[londons_explore]

Laser printers use a lot of power for a few seconds when coming out of standby.

Part of the printing process involves passing the paper covered in toner through a hot roller, to fuse (melt) the powder toner (ink) onto the page. That roller has to be up to temperature to print. It is normally heated by a powerful (ie. 1 kilowatt) light bulb inside a hollow roller. Sometimes if you peek through the vents in the printer, you can actually see the light it makes.

The light bulb is pulsed on and off to maintain the right temperature - but when coming out of standby it is solidly on for ~10 seconds. Manufacturers want their printers to warm up from standby quickly, so they put very powerful heaters in them, even though the steady state heat requirement isn't awfully much while printing.

[notatoad]

Running a printer off a 2000W gas-powered generator, it always gives me a little chuckle to hit print and hear the engine rev.

[actionfromafar]

Id THAT what that light is?! It always bothered in the back of my mind. It didn’t look very laser-y to me. Especially since the laser was supposed to be infrared.

[dtgriscom]

This is why you never put a laserprinter on a UPS.

[dismalpedigree]

Wait. Why? My laser printer is on a UPS. What is the problem I am not aware of?

[KolenCh]

It would becomes a power event on the UPS.

Not only you should not plug it in a UPS (the initial surge when a laser printer is on would likely surpass the power limit of your UPS too), a laser printer and an UPS should not be under the same circuit breaker. I know because due to a limitation to where I lived before, I have to put both under the same circuit breaker. Every time I print something, it is a power event (where I can hear that the UPS temporarily switched to battery powered mode.)

[Loic]

My UPS has a plug for the printer. It does only surge protection. This is convenient to have the full IT equipment of the office protected with just one box.

[KolenCh]

Laser printer is known to cause a surge event too. Normally there's a limited amount of surge protection available and routine surge would gradually used up the pool.

However, surge protection may not be as important. I heard an argument that it is basically snake oil (because an actual surge would normally be much more powerful and beyond a typical capacity they have, and some causes fire.)

[masklinn]

Does your UPS have a plug for laser printers, or just for printers?

It might be assuming an inkjet, which have much lower power draws: an inkjet will draw maybe 50W. A laser printer are generally in the mid-hundreds at least and some models can get into the high hundreds to low kW, you need a pretty heavy UPS to handle that and still power other systems.

[Loic]

For laser printer, it is specified on the plug. It protects only against power surge coming from the utility provider. It does not provide power to the printer, this is just a protection if your house is hit by lightning.

[vGPU]

Mine will always trip the alarm. Voltage draw too high.

[masklinn]

Surely it’s current draw? Wouldn’t the printer always operate at line voltage?

[nbernard]

Depending on your supply (for instance in an old house), the printer current consumption can cause a voltage drop on nearby circuits, and this voltage drop can in turn trigger the UPS.

[anonomousename]

Yes. The voltage alarm in this case would be the voltage dipping too low (voltage sag) due to high current.

[ambicapter]

What will happen to the UPS? A lot of discharge cycles?

[dbrueck]

I think the idea is that you have other stuff on the UPS too, and you'd prefer that stuff stay powered during an outage, but if your printer is on the UPS, it'll chew up all the power.

[Baeocystin]

It's more that consumer-grade UPSes will all trip due to overload as soon as you hit print.