My Epson SP 2880 printer is plugged into a battery backup outlet on my APC UPS. APC does not recommend this but, instead, wants the user to plug it into a surge protected outlet that is not backed up by battery power.

Epson cautions against pulling the plug on the printer and says that you should always shut it down via the on-off switch. Obviously, a battery backup would prevent the equivalent of pulling the plug in the event of a power outage. I always turn off both the computer and the printer when I leave, so I would be able to manually shut down if the power goes out.

Any thoughts about the discrepancy between APC and Epson?

The reason for not using battery backup on a printer is because the power draw of the printer, when it is actually printing, can very quickly discharge the battery and possibly even damage the battery itself due to overheating. Plugging into a surge protected outlet that bypasses the battery would be no different than plugging the printer into a non-UPS surge protector. Since Epson, and for that matter any printer manufacturer, cannot guarantee the UPS actually has a battery bypass they are taking the safe route with their recommendations rather than risk being hauled into court because their printer caused the UPS to overheat and/or catch on fire and risk burning the house down. I have not read the instructions for every printer but I do know Epson is not the only one with that recommendation.

Your analysis is in agreement with the thrust of the statement in my Yamaha stereo receiver's manual that "The best ground is a metal stake driven into moist earth."

As you've suggested, the best way to prevail in the event of litigation is to advise extreme measures and let the consumer screw up on his own.

Edit: On the other hand, though, I wonder whether having advised a course of action that is so clearly impossible to follow in many circumstances would actually be a viable defense, or would it succeed by having placed the burden on the consumer?

There are two sides to this seeming contradiction. Joemikeb's comment covers a reason why APC (and other brands) might caution against using UPSes with printers. That said, not all printers are alike in power consumption, and many inkjet printers can be used safely when running on UPS battery power (within the limits of the UPS). Laser printers, however, should not be used this way, because of the power surge associated with preheating the fuser assembly on printer wakeup. In the past, CRT monitors would be excluded from UPS backup for a similar reason.

On the printer side there are non-electrical considerations. Among other things, turning off a printer with its on/off switch returns the printhead to its resting position, which protects the ink nozzles from clogging by drying out. This is particularly relevant to Epson printers, which (used to) have a fixed printhead, instead of one built into the ink cartridge. Fixed printheads that get irreversibly clogged render the entire printer useless. 'Cartridge printheads' are much cheaper to replace, should that happen.

Why did I say 'seeming contradiction'? Largely because potential problems can be minimized if not avoided altogether. When UPSes are only used for qualifying equipment whose power consumption is within their capacity, there is only an issue when a printer is ON, and NOT hooked up to a UPS when the power goes out. In those cases it suffices to power cycle (on/off) affected printers to park their printheads properly when power returns.

Thanks to all who replied. My major concern was having damage to the printer if the power is cut off. If that happens, I'll follow alternaut's advice and cycle the the printer on/off to park the heads when power returns.

To date, I have not had an issue when an outage occurs; I simply shut everything down manually. If the printer is in the midst of a printing cycle, that could complicate things but I haven't yet had that situation.

I try not to use the computer during bad weather but, to tell the truth, I have experienced more outages on sunny, calm days than during storms. Go figure.

First, electronics must never be damaged by power off. In fact, I challenge anyone to cite electronics damaged by a power loss by citing the component at risk. An international design standard from over 40 years ago was quite blunt about all voltages down to zero. Stated in all capital letters: No Damage Region.

Now, if its print head does not park, then ink jets may dry. Require cleaning. What electronics part is damaged? None.

Second, "dirtiest" power comes from a UPS in battery backup mode. Power so 'dirty' as to be potentially harmful to small electric motors and power strip protectors. That same power is ideal for electronics. Most will not discuss this due to advertising that misrepresents that 'dirty' power as 'pure sine waves'. A myth easily created when one 'knows' without first demanding spec numbers. What is at risk due to 'dirty' power?

A UPS is not recommended for a laser printer. In battery backup mode, a UPS outputs power so 'dirty' as to be potentially harmful to small electric motors. That becomes obvious once one learns to ignore hearsay and always demand numbers. UPS manufacturers hate to discuss this. Otherwise urban myths about 'power conditioning' will not increase sales.

