Put in separate circuit for laser printer?

[reader2580]

I have a color laser printer in my home office. I believe the lights and outlets are on the same circuit. The light blinks at a high frequency when the laser printing is warmed up and not in power saving mode.

I have Cree LED bulbs in the light fixture. Would those be sensitive to the laser printer, or do I just need a separate circuit for the laser printer? The printer is fairly new and draws a lot less power than older printers. The only things on the circuit are a laptop with monitor, laser printer, and light fixture.

This printer had no issues at my previous house, but lights and receptacles were on separate circuits.

 

[grizz_660]

There should be a sticker or nameplate on the printer somewhere showing electrical information ( voltage, amperage, power consumption , etc ). See what it is. Some printers do require a seperate cct, others do not. If it is over 10amps, you should look into a seperate cct.

It may have an effect on lights or other pieces of equipment if it is drawing a lot. Maybe that cct is already over loaded.

 

[ctfjr]

One possibility is the printer may be generating rfi (radio frequency interference) that is affecting the leds. The signals could be traveling right down the ac line. I had an old 'all in one' printer that when it started to scan or print the led bulbs in my study would blink.

 

[zmaxmotorsports]

One possibility is the printer may be generating rfi (radio frequency interference) that is affecting the leds. The signals could be traveling right down the ac line. I had an old 'all in one' printer that when it started to scan or print the led bulbs in my study would blink.

 

[ForceFed70]

I think you understand the problem.

You've got a laser printer putting noise on the line along with a LED lamp that's sensitive to noise.

Putting on separate circuits would likely help (test by using an extension cord) but may not completely solve the problem.

Also - I suspect you have an older printer. The old laser printers needed a lot of juice. Never printers are a lot better - might want to consider replacing.

Really doubt this issue is related to EMI (rather than line noise) but I suppose it's possible if the printer and lamp are located very close to each other.

 

[DenisG]

There are all sorts of warnings against putting a laser printer on an uninterruptible power supply (UPS) because the surge current can wipe them out. Some engineer did a study showing that a 400W (max) Brother laser printer (HL4020) can draw a 55A inrush current:
http://pdf.donrowe.com/laser_printer_startup_surge.pdf
Usually breakers can handle brief inrush currents (like motor startups), but if the light flicker bothers you, then you might want to install a separate circuit.

 

[reader2580]

The printer isn't more than five years old. The labled draw draw is 8 amps or about 920 watts at 115 volts. The light fixture draws about 40 watts and the PC and monitor draw about 200 watts max. A 15 amp circuit at 80% can handle about 1380 watts. I am about 200 watts under if you use 80%. If you use higher than 80% then I am really good.

I'm trying to figure out if the issue is interference or draw. It never interfered with lights at my old house, but they were separate circuits. I am pretty sure this outlet is on the same circuit as the light, but I need to check.

 

[larry4406]

Our HP laser printer at work tripped the outlets and we had to put on separate circuit. We used a 20A cause didn't want to do it twice.

 

[CNGsaves]

You're on right track OP that office should have a separate circuit for heavy demand item like a laser printer.

I've got lots and lots of equipment in office of older home (built in 1955) and my old school HP Laserjet 4 indeed DOES dim the lights when it cycles.

I'm planning on adding dedicated circuit or two for my office.

If I were in your shoes . . . . YES . . . I'd put in dedicated circuit(s) to office.
. . . . .AND . . . . while you're at it, put in dedicated runs for CATV, internet, & phone.

 

[wyliesdiesels]

The printer isn't more than five years old. The labled draw draw is 8 amps or about 920 watts at 115 volts. The light fixture draws about 40 watts and the PC and monitor draw about 200 watts max. A 15 amp circuit at 80% can handle about 1380 watts. I am about 200 watts under if you use 80%. If you use higher than 80% then I am really good.

I'm trying to figure out if the issue is interference or draw. It never interfered with lights at my old house, but they were separate circuits. I am pretty sure this outlet is on the same circuit as the light, but I need to check.

