Why do UPSes not trip fast enough when a laser printer kicks in?

[Red Squirrel]

I've seen this issue many times. A laser printer plugged into the same AC leg as a UPS protected computer. When the laser printer kicks in, it causes a brownout on that leg. The UPS never reacts fast enough and the computer shuts down. Well I think it does not react AT ALL, given it's not really an outage, just a brownout. My old printer used to do this and I was lucky enough that the hallway plug was on the other leg so I used to plug it in that plug. Now my parent's is doing the same thing. It seems to be random as sometimes you can get away with it and it wont happen.

What is the solution to this issue? I'm thinking some kind of capacitor bank, but that would require a rectifier and inverter. Would be rather expensive I would think. What about an isolation transformer, would that do any good? I can't see how though.

I can't be the only one who has seen this issue before. What is a common solution?

 

[MagnusTheBrewer]

Three questions, why is your printer plugged into the UPS, why are you printing when the power is out and, is your UPS of large enough capacity to run both your printer and your computer?

 

[Red Squirrel]

It's not plugged in the UPS, but it's plugged in the same circuit as the UPS. So when the printer kicks in, the voltage drops momentarily when the fuser goes on and the UPS is not kicking in so the computer shuts off as it's not getting enough power for a second.

I caught it once with the volt meter and it dropped down to like 100 volts but it was only for like a split second, so not sure how often meters sample or how accurate that reading was given it's such a fast dip.

Also, I'm pretty sure that circuit is on a GFCI, but I'd have to go check (it's not my house, it's my parent's) but I don't think that would do anything would it? It's not like it's actually tripping it.

 

[MagnusTheBrewer]

It's not plugged in the UPS, but it's plugged in the same circuit as the UPS. So when the printer kicks in, the voltage drops momentarily when the fuser goes on and the UPS is not kicking in so the computer shuts off as it's not getting enough power for a second.

I caught it once with the volt meter and it dropped down to like 100 volts but it was only for like a split second, so not sure how often meters sample or how accurate that reading was given it's such a fast dip.

Well the short answer is to run an extension cord from another circuit. The long answer is to update the wiring in your house. A printer and a computer shouldn't be an issue on a single circuit.

 

[Red Squirrel]

Well the short answer is to run an extension cord from another circuit. The long answer is to update the wiring in your house. A printer and a computer shouldn't be an issue on a single circuit.

That's what I'm thinking but pretty sure the whole basement there is on one circuit. Though I wonder if it's maybe just a brownout local to the power strip. So maybe if I plug the printer directly into the wall or another plug I'll be ok?

The wiring is fairly new in that basement as it got done maybe 15 years ago, so it's all standard romex, proper awg to code, etc...the contractor who did it builds houses as a living so he knew what he was doing when it was done.

I guess I'll start with plugging it into another outlet to rule out a local brownout at the power bar.

 

[MagnusTheBrewer]

You've got to have more than one circuit running to the basement. Generally there's one for the lights, one for each appliance/furnace/ac etc. Plug some lamps into different sockets and test with the breakers.

 

[Red Squirrel]

Oh I'm sure there's some, but pretty sure that room is all one circuit. I'll have to check when I go there though.

 

[Jovec]

Are you sure your UPS is working correctly to begin with? Pop the fuse/unplug and verify.

 

[Anteaus]

Check your circuit and breaker. Your printer shouldn't be pulling near enough amps to dim the lights let alone cause a brownout. I've seen this sort of thing happen when there was corrosion at the breaker and it didn't have enough surface area left to properly conduct. I had a very similar problem for a long time before I realized the problem was at the panel.

As to your UPS, if it's not switching fast enough to catch your PC either it is undersized or something might be wrong. The batteries only last 3-4 years so if it's older than that you might need to look into replacing the batteries or the whole unit.

 

[Red Squirrel]

The UPS is brand new and worked fine when I tested it, but I guess it would be worth testing it again just to make sure it is indeed working properly.

I'd check at the panel, but their panel... let's just say it's far from being legal. Need a hockey stick to reach breakers, let alone being able to open it and look inside. They're suppose to fix that at some point though.

I'll have to experiment more once I go over to check it out. I just find it odd the UPS is not switching fast enough for a brown out but works fine for a complete blackout. Is there some kind of sensitivity setting I may need to adjust? I recall reading something about a special command prompt you can get into on APCs. You can adjust the float voltage and stuff like that, but wonder if there's also a sensitivity setting.

