Uninterrupted power supply or UPS is meant to provide electric power to the equipment in case of power outage. We often buy a UPS for our computer at home or install it at the office for Servers, Switches and other . If we have a printer at home, we connect it to the UPS without knowing any repercussions. Even most of the UPS manuals also comes with a caution to “not to connect the UPS to the printer”.
The printer I am referring to here is a laser printer since it is equipped with a fuser assembly that draws a large current when they are switched-on.
The normal ampere rating of a laser printer is between 1 to 2 amperes but when the fuser starts to warm up, the startup current shoots to ten times of normal current. The average temperature of this fuser assembly is around 200 degrees C. In order to melt(fuse) the toner powder, the fuser unit needs to maintain this temperature. So the fuser heats up on the periodic interval to not let its temperature down.
The average listed wattage of a laser printer is around 200 watts which may go up for high-end business models. But during the warming up of fuser, the power consumption jumps to 700 watts. If at home, you attach a computer and printer to a UPS, it may result in overloading of the UPS.
Some UPS systems come with extra surge protection sockets which do not provide any power backup to the equipment. Some people attach printers to theses sockets but this is also NOT recommendable since the power spike created during warming up of fuser can trip or damage the UPS or other computer system attached to the UPS.
In case you really want to put the printer on a power backup unit, you need to buy a UPS that is designed or sized to meet the power consumption of laser printers. APC recommends using a UPS that matches the maximum ratings (during fusing-warming) of the printer. You can use a minimum of 1.5KVa UPS (uninterrupted power supply) for a typical All-in-one Laser printer.