Have u tried plugging the laser printer into a noise filtered power strip?

 

[BillK]

r,
Do you have a heavy extension cord you can use to run the printer off a different circuit ? That should give you an idea.

 

[larry4406]

Our HP laser printer also does not play nice with arc fault breakers.

 

[reader2580]

r,
Do you have a heavy extension cord you can use to run the printer off a different circuit ? That should give you an idea.

I have several quality 12 gauge extension cords. I just need to remember to bring one in from the garage to test with.

My laser printer has no issues with arc fault breakers.

 

[reader2580]

It only took me nine months, but I finally tested this. The LED light bulbs do not flicker when I run a 12 gauge extension cord from an outlet on another circuit. Now I have to run a new circuit for the laser printer. The most expensive part will be the arc fault breaker.

If I was building this house new I would certainly wire it entirely differently. Lighting and receptacles would never be on the same circuit if I could help it.

 

[Brandon314159]

I have a laser printer in my basement area and while it can make a noticeable drop for things on the line when warming up, I wouldn't expect 'flickering'

You have a DVM or WattsUp meter to confirm voltage on the outlet when the laser is on? May have a weak connection somewhere upstream.

 

[R.Anderson]

I have a laser printer in my basement area and while it can make a noticeable drop for things on the line when warming up, I wouldn't expect 'flickering'

You have a DVM or WattsUp meter to confirm voltage on the outlet when the laser is on? May have a weak connection somewhere upstream.

It will pend on what you have for lights.

OP said he had LEDs, I expect LEDs to be more responsive vs CFLs and incandescent lights.

 

[wyliesdiesels]

I have a laser printer in my basement area and while it can make a noticeable drop for things on the line when warming up, I wouldn't expect 'flickering'

You have a DVM or WattsUp meter to confirm voltage on the outlet when the laser is on? May have a weak connection somewhere upstream.

I just bought a laser printer and have used it on different circuits.

It definitely causes lights to flicker during warm up and printing. And theres nothing wrong with the circuit.

 

[manwithtools]

I just bought a laser printer and have used it on different circuits.

It definitely causes lights to flicker during warm up and printing. And theres nothing wrong with the circuit.

Not unusual to see this with a laser printer during warm up. We have a new printer that does this as well. The old LaserJet 4 we had was even more prone to this.

 

[reader2580]

I had never seen this issue in my previous house with the same laser printer. That house had the outlets on separate circuits from the lighting. The manual says it is rated at 650 watts.

At college they had an old original HP Laserjet. That thing would dim the lights in the room if turned on.

 

[vtsoundman]

I just bought a laser printer and have used it on different circuits.

It definitely causes lights to flicker during warm up and printing. And theres nothing wrong with the circuit.

You're on right track OP that office should have a separate circuit for heavy demand item like a laser printer.

I've got lots and lots of equipment in office of older home (built in 1955) and my old school HP Laserjet 4 indeed DOES dim the lights when it cycles.

I'm planning on adding dedicated circuit or two for my office.

If I were in your shoes . . . . YES . . . I'd put in dedicated circuit(s) to office.
. . . . .AND . . . . while you're at it, put in dedicated runs for CATV, internet, & phone.

There are all sorts of warnings against putting a laser printer on an uninterruptible power supply (UPS) because the surge current can wipe them out. Some engineer did a study showing that a 400W (max) Brother laser printer (HL4020) can draw a 55A inrush current:
http://pdf.donrowe.com/laser_printer_startup_surge.pdf
Usually breakers can handle brief inrush currents (like motor startups), but if the light flicker bothers you, then you might want to install a separate circuit.

It is the drum/fuser in the laser printer drawing a slug of current from time to time - has nothing to do with it generating RFI if the printer is functioning correctly. The lights dimming are the result of the voltage dropping slightly on the line as the fuser kicks cycles on and off. The frequency, duration, and repetition of the cycling depends on the mfr of the printer.

These short fuser loads have a peak current (half of a line cycle) draw of anyware from 15A-40A and with an RMS draw of 7-20A will last for a couple of line cycles.

