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Author Topic: Question for Elmer - Audio blip when turning off any power source in my house  (Read 4779 times)
K8AXW
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Posts: 3722




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« Reply #30 on: April 30, 2013, 08:37:00 PM »

UK:  This is a situation that shouldn't be considered "resolved" as soon as the problem is found and "corrected."

Many times when a conductor has overheated it changes the molecular structure of the copper wire and quite possibly the receptacle contact that it was attached to.

While your "fix" was probably fine, I would have been more comfortable if the receptacle was replaced and the wire end was cut off and a new section of the wire was used for connecting to the new receptacle.

At the very least, I would have checked it periodically for several months.  Perhaps this might be considered paranoia but I HAVE seen what happens to hot wire.
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W6EM
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« Reply #31 on: May 01, 2013, 09:12:47 AM »

UK:  This is a situation that shouldn't be considered "resolved" as soon as the problem is found and "corrected."

Many times when a conductor has overheated it changes the molecular structure of the copper wire and quite possibly the receptacle contact that it was attached to.

While your "fix" was probably fine, I would have been more comfortable if the receptacle was replaced and the wire end was cut off and a new section of the wire was used for connecting to the new receptacle.

At the very least, I would have checked it periodically for several months.  Perhaps this might be considered paranoia but I HAVE seen what happens to hot wire.

Copper wire that is used in listed branch circuit cables is soft-drawn or annealled soft copper.  The caveat is, in making connections via a connector, is that the conductor itself does not neck-down and lessen in cross-sectional area.  The resistivity of the base metal won't change much, if at all with respect to hardness.  Remember that the resistance is directly proportional to length and inversely proportional to area.  Ideally, in a compression connection, the connector metal "moves," and the conductor does not.  A screw, however, shouldn't be soft.  It needs to dig into the copper conductor and hold it firm.

You are right with your recommendation.  To be sure, change out the outlet where the screw and conductor were overheated.  The other thing that usually happens is that the PVC insulation close to the hot spot will exude anhydrous chlorine gas.  This will corrode bare copper and in extreme cases, turn it green and develop a blue-green "ooze" all over it near the hot spot.  And, the nearby insulation becomes quite crispy and ineffective in the process.

The nomenclature of grounded conductors is a tad confusing.  Back several editions of the NEC, they renamed the neutral or white conductor the "grounded" conductor.  Why?  Because it's connected at the service entrance to the "grounding electrode conductor" from the ground rod or other means of grounding and tied to the green or bare "equipment grounding conductor."  It's more confusing now because the white "grounded" conductor can and does very often have voltage impressed upon it beyond the common connection point.

73,

Lee
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K1CJS
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« Reply #32 on: May 01, 2013, 09:45:45 AM »

...replace every outlet and switch on that circuit with screw-down back-wired devices, and check the wire nuts to make sure the wires were twisted before being inserted into the wire nuts.  those two steps could get the high resistance piece out of your way forever....

All too often, outlets installed are connected simply by pushing wires into spring clip type connectors in the back of the outlet itself.  Although that type connection may be trouble free, just let the outlet get heated by a bad plug or connection, and that spring clip may lose its resiliency.

I do my own wiring (worked for an electrician in my earlier years) and when I replace outlets and switches I always strip the wire and use the screw connectors on the outlet/switch.  It's simply a better connection method, and one that can eliminate the type trouble you're experiencing--if those spring connection are the cause.
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KB5UBI
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« Reply #33 on: May 01, 2013, 11:54:24 AM »

Nothing to worry about; it's just the NSA bugs installed in your house.
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KB9YNB
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« Reply #34 on: May 01, 2013, 06:17:20 PM »

Slight correction:  The ground an neutral should be connected at the first disconnect after the meter.  If your breaker box is located far away from your meter, then you probably have a disconnect at/near the meter, which is where your ground and neutral will be bonded.

Not quite.  The neutral and the ground should be bonded together at the breaker box, and usually are by the simple method of directly mounting both the neutral busbar and the ground busbar directly to the metal breaker enclosure.  The meter socket does not have a 'ground' connection point, it has a 'neutral' connection point since the neutral is one three cables connecting the breaker box to the meter in a typical three wire 240 volt household system with the other two cables being the two opposite 'hot' phases of the system.  That neutral connection is the connection that is 'grounded', for all intents and purposes.

No, really.   If your "main" breaker box is not the first "disconnect" after the meter, then the ground/neutral will not be bonded there.  (It may depend on the age of your house and which NEC was in effect when it was built)

For instance, my house has a "disconnect" immediately next to the meter base, because my house breaker box is more centrally-located in the house.   The ground/neutral are required to be bonded at the very first disconnect after the meter, which is not *always* in the breaker box.

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K8AXW
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« Reply #35 on: May 01, 2013, 08:58:06 PM »

EM:  It has been my observation that on occasion an overheated conductor takes on a crystallized appearance and becomes brittle.  Natural vibration caused by anything from machinery running or the house expanding and contracting to the wire vibrating in the walls can cause this fragile looking wire end to simply break.

It isn't common but can happen.  I always sleep much better when I don't take chances with my wiring.  Again, this might be paranoia but I can live with that too.
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K1CJS
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« Reply #36 on: May 02, 2013, 04:02:29 AM »

...For instance, my house has a "disconnect" immediately next to the meter base, because my house breaker box is more centrally-located in the house.   The ground/neutral are required to be bonded at the very first disconnect after the meter, which is not *always* in the breaker box.

