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Posted by Doug Miller on June 28, 2007, 10:35 am
>I've been in my home almost 10 years and all of a sudden, a single
>circuit in my home started to flicker and intermittently power on and
>off (the breaker never tripped). I've done electrical work in the past
>when I finished my basement. The first thing I thought of was to
>replace the breaker. It's a Cutler Hammer twin (slimline) 15A breaker.
>
>After replacing it, the problem still occurred (so it was unlikely it
>was the breaker). After some diagnosising, I noticed that there was
>some arching ocurring in one of the terminals on the neutral buss bar.
>I tapped on the panel, and a small spark shot from the terminal. I
>turned off the circuit in question, and the arching and spark ceased.
>I then knew that the arching neutral belonged to the circuit in
>question.
Sounds like that terminal is a bit loose. Did you tighten it?
And is this copper wire, or aluminum?
>
>I found it odd that there are one or two ground wires on the neutral
>buss bar. However, the neutral buss bar is right on top of the ground
>buss bar. Don't they go to the same place anyway? Is this odd or OK? I
>know I've seen some panels where the ground buss is totally separated
>from the neutral buss.
It's OK, as long as this is your main panel. Neutral and ground are required
to be connected at the service entrance (main) panel, and required to *not* be
connected anywhere else.
>This neutral wire is sharing the same screw terminal on the buss bar
>with a ground wire from another circuit.
That is *not* OK unless the terminals are specifically listed for use with
more than one wire. If they are, it will say so on the label inside the panel
access door.
>I shut off the main breaker
>and screwed down the terminal firmly which fixed the problem. However,
>5 days later, it started happening again. No sparks fly when I tap on
>the panel, but there is slight arching in that same termAinal.
>
>Just eyeballing it, it looks like my neutral is a 14 gauge whilst the
>ground in the same terminal might be a 12 gauge which would explain
>why the neutral is not secured enough by the screw terminal. I am
>going to to shut off the main breaker do some housekeeping on the
>terminals making sure the same gauge wire is shared by neutrals in the
>same terminal.
Better still to use only one wire per terminal.
>1. Does it look like I've diagnosed the problem and I'm taking the
>correct measures to fix it?
Diagnosed the problem, yes. Correct measures to fix it, probably not. The best
fix is one wire per terminal (unless the terminals are specifically listed for
two wires).
>
>2. Why would this happen all of sudden after 10 years of living in the
>home? The terminal screw didn't seem all that loose when I tightened
>it the first time. I barely got 1/16 to 1/8 of a turn on it.
Copper or aluminum wire? This is VERY important.
>
>3. Is it OK for neutrals and grounds to share the same terminal on the
>neutral buss bar? Of different or same circuits?
As long as we're talking about a main panel, not a subpanel, and the terminals
are listed for use with two or more wires, that's fine. Since the neutral and
ground are electrically continuous in the main panel, there's no problem
electrically. Mechanically, you may have a problem attaching multiple wires
securely.
>
>4. Any other comments to add on what I've described?
If this is aluminum wire, you have to be *very* careful not to overtighten the
connections.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
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