It is not recommended to put laser printers on res'd UPS because they are unable to handle the fuser loading - and a UPS will the worst possible thing a UPS can do -> 'drop the load'. The UPS will shut down to avoid overload & damage. If the UPS is designed correctly, it will not be damaged.

Humans are very sensitive to lights dimming - w/ conventional incandescents it takes a scant 3V for the human eye to be annoyed by voltage flicker/dips. Some see it around 2V (younger people and women especially.)

A laser printer will most certainly cause lights to appear as if they are flickering - the same is true for toaster ovens w/ SCR/Triac control of their heating elements.

A separate circuit will typically solve the dimming issue as most folks experience voltage drop on the branch circuit and not at the panel. If you have a soft grid/source, then you may experience it at the panel as well and a separate circuit may not solve the problem but should help.

I used to design UPS for mass production all the way up to datacenters.

 

[reader2580]

A separate circuit will typically solve the dimming issue as most folks experience voltage drop on the branch circuit and not at the panel. If you have a soft grid/source, then you may experience it at the panel as well and a separate circuit may not solve the problem but should help.

I tested the printer connected to another circuit and the problem went away so it is just the one circuit being affected and not the main. I am in the process of installing a dedicated circuit.

 

[ryanwc]

Re: Put in separate circuits for multiple laser printer?

If anyone is still watching this thread, I've got a related question.

I help organize early voting for an election office. Our new voting system gives people the option of making their selections on touchscreens, but they must print the results and feed the paper ballot through a scanner. The one scanner per site and the many touchscreens draw relatively little power.

But each touchscreen now requires its own laser printer. HP gives guidance - only 2 printers per 15A circuit. This would make a mockery of our early voting, since at some of our locations, we've traditionally placed 20+ touchscreens to accommodate the number of voters. There is no public building in our area with a room of 10 circuits, and it's not even really feasible to bring that scale of power in.

My suspicion is that the HP guidance is based on a more typical usage pattern, where if you have, and need, 3 or more printers, you likely need them because you print a lot. And so there is the chance that at times, you'd be running your 3+ printers simultaneously for a period of time measured in minutes, or maybe longer, with some breaks.

Whereas in our usage pattern, even if we put 4 printers on the same circuit, they would each print a 1-2 page ballot once, taking 2-3 seconds, over the course of a 4-5 minute voting cycle. The odds that all 4 would be printing at the same time are quite low, and even then, the peak demand would last for 2-3 seconds, followed by a lot of circuit downtime.

My sense is that this would never be sufficient to heat up the wires nor to trip a breaker. I've tested that idea by sending simultaneous print commands to 4 printers at 1 minute intervals for several minutes, using a 15A surge protector with 15A circuit breaker, and didn't trip the breaker.

But I'm wondering whether anyone would way in with their thoughts and concerns.

 

[BillK]

Ryan,
I would call HP and see what they say to be certain. I am not sure how "modern" laser printers work and how they fuse the toner to the paper but when I worked for Xerox all of that was done with heat. There were heated rolls to fuse the toner to the paper and they were constantly held at temperature. If the modern printers are similar they might require quite a bit of current.

Your experiment may have worked with 4 printers but you referenced having 20 ? That is quite a difference.

 

[GRB]

I've been an HP dealer for 25 years or so. I would disagree with the comment about newer lasers drawing less power.

The original small lasers were built very heavy duty. We have seen general business units move to lighter duty, throw away units. There has also been a lot of very light units made to sell cheaply. These won't print on heavy card stock properly or print 1,000,000 pages. That is why they draw less power. Smaller, lighter duty units keep getting made that didn't exist before. The heavy duty business units draw almost as much as they always did. The electronics are a bit more efficient but the fuser is the big power draw and that takes the same as it always did.

Lasers were always a problem on a UPS due to the big inrush current to get the fuser hot by the time the paper gets to it. The tiny ones like the HP P1102 were dramatically better and this is what I used on mobile carts where we expected a UPS to run all the equipment on the cart. I recall their spec as 2a while printing so the inrush wasn't nuts. The new version of this is the M15 but I'm not familiar with that.