As does mine.  I believe that you've hit on it with your statement--
Quote
It may depend on the age of your house and which NEC was in effect when it was built.

One other thing,  I have never come across a feeder cable (meter to breaker box) that has both a neutral AND a ground cable in it.  They are both the same.  Also, I've never seen a breaker box that has both the ground bus and the neutral bus NOT connected directly to the metal of the box.  In any event, it's a moot point, since this is a ham radio site, not an electricians wiring site! 
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W6EM
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« Reply #37 on: May 02, 2013, 04:41:48 PM »

One other thing,  I have never come across a feeder cable (meter to breaker box) that has both a neutral AND a ground cable in it. 

That is because it is technically the service entrance from the utility into the main breaker or fused switch main disconnecting means.  The grounding electrode conductor and the utility neutral are tied together and at that point, the neutral becomes the "grounded" conductor.


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They are both the same.

Only at the enclosure housing the main disconnecting means.

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  Also, I've never seen a breaker box that has both the ground bus and the neutral bus NOT connected directly to the metal of the box. 

Apparently, you have never seen a sub panel downstream from a main panel.  When you purchase a breaker panel, the neutral bus is insulated for a reason.  Just that.  In case it is destined for use as a sub panel.  Usually, the manufacturers include a "grounding screw" which can be used to ground the bus to the metal can if it is going to be used as a main panel.
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KB9YNB
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« Reply #38 on: May 02, 2013, 06:27:28 PM »

...For instance, my house has a "disconnect" immediately next to the meter base, because my house breaker box is more centrally-located in the house.   The ground/neutral are required to be bonded at the very first disconnect after the meter, which is not *always* in the breaker box.

As does mine.  I believe that you've hit on it with your statement--
Quote
It may depend on the age of your house and which NEC was in effect when it was built.

One other thing,  I have never come across a feeder cable (meter to breaker box) that has both a neutral AND a ground cable in it.  They are both the same.  Also, I've never seen a breaker box that has both the ground bus and the neutral bus NOT connected directly to the metal of the box.  In any event, it's a moot point, since this is a ham radio site, not an electricians wiring site! 

It's not a moot point, because you have told people that their breaker box MUST have the neutral bonded to the ground.    This should ONLY be true if your breaker box is the MAIN disconnect.  Not ALL breaker boxes (even if it's the only one in your house) also serve as the MAIN disconnect.

You should NEVER see a service entrance cable from the Meter to the MAIN with a ground wire.     
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W6EM
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« Reply #39 on: May 03, 2013, 06:22:13 PM »

EM:  It has been my observation that on occasion an overheated conductor takes on a crystallized appearance and becomes brittle.

Overheating will anneal and soften conductors; or if hot enough, (1083C) overloading will melt or "fuse" copper.  Heat never crystalizes.  You may have observed surface pitting from acid gas corrosion from cooked PVC insulation nearby.

Quote
  Natural vibration caused by anything from machinery running or the house expanding and contracting to the wire vibrating in the walls can cause this fragile looking wire end to simply break.

I'll buy off on machinery work hardening solid conductors, but not structural thermal/moisture expansion or contraction.  More likely, if a receptacle or switch was not sufficiently tightened to the junction box, and it were to move back and forth enough, that might cause something to fail.  Best to use higher strand class stranded copper for things like motor leads.

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K1CJS
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« Reply #40 on: May 04, 2013, 08:42:45 AM »

...Apparently, you have never seen a sub panel downstream from a main panel.  When you purchase a breaker panel, the neutral bus is insulated for a reason.  Just that.  In case it is destined for use as a sub panel.  Usually, the manufacturers include a "grounding screw" which can be used to ground the bus to the metal can if it is going to be used as a main panel.

I have, but we weren't talking about a sub panel, nor were we speaking of how the panels come from the manufacturer, were we?  You can always throw 'buts' or 'how abouts' into a discussion--way after the point of the discussion.  After all, the discussion was about the wire connections between the meter socket and the breaker panel is done, not sub panels, nor how new breaker panels from the manufacturer come!  All you're doing is muddying waters for those who really don't understand.  Do you know what 'nitpicking' means?
« Last Edit: May 04, 2013, 08:48:17 AM by K1CJS » Logged
KA5IWO
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Posts: 131




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« Reply #41 on: May 04, 2013, 11:02:46 AM »

If you are comfortable with working on your on AC power mains and know the obvious dangers, you can probably fix this yourself.
Pull the meter base out, even if you have to cut the power companies tamper seal. If they ask, tell them an electrician did it. Never had a problem in my area with this but you may want to check. Check the lugs on the DEAD side of it first to make sure they are tight. Do NOT TOUCH the incoming wires to the meter from the power grid AS IT IS STILL HOT. Then proceed to your breaker box, find the incoming power wires to it from the meter base, check all connections in it starting with incoming power lugs first. If need be, pull and reseat all the breakers. Make sure all your hot wires, neutrals and grounds are good and tight and verify your outside ground connection is good.
PLEASE call an experienced electrician to do this for you if you do not feel safe doing this.
Most of all be safe.
Kevin / KA5IWO
 
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