 

[MagnusTheBrewer]

The wiring is fairly new in that basement as it got done maybe 15 years ago, so it's all standard romex, proper awg to code, etc...the contractor who did it builds houses as a living so he knew what he was doing when it was done.

I'd check at the panel, but their panel... let's just say it's far from being legal. Need a hockey stick to reach breakers, let alone being able to open it and look inside. They're suppose to fix that at some point though.

:whiste: One of these things, is not like the other one. :whiste:

If everything in the room is on the same circuit, you may just be overloaded. Get that contractor to do it right.

 

[max347]

Your computer goes out? Very weird. I have my desktop and printer on the same power strip. Sure enough, when I hit print my lights dim. But also, my computer does not go out

 

[Red Squirrel]

:whiste: One of these things, is not like the other one. :whiste:

If everything in the room is on the same circuit, you may just be overloaded. Get that contractor to do it right.

The panel is a whole other story, it's my parents' doing. They decided to install a cabinet right over it. So it's barely accessible. There's a small opening you can stick a hockey stick in to turn breakers on/off, that's it. If that contractor had seen that he probably would have told them it's against code.

It would be impossible to change the wiring now, it's a finished basement, and it's drywall everywhere, even the ceilings.

If ever I can gain access to the panel I will check to make sure the terminations are ok though. In fact I would not be surprised if a breaker is loose from being hit with the hockey stick lol. It's a terrible setup.

Regardless though, the UPS should be kicking in when it browns out, no? That's the main issue at hand right now.

Worse case scenario I can maybe put the UPS on another power bar and just tell my dad to flip the switch before printing, that should force the UPS to kick in as it will be a full outage and not a brown out.

 

[bryanl]

Voltage meters aren't good for measuring fast changes, so take a measurement under a heavy continuous load, such as a hair dryer, vacuum cleaner, or space heater. The safest method is by plugging one of those devices into a Kill A Watt. A drop of more than 2V indicates condition that must be repaired, such as a loose AC socket or wiring connection, and rear push terminals are the cause of many bad connections.

You may simply need a surge protector with a good line filter inside consisting of both capacitors and inductors. Plug either the UPS or the laser printer into it but not both. Line filters made of just capacitors are much less effective.

 

[who?]

Your UPS may not be set right. Did you install the software on the computer? This lets you adjust the settings. Did you get one with automatic voltage regulation? We used to watch a desk lamp blink at work to know if the printer was starting.

 

[Mark R]

Cheap UPS systems are "standby" systems. They detect a power failure and transition to battery power after about 10 ms of power loss. They also detect severe brownouts and treat these as power failure, but in order to save battery power for true blackouts, most ignore mild or medium brownouts.

It sounds like you have a marginal PSU in your PC which is shutting down during a brownout which your UPS is ignoring. There are other issues with PC PSUs - PC PSUs are only rated to maintain power for about 16 ms following a power failure. Most cheap UPSs will take 15-20 ms to transition, meaning that a heavily loaded PSU may exhaust its capacitors before power comes back.

Your options are:
1. Upgrade to a voltage regulating UPS (also called line interactive) or a double-conversion UPS.
Voltage regulating UPSs will detect minor brownouts/overvoltage and will use electronic power conversion to boost/reduce the voltage to the load without switching over to battery mode.
Dual conversion UPSs run on battery at all times (except in maintenance mode or under fault conditions) and continually top-up the battery from the mains supply. The voltage to the load is precisely regulated regardless of input power conditions and there is no break in power delivery in the event of mains power failure, as the load is already on battery power.

2. Upgrade the PSU to a higher wattage model. PSUs are required to provide 16 ms power at maximum load. If your PSU is only loaded to 50%, then you would probably get about 30 ms. And if only loaded to 20%, you may well got 60 ms of "carry over" power.

 

[Jeff7]

Voltage meters aren't good for measuring fast changes, so take a measurement under a heavy continuous load, such as a hair dryer, vacuum cleaner, or space heater.
...

Time for a faster meter. :sneaky:

What kind of UPS is it? I've been using Cyberpower UPSes for a few years now. They're still consumer-level, but they get the job done. Some of them are also very sensitive, and will easily trip to the battery, though I've also usually gotten the ones with some of the automatic voltage regulation circuitry.

That, coupled with decent brand-name power supplies in the computer. They've usually got beefier caps on the input, and wider input ranges, so they can handle some voltage dips by themselves.