I'm pretty much done with HP Lasers after using 1000 or so. The new ones are built cheaply and have a bunch of fancy touch screens that want to sell you consumables and take FOREVER to turn on with all the **** they are loading, etc. etc. etc.

 

[ryanwc]

Your experiment may have worked with 4 printers but you referenced having 20 ? That is quite a difference.

Thanks for the reply, Bill.

Most of the sites have at least 2 circuits in the room used, and at larger sites, we can likely bring in additional power. But we've got 50 sites, and the idea of trying to get a 2 booths per circuit ratio everywhere is daunting, requiring interventions large and small at dozens of locations that we don't own.

If we can get away with a 4- or even 5-booth/circuit ratio, then many sites will need no intervention, since they're only assigned 8 to 10 voting booths; some will need an extension cord from another room; and the handful of sites with 16-30 booths may still need some electrical work, but not to the extent of trying to supply 8-15 circuits. We could probably get away with adding 2-4.

Yes, I think talking to HP may be our best route. I'm hoping our equipment vendor has a senior contact. Can't imagine trying to call customer service to answer this question.

 

[ryanwc]

I've been an HP dealer for 25 years or so. I would disagree with the comment about newer lasers drawing less power.

...

The electronics are a bit more efficient but the fuser is the big power draw and that takes the same as it always did.

For what it's worth, we're using a LaserJet Pro 402dne. Specs sheets say 548W on a continuous feed of 40 ppm, and 600W max draw. Does that seem realistic to people here? Or is there a brief peak draw that is significantly higher than 600W? And if so, how high might that possibly go?

I've seen references that suggest that some laser printers at times use as much as 4,500W (perhaps only for milliseconds). This is usually in a web-story about a printer that made the lights flicker until it was given it's own circuit. It seems to me that if such a printer can survive on its own circuit briefly drawing 4,500W, then my 4-printer set up, which still might never draw more than 2,400W, and then only briefly, might never trip a breaker.

Is that naive? Or incautious?

 

[ryanwc]

The vendor's proposed solution is putting every pair of printers on a CyberPower PR1500 UPS. If I understand, it's the "line interactive topology" that would allow this UPS to prevent peak draws from blowing building circuits.

But it's not actually clear to me that that's true.

And, even if it is, I'm worried about a vendor solution which recommends an off-label utilization of a UPS. CyberPower specifically says "no printers." It seems like any protection this UPS provided against blowing building circuits would only happen by instead blowing out the CyberPower first.

I might rather ask the building to flip a circuit breaker now and then rather than killing a $630 UPS every time 4 people press print at the same time.

But really, I just don't understand and don't have confidence in how the proposed solution would work. For anything that isn't nuclear physics, I prefer to understand at least the basics, rather than trusting someone selling me something. Can anyone shed light?

Thanks in advance.

 

[wyliesdiesels]

The vendor's proposed solution is putting every pair of printers on a CyberPower PR1500 UPS. If I understand, it's the "line interactive topology" that would allow this UPS to prevent peak draws from blowing building circuits.

But it's not actually clear to me that that's true.

And, even if it is, I'm worried about a vendor solution which recommends an off-label utilization of a UPS. CyberPower specifically says "no printers." It seems like any protection this UPS provided against blowing building circuits would only happen by instead blowing out the CyberPower first.

I might rather ask the building to flip a circuit breaker now and then rather than killing a $630 UPS every time 4 people press print at the same time.

But really, I just don't understand and don't have confidence in how the proposed solution would work. For anything that isn't nuclear physics, I prefer to understand at least the basics, rather than trusting someone selling me something. Can anyone shed light?

Thanks in advance.

The problem isnt the current during printing, the issue is the in-rush current during warm up.

I have multi function laser printer in my office and a 1500VA Eaton enterprise UPS. Sometimes if the voltage on the outlet is a bit low when the laser warms up, my UPS alarms and switches to battery.

