I have a house that's now 18 years old. I am the original owner. On one
circuit, I am getting intermittent loss of full power. This is manifested by
lights that go dim like when a motor somewhere kicks on. I have a UPS in
that room that beeps when this happens, but no tv's, clocks, etc. actually
experience a full loss of power requiring a reset. This happens anywhere for
0 to 20 times a day and can last from 5 seconds to 30 seconds and only on
that circuit. I have checked all the outlets and switches and replaced a
few. I have jiggled appliances and plugged and unplugged everything to see
if I can reproduce the effects consistently. I have checked the panel and
nothing seems out of sorts. I placed my hand on the breaker and it's not
warm. It's driving me crazy. Aside from calling an electrician in (the
obvious solution) can anyone help me track this down?
Have you checked things(loose connection, breaker seating, work out
breaker, etc.) inside the main panel? There is a little gadget you can
plug into an outlet to see if all is well. It'll tell missing ground,
neutral connection, reversed polarity, etc.
Any chance you have an aluminum wiring?
That sort of check doesn't mean much though.
If you think about how an electrical service is set up, it
might be easier to test it. Starting at the transformer on
the pole outside, your home is supplied with two circuits.
When you plug in a device it is essentially in series with
the entire loop all the way back to the transformer.
That loop is the key to testing it.
| outlet |
+---||---+ <--- Dimming never seen
| outlet |
| outlet X <--- Fault
| outlet |
+---||---+ <--- Dimming intermittent
| outlet |
+---||---+ <--- Motor plugged in here
That is a very very simplified diagram. If you put a
tester into the top outlet (closer to the transformer
than the fault), it will *never* show a problem. But,
if you put the tester into any outlet lower than the
fault, it *might* show a problem.
There will be no problem if either the resistance of the
fault or the current going through the fault is too
small. What causes your dim lights is the voltage drop
across that fault. Voltage = Current * Resistance.
So, the reason the tester won't see a problem is that it
does not draw enough current itself to make the problem
manifest, and it will show a problem *only* when
something else is triggering it. Motors cause lights to
dim because they draw a huge amount of current when they
start. The "fault" in that case could simply be that
none of the wiring is large enough to handle that much
current! In that case the fault is distributed all along
the entire circuit.
In any case, the lights dimming only happen where lights
are plugged in *after* the fault location. And then
only when enough current is drawn through the fault to
make it manifest.
So you could test it by putting a lamp into any of those
outlets, wait until you get dimming on other
lights... and *then* check to see if that lamp is dim
too, and from that determine which side of the circuit
from that lamp the fault location is on.
The first place you want to check is right at the
entrance to your electrical system, to determine if this
fault is in your house wiring or is part of the
utility's service. (It could easily be that your pole
transformer is overloaded, and the motor causing it is
an air conditioning unit in a neighbor's house!)
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) firstname.lastname@example.org
This sounds characteristic with a problem that manifests itself with
"backstabbed" devices. These have a small contact area in comparison to
screw terminals and the spring tension may vary with heat. You may want
to rewire each device using screw terminals.
Are you sure it only happens on that one circuit? Have you plugged
the UPS into another circuit?
You can call the power company and tell them you suspect a loose
connection on your incoming connections.
They will come out and tighten their connections at the meter and you
can tighten the connections at your panel while the power is off.
The service guy might offer suggestions.
That tells you it is not the UPS. That doesn't tell you that only one
circuit is the problem.
If it doesn't show up on another circuit, I would put my money on
backstabs as someone else has already suggested.
If it does show up again then it is mostly likely the service.
Yes. The load center commonly has aluminum wire. This is one of the
primary causes of a loose connection\\corrosion.
I feel that because the OP has the UPS on only one circuit it caused
him to suspect that single circuit. I suggested that he plug the UPS
into another circuit as a test.
Switching the UPS would be an easy way to rule out either/or. If it
works properly on another circuit then he would know he was correct
and track down the problem on the single circuit.
If the UPS does show bad power on another circuit the cause would then
be most likely the service from his main panel back to the meter base.
The power company will check their connections at the meter base (for
free) and shut down the power so the OP could tightening his panel
Depending upon the size of your electric service, the usage at the time, and
the distribution of the loads in the panel, dimming while motors are
starting can be perfectly normal. The fact that this circuit can remain in a
dimmed state for a prolonged period of time is not normal. You first want to
determine which motors are causing this problem, and which leg of your
service they are connected to. If the lights and circuits that are dimming
are not connected to the same circuit breaker as the offending motors, which
I assume they are not, you need to carefully examine all neutral
connections, especially those feeding the service at the service panel, the
main disconnect, the meter box, and the overhead service drop connection, or
underground lateral connection if applicable.
Go to the breaker box and swap the wire to the circuit breaker with another
breaker of the same capacity.
Does the problem move? If so, the breaker is the culprit. If not, at least
you know the problem is in the wiring somewhere.
Yes, that would make good sense. After rewiring all the affected outlets
from the "backstabbed" config to the screw downs, if it still happens I'll
try to switch out the wiring in the breaker box as you said.
I had this happen in my garage. I found it after some time. It was an
outlet but not one I thought it would be. Seems the electrician FORGOT
to tighten the screws in an outlet back down the line on the other side
of the garage. I was obvious once I pulled the outlet from the box.
You'll have to check them all THROUGHLY.
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