 

[Red Squirrel]

This is the UPS they have: http://www.apc.com/products/family/index.cfm?id=27

The 1000va model.

Is there any settings I can change perhaps? I suppose the other option is getting a higher end PSU. I built that machine and I usually don't cheap out on the PSU though... What are good brands now days?

I suppose the other option is to have a separate power bar for the PC and have them turn it off before they send a print job. It's only the initial "kick" of the printer that causes the brownout. Once it's printing it's ok. Though that's only really a bandaid solution.

 

[Jeff7]

I haven't seen any kind of switchover settings that can be changed. I'd think that a UPS would be designed to switch over as fast as it reasonably can - likely that 16ms time that Mark mentioned. (1/60Hz = 16.67ms)

I'd also say that the power supply in the PC might not be terribly well-made, or maybe it's damaged in some way. One way, among many, to cheap-out on power supplies is those input caps. You can also include any filtering that might have gone ahead of that stage.

 

[Mark R]

UPSs should switch over within 16 ms - some of the cheaper ones may be a bit slower - so, in theory, there shouldn't be a problem.

One thought I've had is that the UPS you are using is a square wave output. Generally, this type of output is poorly tolerated by modern PCs, and many PSUs (e.g. "energy star" or "80 plus" rated PSUs) will not be able to operate on the very dirty and distorted waveforms that this type of UPS produces.

Sometimes, things work, but the switch over can be unreliable - especially, if the switch over is preceded by a brown-out, rather than an instant switch over due to power failure. Alternatively, it could be an issue with the voltage regulation on the UPS - again, this usually produces a terrible power waveform, which can disturb many PSUs.

Before replacing the UPS or PSU, try moving the printer to another outlet. Power strips and extension cords are notorious for adding lots of resistance which can cause very severe brownouts on the power strip. Moving the printer to another wall output will reduce the resistance in its circuit and may make the voltage dip less severe.

 

[Red Squirrel]

If I unplug it, it works fine. It's only when the printer kicks on. It's already plugged into another outlet, but it's on the same circuit, so does not really do much. There's no other outlets around.

I almost need some kind of capacitor bank but I don't really want to spend lot of money, it's not my setup. If it was I'd just run another circuit that's on the opposite AC leg and call it a day.

Another thing I will try for shits and giggles is bypass the GFCI plug. I can't see how it would do anything (it's not actually tripping) but I suppose it's worth a shot. Not really sure what they circuit is GFCI protected anyway.

 

[bryanl]

Another thing I will try for shits and giggles is bypass the GFCI plug. I can't see how it would do anything (it's not actually tripping) but I suppose it's worth a shot.

Will that be easier than an effective solution, an AC line noise filter?

 

[Mark R]

Will that be easier than an effective solution, an AC line noise filter?

I doubt that either bypassing the GCFI or adding an AC filter would be remotely effective.

Neither will help, because the problem is neither ground leakage, nor AC noise.

The problem is a brown-out. Actually, it looks as if the OP's UPS is a voltage regulating UPS. It should be able to correct the brownout, and if it can't it should switch to battery. The UPS is defective and should be replaced.

 

[Red Squirrel]

Will that be easier than an effective solution, an AC line noise filter?

Just as easy, and free.

This is a brand new UPS, bought it only a few months ago. Damn so is it faulty then? Is APC not the cat's ass anymore? Should I look at Tripp Lite? I do have a Tripp-lite inverter-charger at home (more expensive model) and it works great. Got two 100ah batteries on it and it will last for 4-5 hours.

I hate to tell them they need to spend more money though. Could it be a bad relay? I could always just swap out all the relays in it with higher speed ones or something.

 

[bryanl]

This is a brand new UPS, bought it only a few months ago. Damn so is it faulty then? Is APC not the cat's ass anymore? Should I look at Tripp Lite? I do have a Tripp-lite inverter-charger at home (more expensive model) and it works great. Got two 100ah batteries on it and it will last for 4-5 hours.

I hate to tell them they need to spend more money though. Could it be a bad relay? I could always just swap out all the relays in it with higher speed ones or something.

I've had old relays fail from burnt or welded contacts or a cracked solder connection with the PCB, but never a new relay. I believe all relays the size of those found on UPS boards switch in 8-16ms.

The APC may be faulty by penny pinching design, and my suggestion that line noise is at fault can be tested by plugging either the APC or the laser printer into a line filter.