Putting a printer on a UPS is a bad idea. Instead of the building breaker tripping, you could end up tripping the UPS breaker. small and medium UPSs are not designed for the large in-rush current that a laser printer draws much less 2 or more.

using a UPS for a laser is a recipe for disaster.

Have you thought of using inkjet instead?

 

[rlitman]

I've been an HP dealer for 25 years or so. I would disagree with the comment about newer lasers drawing less power....

I was certified to service HP (and Lexmark, Canon and serveral other brands of) laser printers back in 1996, not that that's relevant here.

I think that one of the most common misunderstandings of physics I encounter is the differentiation between energy and power.

Newer lasers use less energy, but draw more power.

Energy is the number that determines what you pay on your electric bill. It is represented by a total amount of something.

Power is a rate of energy user over time. With those facts in mind...

...HP gives guidance - only 2 printers per 15A circuit....

I'd say that HP's 2:1 guidance is reasonable IF and only if you are printing continuously (a worst case scenario). In your case, you are not, and I expect you will have a rather low duty-cycle (everything will have plenty of time to safely cool off between uses).

Here's a little background on laser printers. The ONLY part that consumes a significant electrical current is the fuser. Back in the early days, it would be a teflon coated oiled metal drum with a quartz heat lamp inside that kept it as hot as an iron. That "iron" melts the thermoplastic coating of the toner particles, fusing it to the paper.

Over the years, there have been improvements in energy consumption by reducing the thermal mass of the fuser and also by increasing the power input. Yes, more power into the fuser adds up to less energy. But that's only because more power means you can get away with less on-time.

So, nowadays, rather than continuously burning hundreds of watts to keep a large and heavy drum hot all the time, you're pulsing thousands of watts through a thin foil just for the seconds you need it to be hot. This is why the power requirements (and light dimming effects) of lasers are so extreme. For the instant that the fuser starts up, that printer is likely pulling more current than everything else in your house combined, just to heat it up to that melting point in the fraction of a second before the paper reaches the fuser. And the problem is even more pronounced in color lasers, which have to fuse each of the 4 (or perhaps 3) colors separately.

The good news is that modern laser printers (anything from perhaps the past 2 decades already), now use about as little power as possible, and that power is mostly determined by the paper speed. The melting point of the toner hasn't changed in all these years, so the idea is to apply just enough power to the heating element that the toner fuses at the same speed as it passes over the fuser. And that's good news for you, because you'll be fielding a bunch of relatively small printers, rather than a bunch of workgroup printers. These smaller and slower printers just don't require as much power to work.

Your circuit breaker is designed to protect your circuit's wiring from damage. It has what is called a time current curve that determines how much current is required to trip it. For a typical 20A breaker, the current required to "instantaneously" trip a breaker is usually a MINIMUM of 120A (with a current of double that being guaranteed to cause an instantaneous trip). That's a LOT of current, and while I think it might be possible for the perfectly coordinated startup pulses of four smaller laser printers to trip a 20A breaker, the odds of those all aligning in a bad way are pretty low. On the other end of the time current curve, while the breaker is designed to not ever trip below 20A, it also can run at 30A for a 20 perhaps as long as 120 seconds before tripping. So, if printing a sheet takes less than 20 seconds, you could safely run 6 printers on a circuit without tripping the breaker.

Based on this, I'd say that a rough guess of four printers to one 20A circuit ratio should work for you with few (if any) nuisance trips.

The vendor's proposed solution is putting every pair of printers on a CyberPower PR1500 UPS. If I understand, it's the "line interactive topology" that would allow this UPS to prevent peak draws from blowing building circuits...

For this, I have an emphatic NO! A Line Interactive auto-transformer will RAISE the current draw from the circuit when the voltage drops as it steps up the output. This is on top of the totally correct advice above about not running a laser printer on a UPS.

