68
8
I have an FSP EP1000 UPS.
The User's Manual says:
CAUTION: NEVER connect a laser printer or scanner to the UPS unit. This may cause the damage of the unit.
Why is this restriction?
68
8
I have an FSP EP1000 UPS.
The User's Manual says:
CAUTION: NEVER connect a laser printer or scanner to the UPS unit. This may cause the damage of the unit.
Why is this restriction?
82
Updated
(Unless you accurately size the UPS for peak power requirements)
When turned on, Laser printers draw a high current to heat up their fuser roller. A typical UPS cannot cope with such a spike.
Descriptions of the problem by UPS manufacturers do not go into details.
The problem may be one or other of
Fuser temperature is up to 200 °C (392 °F).
From HP specification for LaserJet 3200
Power consumption 135 watts
During Printing: At nominal line voltage.
Model A (120V): Maximum of 700 W, Average of 210 W
Model AB (240V): Maximum of 625 W, Average of 210 W
Inrush Current: (Duration: significantly < 1 second)
Model A (120V): 23 A peak (20 deg C, from cold start)
Model AB (240V): 40 A peak (20 deg C, from cold start)
Note:
If we disregard power factors and other AC complications,
The inrush current is an order of magnitude larger than average operating currents.
In conjunction with other equipment, the 700W max during printing could overload a small UPS.
For example Belkin say
A laser printer or scanner draws significantly more power when in use than when idle. This may overload the UPS.
APC say
APC recommends a [UPS] that is sized for the maximum power draw of the laser printer as defined by the manufacturer. This is typically a 1500va or larger UPS. Even small laser printers can have very high maximum power draws due to the nature of the technology.
Anecdotal reports say
Laser printer usage is sometimes reported as causing voltage sags in power circuits such that lights noticeably dim in the building for a brief moment.
Here is an example of power used vs time.
From http://www.johndearmond.com/2008/08/04/laser-printers-and-inverters/
Does this answer apply to all outlets on an UPS, or just the battery-backed ones? – cp.engr – 2016-12-31T00:49:24.163
Confirmed. I had never given that any thought. When I plugged my laser printer into my UPS, it started beeping frantically. – Dennis – 2012-08-26T19:09:24.153
Hmm that's good to know. Thanks. (Both asker and you, RedGrittyBrick.) – Apache – 2012-08-26T19:34:58.083
2Nice informative answer. And good to know, thanks! +1 to both question and answer. – Indrek – 2012-08-26T20:26:42.957
5Curious, does this mean laser printers should only be directly plugged into a wall? (Meaning not a surge protector for example.) – blunders – 2012-08-26T21:16:26.603
1@blunders - No, plugging the printer into a surge suppressor would be fine, the surge inrush current isn't an issue there. – Fiasco Labs – 2012-08-26T21:21:35.913
4Why does the 240V model have ~2x higher inrush current than the 120V model? I'd expect the opposite behavior (equal inrush power). – Dan is Fiddling by Firelight – 2012-08-27T12:44:22.210
5
@DanNeely: I'm curious about that too, so I posted a question to electronics.se
– Justin ᚅᚔᚈᚄᚒᚔ – 2012-08-27T16:00:51.137what would happen if a laser printer is connected to a UPS and starts drawing a high inrush current? – ceiling cat – 2012-08-29T16:40:05.897
@ceiling cat: see quote in Question "This may cause the damage of the unit." (sic) – RedGrittyBrick – 2012-08-29T16:43:13.070
This isn't actually right. Note the inrush current is "significantly less than 1 second". That's charging capacitors in the power supply. Almost every switch-mode power supply will have that kind of inrush current—including both your computer and monitor. – derobert – 2012-08-29T20:31:36.047
See, for example, http://www.tomshardware.com/charts/120v-desktop-power-supplies/Inrush-Current,Marque_fbrandx72,2565.html ... A lot of those actually have higher inrush currents than the printer.
– derobert – 2012-08-29T20:36:15.227A Ricoh SP 4100 NL that I had attached to a UPS as a stopgap measure due to a power issue pulled 900W for a split second according to the gauge when it was powered on and sporadically thereafter. Some newer laser printers draw less power but still a lot (the HP we are trying to replace it with pulls about 400W under the same circumstances) It made the 850W UPS complain a little bit. – LawrenceC – 2012-08-31T21:17:16.763
@Alberto what question does it call for? I suspect we already have one on how to size an UPS, and "what does inrush current mean" is probably off-topic here... – derobert – 2012-08-31T21:18:19.883
@Alberto it refers to a previous revision of the answer. Check http://superuser.com/posts/466645/revisions and you can see the answer has been improved, to take into account the comments. That's definitely a good thing, with the minor downside that you have to check the edit history to understand all the comments.
– derobert – 2012-09-04T15:26:23.8478
Laser printers use a lot of power. At peak loads, laser printers may draw more power than the UPS can provide. As for scanners... I dont believe modern scanners use a lot of power, perhaps some higher-end multi feed scanners do...
I have a scanner that doesn't require any power supply at all apart from USB. (which is also not USB 3.0) – Display Name – 2014-04-14T18:08:15.553
1Im was not talking about simple desk scanners, but high volume enterprise scanners - ones that scan 100s of pages at a time – Keltari – 2014-04-14T18:22:40.637
5
Take a Canon imageCLASS LBP6300DN for example. The spec sheet (linked) says a maximum power consumption of 1120W. Let's try to find an UPS for just the printer, no other load. So maybe we look for 1200W.
You might first think, no big deal, grab a 1500VA UPS, more than enough. But VA != watts, and it turns out that (for example) an APC Back-UPS 1500 has a max of 865 watts. They assumed a power factor of .57. Finding a "consumer" ups above 1500VA is hard. So instead (as APC recommends) you look at the SmartUPS line. The smallest one you could use is a SmartUPS 2200, which will set you back $1000, more or less. I can't find anything in its manuals saying not to connect a laser printer, so APC is probably OK with this.
You could go with a Cyberpower UPS, they're usually cheaper, appears you'd need a PP2200SW, which you could have for around $500. Indeed, cheaper, but still pretty expensive. The manual says you "should" not connect a laser printer (or vacuum cleaner, wonder who tried that?).
You can connect a laser printer to an UPS. You just need to buy a really big (and expensive) UPS.
Thanks for commenting on this issue! I was just thinking about taking the PSU outside and connecting the vacuum cleaner so I could clean the seats. – Tom Anderson – 2016-04-27T10:30:07.993
+1 For the different consulted specs. "Should not connect a vacuum cleaner" (I'd upvote just for this quote!) – Alberto – 2012-08-31T19:46:52.193
3
Over and above the inrush issue (discussed above) there is also the consumption under load...
Unlike servers and desktops, printers are very rarely business critical, and users can usually do without them for the duration of a power-outage (maybe at a slight inconvenience).
On the other hand, UPS infrastructure is often spec-ed at the lowest that can be got away with, before adding extra hardware - so printers sucking out battery-reserves will limit the up-time of the rest of the network.
3You're forgetting that another key function of a UPS is to clean up 'dirty' power. An inexpensive UPS can be used to extend the life of much more expensive equipment by cleaning the power even if that UPS is unable to power the equipment during an outage. – Freiheit – 2012-08-27T17:25:57.320
1Lots of good answers about laser printers. What about scanners? Older scanners used fluorescent bulbs that might have the similar voltage/current requirements as laser printers. But recent scanners use LEDs. – David Poole – 2012-08-29T17:29:34.963