Based upon the question: Should you plug a laser printer directly into a wall socket?
Given a normal US wall plug with two sockets, it is okay to plug a laser printer directly into one socket (with or without surge protector) and then plug the UPS into the other socket?
Will running the laser printer result in the voltage dropping and the UPS kicking into battery mode? Is there any difference if I use a wall socket somewhere else in the room?
Should a laser printer be plugged into the same wall outlet as the UPS?
Short answer: that makes no difference. Houses are typically wired so that all of the outlets in adjacent rooms are daisy-chained and connected to the same circuit breaker. Sometimes, several breakers are used to split the outlets so all of them do not go out if a breaker pops. A large draw in one plug could lower the voltage on all the other breaker's outlets, but I think it would also lower the voltage on every outlet in the whole house.
I wouldn't worry about it though. Appliances (in North America) are rated to run at 110-120V, and dropping from 120 down to 110 should be just fine, even lower "briefly". If you've ever seen the old incandescent light bulbs when a dryer/washing machine/electric stove is turned on, they can dim for about a second. It's nothing new and appliances are supposed to be designed to handle average things like that.
If your computer is on a UPS, that will protect it from such temporary "brownouts". The momentary voltage drop from a laser printer typically isn't enough to kick the UPS into battery mode but if it does, that's what the UPS is there for. That doesn't hurt anything.
Should a laser printer be plugged into a surge protector?
A surge protector will protect the printer from any high voltage spikes on the power line, which is valuable. It will have no effect on the printer's momentary high current draw or the effect of that on anything else.
Should a laser printer be plugged into the UPS?
Every UPS I've seen has some non-UPS / surge-only outlets that should be fine. They are not included in the power-rating (VA/watts) of the UPS, which reflects the limits of what the battery can supply when in UPS mode.
However, you don't want to plug a laser printer into one of the UPS-protected outlets. This is discussed in answers from "Why shouldn't I attach laser printers or scanners to a UPS?". Typical UPSs for home use are designed to handle the power requirements for the critical components of your system, to give you enough time to shut down gracefully. Adding the power requirements of a laser printer to that of the other components may exceed the rating of the UPS, in which case it would shut itself down just when you need it. Even if it is within the power rating, it would greatly reduce how long you could operate on the battery, which might not provide enough time to close your work and shut down properly.
Circuit should be sufficient to support a UPS and printer. Printer should connect directly to a wall receptacle. Also power an incandescent lamp. If a powering printer causes the lamp to dim significantly, then get household wiring fixed. In most cases, dimming only indicates a poorly wired circuit. In rare cases, dimming indicates a serious human safety defect. Printer is not causing a problem. That printer is simply identifying a defect that should be located and fixed.
If a UPS is large enough to provide sufficient power to the printer, it is still a threat to that printer. Power from a UPS in battery backup mode (even when a UPS is many times large enough) is typically so 'dirty' as to be harmful to motorized appliances (ie laser printer). Same 'dirty' UPS power is still ideal for electronics because electronics are so robust. UPS should never power any small motors because a UPS outputs such 'dirty' power.
Peak power consumption of a laser is typically around 1000W. Average consumption is far less, but that peak (added to whatever else is plugged into it) may exceed the UPS's maximum power capacity. For example, my home printer a DocuPrint CM305 df uses 410W during continuous printing, but up to 1100W peak during warm-up - and 8W in deep sleep mode. Buying a UPS that will handle that peak power is overkill.
When a computer experiences a brown-out or black-out, it may end up with a corrupt disk, which will seriously inconvenience you. On the other hand, a printer at worst will stop in the middle of a print, causing a paper jam. After power comes back on and you've cleared the jam, the print spooler on the PC will usually re-print the job automatically.