Also, something I didn't consider in the above analysis is voltage drop. In your case, voltage drop is your friend. That's because when the voltage on the circuit drops during the fraction of a second that a fuser is drawing a wild inrush current, the lower voltage limits the inrush current on all of the printers on that circuit, and the greater the voltage drop, the greater the effect. Basically, (pulling rough guess numbers out of my rear here for the sake of an example) if say one printer draws an inrush current of 35A, four together would be closer to 125A, and not the 140 that you'd get by simply adding them up. Now I'm not suggesting that you run laser printers on unnecessarily thin extension cords, but I'm sure your setup will be using extensions, and that too will help limit the inrush current. So those insane inrush currents measured when the printer is plugged into a circuit very close to the main panel will be significantly lower when on an extension cord (as it will be).

 

[ryanwc]

Thanks, all. This is very helpful. I still look forward to additional responses, but wanted to give my thanks now.

 

[ryanwc]

It's also worth noting that my question relates to early voting, a setting in which we have not yet used the new equipment. We did use the new equipment in precincts in a local election. We don't have large volumes in precinct, so each was served by 2 touchscreens (and 2 printers), running to a UPS that was required by law so that voting could continue in the event of a power outage.

In that setting, with 150 precincts voting, averaging 200 voters, we didn't experience any electrical faults. So it seems likely that the UPS can handle 2 of these particular models, with our usage profile, without much problem.

I'm more concerned about RLitman's point, that multiple UPS on a single circuit, each trying to even out voltage sags by drawing more current, would actually make a tripped breaker more likely.

 

[GRB]

For what it's worth, we're using a LaserJet Pro 402dne. Specs sheets say 548W on a continuous feed of 40 ppm, and 600W max draw. Does that seem realistic to people here? Or is there a brief peak draw that is significantly higher than 600W? And if so, how high might that possibly go?

I've seen references that suggest that some laser printers at times use as much as 4,500W (perhaps only for milliseconds). This is usually in a web-story about a printer that made the lights flicker until it was given it's own circuit. It seems to me that if such a printer can survive on its own circuit briefly drawing 4,500W, then my 4-printer set up, which still might never draw more than 2,400W, and then only briefly, might never trip a breaker.

Is that naive? Or incautious?

I used a bunch of the P2035, which is about the equivalent printer a few years before. Specs say 500w printing and it would cause problems run through the typical 850VA UPS I would use on a single office computer.

The M401 was the first HP printer I started to dislike. Of course the smaller MFP units were awful before that. I don't think I ever saw a M402 but one customer that has a number of P2035 wanted "the same thing" for an added employee desk. The closest was the M404 and it is poor. Stupidly expensive toner cartridge. You M402 falls in between but I think the Mxxx are the ones I'm not happy with.

Perhaps hook it thru a 850VA UPS and see if the UPS warning goes off?

 

[rlitman]

...running to a UPS that was required by law...

Yeah, you need to look into an alternative to laser. I just don't know what it would be.

Inkject printers that sit idle have a bad habit of gluing the print heads shut as the ink dries in them.

Dot matrix is not only objectionably loud (and the sound could actually present a security risk), but the ribbon, if you use a transfer style, presents a security risk. An endless cloth ribbon would be ok though. but if you're feeding this into an OCR system, the matrix printing could scan unreliably.

 

[SGKent]

I worked in IT for the state of California for 15 years, and retired last year. One of my responsibilities was about 150 HP laser jet printers the agency used.

1) this conversation does not belong here. It belongs between the person posting and the county commission on voting. Their IT department needs to be brought in. They need to speak with HP directly. More is at stake than "we thought this would work."

2) If you cannot meet the specs proposed by HP and the voting commission then you cannot just substitute a work around you heard about on a forum. You must test the solution in a real environment in a way designed to find fault if it is present.

3) I do not want to hear about the failure of the work around on the national news. Your concerns are real and valid, but the solution has to come from within your own organization. If this printer challenge applies to you, it applies to all other voting locations following the same rules too. It may even require a legislative change.

 

[rlitman]

I worked in IT for the state of California for 15 years, and retired last year. One of my responsibilities was about 150 HP laser jet printers the agency used...

Let's take this apart, shall we.

