuit does not have more than a 20 amp load on it.

Note that a breaker will trip at a continuous load of over 20 amps. A momentary load, like a motor starting. may involve very high current flow, but should not trip the breaker.

The second involves voltage drop. This is involved in the "lights dimming" phenomenon mentioned earlier. A heavy load (air conditioner or heat pump starting) will momentarily pull A LOT of current. This effect is more pronounced if it is on the same circuit as the device you are concerned about. This is especially pronounced if there is a very long distance from the circuit breaker panel to the load, or if the circuit is heavily loaded with other devices.

If you notice a problem when printers/air conditioners/etc start, then you might look at which receptacle is on which circuit, and even have to run a new circuit or two. The huge majority of the time, unless the breaker trips, no problem.

A UPS is very helpful in this situation. Typically the UPS will monitor input voltage. If in an acceptable range (often 105-135 volts) it will let the device run on AC power. If the input power goes outside of this range, then AC is disconnected, and the device runs on battery, just as if there were a blackout.

Gene

Gene,

I appreciate the followup regarding the circuitry.

But I am still a bit puzzled why my computer lost power and the screens went black, when I still had electricity at the office. I could understand the battery failure beep indicator on the 600 APC device going off, with just battery failure alone but why the loss of power to the computer? Would a computer lockup manifest this way?

This UPS typically switches to battery backup mode when voltage drops so low that incandescent bulbs dim significantly. That is what it should do. Temporary power. However these things are made so cheaply as to be fooled even by electrical noise. In your case, its battery was defective. If AC line noise caused the APC to switch to batteries, then batteries could not provide sufficient power to the computer.

A resulting lockout was cleared by pressing its reset button. Does not matter if sufficient AC power was incoming. That UPS had completely disconnected from AC. And then locked because its battery was nearly dead.

Plug a laser printer directly into the same duplex receptacle that powered the UPS and computer. Electrically same as when plugged into the UPS 'surge protected' outlets. Power demands, as demonstrated by Gene's numbers, are well below what would cause problems on properly wired circuits.

Hi jimmie,

Here's my guess. a UPS will have 2 ratings. One is for the available power when on battery backup. This may be, say, 300 watts (watt=volt X amp, so 300 watts = 300/120 or about 2.5 amps.)

The second is total output when on AC power, which would be the total of what is plugged into the battery backup, and the surge protector outlets. Lets say this rating is 12 amps. If the computer and monitor take 2 amps, and the laser printer 10 amps, then the 12 amps could be met or exceeded. Then an internal circuit breaker (in the UPS) could have tripped.

So why at that particular time? Either one of the devices took more current, or the "trip curve" of the circuit breaker would allow a certain current for a certain period of time, and the time was exceeded.

In either case, an internal circuit breaker would open, and any devices plugged into either side of the UPS would go dead.

The circuit breaker sometimes resets automatically, sometimes there is a button for you to press to reset.

Or, the UPS is starting to go bad.

So the computer is an "innocent bystander."

Make sense?

Gene

westom and Gene,

I have never taken the time to understand this type of gadgetry, but with a disrupted install of Dragon my attention was grabbed, so I thought the topic might be pertinent to fellow AC users.

My initial intent was to warn others of avoiding the mistake I made.

I spent over an hour last night trying to google my last question above before I posed it here so your answers are once again much appreciated and thanks for the rational well written responses, from a guy who is trying to rapidly catch up on things not necessarily learned along the way.

That's why engineers exist. A 15 amp breaker may take 2 hours before it trips on a 20 amp load. We dumb numbers down. For example, we provide a ballpark number to associate a 14 gauge wire with a 15 amp breaker; a 12 gauge wire with a 20 amp breaker.

Turn five 100 watt incandescent bulbs on at the same time on a 15 amp circuit. How much do they demand on power on? Maybe 30 amps. Why does that not trip a 15 amp breaker? Electrical concepts say why. We dumb it down. Five 100 watt bulbs consume 4.2 amps continuously. We just forget to mention the initial 30 amp consumption is normal for a 15 amp breaker and 14 gauge wire. Discussing such details confuse layman.

We know why a UPS is not recommended for a laser printer (obviously not to be confused with an inkjet printer). Motorized appliances do not like the 'dirty' power provided by a typical UPS in battery backup mode.

Even noise could have tripped that UPS into battery backup mode. Then the UPS discovered its battery was defective in about 2 seconds. So it locked out all power - crashing your computer. No circuit breaker need be involved since other electronic circuits can cause the resulting power off and Alarm.

What would happen if five 100 watt bulbs were powered from surge protected outlets? A resulting maybe 28 amp demand would not trip any circuit breaker.

We know a UPS powering a motorized appliance is not recommended because UPS power can be so 'dirty'. Not undersized (insufficient wattage). 'Dirty' power is ideal for electronics and potentially harmful to motorize appliances and power strip protectors. Reality is always this much more complex.

Here's the issue. Not all are grounded to the same potential. Like I mentioned earlier, in some devices, the chassis ground is not the same as the Earth ground. In some devices which are highly susceptible to interference, the chassis ground is kept at a different potential. That's where the term floating ground comes from. It's kept above the potential of the Earth ground. And if you have a devices with different grounds, that leads to interference.

An example is a stereo system that "hums". This is a result of the chassis ground and the Earth ground being at a different potential. Or components having different ground reference points. It's also referred to as a ground loop. Assuming you had plugged such a device into your UPS and then pulled the power, the results would not be pretty if you were to unplug the UPS to test it.

Stereo humming is one of the reasons that certain devices have a chassis ground ("fixed" ground) that is above the Earth ground to prevent issues from things like ground loops. There's a good chance in the medical profession that you encounter such devices which need protection from this type of interference.


That is correct, but the issue is not after it's on battery power or even before. The issue is the transition. During that instant you unplug the UPS is where the problem is. The ground was expected to be there by the UPS so that current can leave via the ground wire during the switch. Once you remove that path to the ground, that could leave through you or one of your devices. This is why you hear random stories of people's UPS blowing up when they do the unplugging test.

As to why the computer shutoff why you still had electricity in the office is simply due to overload protection built into the UPS. Almost all of them have it nowadays. If it's pulling too much power, it will shutoff to protect the device.

Gene is probably right with the first theory about the internal circuit breaker. If you look up the specs, you'll the APC 600 has internal circuit breaker with a reset button to reset the breaker on the UPS. Some UPS's just have fuses instead of the circuit breaker.