UPS only keeps a computer and printer operational during a blackout. Do you need that?

I don't need or want to continue using the computer during a blackout. My only concern is to avoid a sudden, catastrophic shutdown that could damage the hard drive(s) and save changes to files. Therefore, I want the UPS to provide power that lasts long enough to save open documents and shut down safely.

Sudden power loss is how all disk drives shutdown without damage. No disk drive (even in the 1960s) is warned, in advance, about a power off. Does not matter whether power loss is due to a normal shutdown or the loss of a nuclear power plant. To a disk drive, all power downs are sudden and without warning.

A UPS does data protection. Temporary and 'dirty' power so that unsaved data can be saved. A UPS does not protect or preserve hardware - its primary purpose. 'Dirty' power from a UPS is made irrelevant by superior protection already inside electronics. Motorized appliances may be at risk due to 'dirty' power.

Power off does not harm electronic hardware. A statement that agrees with what APC and Epson stated. Laser printer should not be powered via that type of UPS.

I had always thought that a proper shutdown caused the drive head to park before shutting off, preventing the head from contacting the disk and possibly gouging it. Are you saying that the equivalent of pulling the plug on the drive does the same thing and is safe?

That's what I've always thought.

Westom is right: modern disk drives use voice-coil head actuators and don't require 'wall' power to park their heads. Instead they use springs and rotational energy to do that. See Hard Disk Drive Myths Debunked for some details.

Shutting down the drive does two things:

1. It allows any write operation to the drive to complete so that the volume structure is not left in an ambiguous state. However, one of the functions of Journaling is to provide a mechanism for automatic recovery from this problem the next time the system is booted.
2. It parks the head, but almost any hard drive built in the last 15 to 20 years has a spring loaded mechanism for mechanically parking the head in the event of a power loss.

With modern drives the biggest risk for crashing the heads (gouging the drive media) is from mechanical shock — falling off the desk etc. — and more and more drives are built to prevent that from happening. That said, it is good practice to "dismount" a drive before disconnecting or powering it down. A part of the normal OS X shutdown process is to dismount the drives.

Ah! Very informative! Thanks for the link and to Westom for debunking the myths that I had believed for so long.

Ditto.

Unfortunately, it is still possible to lose data, even with journaling enabled, if a hard drive loses power suddenly. Journaling helps make sure the disk directory isn't corrupted, but it is possible that data which have just been written to the drive are still in the drive's write cache and haven't been recorded onto the disk yet. If that is true, sudden power failure will cause the data to disappear into thin air.

When I was first worked on drives, an unexpected power loss would literally throw your entire hand out. When first observed, I thought that was dangerous. Even that power loss was not harmful - to hands.

Drives have always worked that way. Once the drive sees power dropping, plenty of power remains inside to completely anything that must finish. Even disk drives that used motor oil had enough power to finish.

Although hardware can never fail on a power loss, some early file systems might lose data. FAT filesystems were a notorious early example. If a file save was interrupted to an FAT filesystem, then a new file would be lost. AND (worse) a previous copy of that same file also might be deleted. FAT filesystems explain those 'refuse to die' myths. With HPFS, NTFS, and other filesystems (ie 1990), filesystem problems were eliminated. If a file was not saved, its previous version was restored.

Power loss, to computer hardware, takes forever. Even its power supply is required to keep operating for a long time after power is lost. Therefore a UPS switching from AC mains to battery (a period of no power) results in no computer interruption.

an inkjet won't draw enough serious power to be a problem on a ups, it won't affect runtime much even. Now a [b]laser[b] printer on the other hand, should only be plugged into the "surge only" outlet on your ups, they draw way too much power to heat up their drum and will either shut down your ups for current overdraw, or will suck down the battery very fast if not idle.

Well, not always. I once experienced a power failure with a PDP-11 using DEC RL-07 platter drives.

One of the drives survived. The other...err, didn't. The heads crashed into the spinning disks, completely destroying them and carving a furrow in the disk surface nearly half a millimeter deep. You wouldn't believe the noise it made.