...1) this conversation does not belong here. It belongs between the person posting and the county commission on voting. Their IT department needs to be brought in. They need to speak with HP directly. More is at stake than "we thought this would work."...

Because THEIR IT department is always right? LOL. Here's a great read about $43 million spent on 10 years of IT work for what amounts to nothing:
https://www.newsday.com/long-island/politics/peoplesoft-nassau-software-1.38966575

"Trust but verify". If you blindly go in with what your IT department says, there's a good chance that you'll end up being adding one to the 169 municipalities hit by ransomware.

...2) If you cannot meet the specs proposed by HP and the voting commission then you cannot just substitute a work around you heard about on a forum. You must test the solution in a real environment in a way designed to find fault if it is present...

I don't disagree with real-world testing, but that requires a protocol and a competent engineering department. As for specs proposed by HP, well following those blindly is as dumb as blindly following civil service IT department advice. Because anything you see in a vendor demo always works, right? The vendor's goal is to enrichen their bottom line, and there's a clear conflict of interest here.

...3) I do not want to hear about the failure of the work around on the national news. Your concerns are real and valid, but the solution has to come from within your own organization. If this printer challenge applies to you, it applies to all other voting locations following the same rules too. It may even require a legislative change.

So looking outside of your organization for advice is bad? Way to go with the head in the sand civil service mentality! Kudos to your 15 years of service. It's great when you can just keep your head down, and if you somehow fortunately manage to keep out of the news, you eventually reach retirement.

"I've worked in the private sector. They expect results."

 

[ryanwc]

I don't take offense at SGKent mentioning that this forum, like any web forum, needs to be taken with a grain of salt, and that any solution would need to be vetted by all the interested parties and tested in a real-world setting.

I still appreciate what seems like a sound explanation from RLitman, and the real-world anecdotes that others have provided. Those things help me understand the situation. That will lead to a better outcome.

 

[slimpickins]

...
Here's a little background on laser printers. The ONLY part that consumes a significant electrical current is the fuser. Back in the early days, it would be a teflon coated oiled metal drum with a quartz heat lamp inside that kept it as hot as an iron. That "iron" melts the thermoplastic coating of the toner particles, fusing it to the paper.
...
So, nowadays, rather than continuously burning hundreds of watts to keep a large and heavy drum hot all the time, you're pulsing thousands of watts through a thin foil just for the seconds you need it to be hot. This is why the power requirements (and light dimming effects) of lasers are so extreme. For the instant that the fuser starts up, that printer is likely pulling more current than everything else in your house combined, just to heat it up to that melting point in the fraction of a second before the paper reaches the fuser. And the problem is even more pronounced in color lasers, which have to fuse each of the 4 (or perhaps 3) colors separately.
...

Just saw this thread and the answer by rlitman answers the cause of the lights flickering - it's more like a strobe effect. When I first encountered it roughly 10-12 years ago, it took a while to track down the cause which was a Brother fax printer. At the time I did some research and the cause is the new fuser technology used at the time.

We still have the printer, and the lights still strobe when the printer is printing. One thing to be aware of that I experienced with the "early model" new fuser technology printer was that if the printer ran out of paper, the strobe effect continued even though it wasn't printing, which means it was still keeping the fuser hot while waiting for you to add paper. This could have been for days!!!! The printer would not enter sleep mode when waiting for paper!!!!

In fact this is part of what led to originally tracking down the source of the strobe effect.

I would think that manufacturers have solved this problem in more recent iterations of the printer software - and perhaps there is a firmware upgrade for my printer that solves it. I'm sure we wasted a ton of power before realizing the cause of the strobe effect. It would also shorten the life of the fuser unit. It's just something to be aware of if you notice the strobe effect continuing after the printer stops.

Anyway, the strobe effect is most noticeable on lamps on the same circuit as the printer. It is slightly noticeable on circuits on the same mains leg of the panel. Not detectable at all on circuits on the other leg of the mains.

The idea to add a light duty extension to supply power to the printer to limit in-rush current sounds like it may help.

Cheers.