I have a home office with a copier, laser printer, UPS, and a computer.
Only the computer is plugged into my UPS. When I turn on the copier or
laser printer, or when either one powers up from hibernate mode, the UPS
briefly clicks on. The house is only a few years old and the circuit is 15
I spoke to the electrical contractor. He simply said that if the circuit
breaker does not switch off, there is enough current and suggested
contacting a electronic equipment specialist.
I guess this has something to do with the voltage dropping when the machines
are turned on, but I am concerned this may damage or shorten the lives of
the equipment. Does anyone have any solutions to the situation, or is it
not an issue?
Thanks for any help,
I think you are headed in the right direction. I would put a DVM in
same receptacle that the UPS is in and observe what happens to the
voltage level when the printer or copier is turned on. This not a
perfect way of determining a lowering voltage level, but it should give
an indication if it is dropping. If it is, I would look at all of the
connections for that circuit all the way back to the breaker. Any high
resistance connection would lower the voltage as more current is drawn.
I probably should add that I tried the equipment on a 20 amp circuit; it did
trip the UPS. So I guess that means it is not a problem with the power
coming into the house. (The room with the 20 amp circuit cannot be the
I am not sure I fully understand the above statement. If you tried the
computer and ALL the other equipment on another circuit and still had
the same problem, it still could be you are lowering the input voltage
too much for the UPS. Taking the measurements would answer that question.
After all, it still could be a low voltage problem. It could be one
that effects ALL circuits. Such as input to the fuse panel.
Copiers and laser printers, when turned on, draw high
current - about 5 amps typically - (to heat the fuser)
for a short period of time. This causes a voltage drop
in the wiring. There *will* be a voltage drop, even if
your wiring is 100% perfect. That is normal. When
plugged into the same circuit, your UPS will "see" the
voltage drop. The UPS will click on, depending on how
much the voltage drops and for how long, and on the UPS
Your situation may not indicate a problem. Typically,
it is advisable to run laser printers/copiers on a
separate circuit to avoid the annoyance that the periodic
voltage drop may create. For example, a light fixture
plugged in to the same circuit may dim periodically
as the laser or copier re-heats the fuser. So much
If the voltage at the receptacle drops by more than 3%,
then the wiring and the total load on the circuit should
be checked. The drop is computed based on the voltage
measured at the service panel minus the voltage measured
at the receptacle.
Check the back of your UPS. It may have switches to make it less sensitive
to voltage fluctuations. Computer supplies aren't affected buy even moderate
fluctuations so should not be an issue. We one lost a phase, computers were
running 75 volts. I asked everyone to shut the computer off because that is
hard on the supply to operate under that condition for an extended amount
I have an interesting update. Haven't tested the voltage yet, but it makes
a difference which outlets I use even though they are on the same circuit.
In my testing so far, if the UPS and computer are at an outlet farther than
the copier is from the main switch box, the UPS trips when the copier is
turned on. If the copier is farther away than the UPS and computer, the UPS
does not trip.
My solution may be to move the copier to the end of the circuit. I hope the
voltage drop does not cause any damage to the copier. What is a safe
voltage drop for electronic equipment like a copier or laser printer?
Copiers and laser printers can draw a fair amount of current when their
heaters kick in.
But even at that, the voltage dip shouldn't really be all that bad.
You *might* have a loose/bad connection in that particular circuit (you
mention in another reply that the problem doesn't occur on another circuit).
This sort of thing could get worse over time and be a 'bad thing'.
If it's a 15 amp breaker in a fairly new house, I'll take a *guess* that
it's wired with 14 AWG wire. About how far away from the service panel is
the circuit? Other end of the house? Even at 80 feet, an 8 amp load should
only drop about 4 volts.
If you're handy with a VM, measure the voltage at the copier outlet with the
copier turned off, then turn it on and measure again. If the voltage drops
four volts or more, I'd say you have a problem that needs investigating.
Again, if you're handy with some home DIY projects and such, you can try
this. Find *all* the outlets on that circuit. *TURN OFF* the circuit
breaker. Go to each outlet, one at a time and do the following: 1) Check
with your VM that it really is turned off (safety first) 2) Remove the
cover and outlet from the box and check the wiring on the back. 3) If any
are 'stabbed' into a hole in the back, then insert a flat-blade screwdriver
in the slot next to the hole and release the wires. Take careful note which
wires were on which sides of the outlet. Connect the wires to the screw
terminals on the same side (wrap around the screw clockwise and get at least
3/4 of the way around) 4) make sure all screw connections are tight.
If you're not comfortable doing this sort of thing, hire a professional to
do it for you.
One friend was having problems with his stereo and TV equipment in the
living room. We checked all the outlets, and the connections in the service
panel. He was getting a large variation in voltage depending on how many
things he turned on (TV, VCR, stereo amp, turntable [oops, I'm dating
myself]). We *finally* tracked it down to an outlet in the baby's bedroom
that just happend to be on the same circuit. Behind the bureau, there was
an unused outlet with child-safety caps. When we went to check the voltage
there, we couldn't get the caps off because the plastic stabs had been
melted from the overheating. The wires on the back of the outlet were loose
causing a voltage drop and heating. My friend realised he could have had a
fire and was glad to find the problem. We replaced the outlet in the
bedroom and the appliances in the living room worked fine after that. Moral
is: Be sure to check *all* the outlets on a circuit.
It's only about 30 feet from the panel.
I guess I could measure the drop at any outlet in that circuit, correct?
In step 3, why do I connect the wires to the same side, and what should I
look for after doing these four steps?
Connect the wires to the same side that they came from!! Sorry, guess that
wasn't clear. Most outlets have three different colored screws. Some
copper/brass colored on one side, some silver/tin colored on the other, and
a green-painted one at the top or bottom. You don't need to remove the wire
from the green-painted one (but you can check it tight while you're there).
The black insulated wires should be on the copper/brass side, and the white
insulated wires on the silver/tin colored side. Best though is to note
where they are before you start and just be sure to put them back on the
same side. Or better yet, only do one at a time so they don't get mixed up.
If they are *not* 'stabbed' into the back, but are already under the screw
terminals, then don't remove them at all, just check each one is screwed
down tight. You don't need to break the outlet trying to put 250 ft-lb of
torque on the things, if you find a loose one, you'll know. Also check to
see that the wire is well under the screws and not just 'caught' by an edge.
Don't connect all the wires to one side of the outlet! I can see how what I
wrote could be misunderstood.
Well, *if* you were getting some significant voltage drops when the copier
started, and *if* the problem was a loose wire in any of the outlet wiring,
*then* when correcting/tightening the wires, you should not have a voltage
drop anymore when the copier starts.
P.S. One other place that could have a loose connection is where the
circuit is attached inside the main service panel. But going in there
should be left to someone with more experience in such work. It can be
P.P.S. As I said before, if you're not comfortable doing this, hire a
professional. But as most DIY folks can change out an outlet or wall
switch, you can probably do this. (REMEMBER TO TURN OFF THE BREAKER AND
CHECK EACH OUTLET DEAD WITH A VOLTMETER AS YOU GO)