Sounds like a circular saw, doesn't it?

I saw a similar drive on a PDP8 throw the head and platter shards clear across the room. Miraculously none of us in the room were hit by the flying debris but the back of the rack mounted PDP8 took a severe beating.

Were those glass platters? and it threw the heads too? wow. pictures?

The PDPs used aluminum platters coated in ferric oxide. They were typically 15 or 16 inches wide, depending on the drive type, and placed inside a machine roughly the size of a washing machine with a huge drive motor and a head positioning solenoid about six inches in diameter, so it wasn't uncommon for catastrophic failures to throw shards of the drive mechanism and/or little bits of aluminum all over the enclosure. I never witnessed a containment failure that sent debris outside the drive itself, but I've certainly seen catastrophic failures that throw bits of metal all over the inside of the drive.

I may be getting a tad off-topic here, but your description of old-time hard drive failures resembles catastrophic failures of scientific (ultra)centrifuges. I once saw the aftermath of a (presumably unbalanced) rotor crash, which sent debris through two adjacent concrete walls. Fortunately nobody was hurt, as the accident happened after hours, and long-duration centrifuge runs are typically scheduled overnight.

I wonder what really happened to the Iranian centrifuges as a result of Stuxnet.

In contrast to liquid centrifuges, it's hard to unbalance ultracentrifuges used to enrich uraniumhexafluoride gas by tinkering with their gas load, but it appears that Stuxnet affected the stability of running centrifuges by rapidly varying their spin rate in the Iranian nuclear facilities at Natanz, and in so doing it reduced the efficiency of the plant.

It turned out DEC was going around our plant routinely replacing the disk cartridges in the various drives. The cartridges had been cleaned by a subcontractor that had a mis-calibrated head alignment device causing the heads to crash on the surface of the platters. One of our techs realized what was happening and stopped DEC from installing the rebuilt cartridges but not before eight drives on eight different PDPs had spectacularly self-destructed. As I recall those were 50 MB cartridges costing roughly $45,000 each and that does not count the thousands of engineering man-hours we lost waiting for the destroyed drives to be replaced and reloaded.

I've read at least a few accounts of BIG old drum hard drives suffering catastrophic failure. Usually the brake seizes unexpectedly. These things were the size of a washing machine, and had a ferrous drum about the size of the basket in them, that spun about as fast as your clothes washer does when it's on "spin". Think of all the inertial energy in a heavy ferrous drum spinning that fast.

Now, very suddenly, attach it to its enclosure.

Those things were usually bolted down, but not for that. More to prevent them from 'walking' around when spinning. Those little floor braces were no match for all those joules of energy. In rare cases you might find yourself being chased by the unit, as it tumbled on its side violently until the brake finally fully caught and the drum came to a stop.

Too bad recording surveillance cameras weren't around back then, I'd love to actually get to see one of those incidents.

Inertial mass can add up pretty quickly even when the moving bits aren't all that heavy.

I worked for the first place in Florida that had a color laser copier back at the start of the 90s. The first batch of color copiers on the market retailed for $30,000 and up, and were extremely rare; we would routinely get people to pay $15 to $30 *a sheet* for color copies and computer output. (The place I worked shelled out another $30,000 for a gizmo that would attach the copier to a computer, allowing us to do something that most people could only dream about--make printouts from a computer in full color.)

Canon spent quite a bit of time tinkering with the design of the first primitive color copiers, trying to speed them up. The very first ones had four big drums made of thin transparent plastic, large enough for an 11x17 sheet of paper to wrap around, and a tricky mechanism to pass off the paper from one to the next so that the paper could come into contact with each of the four toner/photosensitive drum assemblies.

As you can imagine, they were quite slow by today's standards, taking over a minute to make a letter-sized photocopy and several minutes for an 11x17.

When they tried to speed them up, the early units had a habit, if the paper misfed, of throwing bits of mechanism all over the place. If the paper jammed, the computer would stop the mechanism, but the feed drums spun quite quickly. Occasionally, the delicate mechanism would break on a misfeed, and then the service guy would come in and spend a few hours elbow-deep in the copier, muttering about inertial mass.