I have a home workshop and needed 220 V circuits for certain power tools
and 120 V circuits for lighting and receptacles.
Around the same time our central air conditioning system faded and
died. We live in southern California and do not have many really hot
days, so we decided to not repair it again and just let it be.
The 220V 50A circuit for the AC happened to terminate on one wall of the
shop. So, taking advantage of the situation, I decided to set up a
subpanel using the former AC circuit. I am not an electrician, but have
done other electrical work around the house, including wiring attic
fans, adding new outdoor circuits, etc.
I added the subpanel and ran a 220/20A line (10-2G NM-B cable) to the
tablesaw and bandsaw and two 120/20 A lines (12-2G NM-B cable) for new
receptacles. The saws are each rated at 220V/13A and are never run
concurrently, One of the 120V receptacles was dedicated to a dust
collector rated at 120V/18A or 220V 9A.
I have been running this setup for about two years with no apparent
problems. I recently removed the cover on the subpanel to check
something and found that the neutral wire for the line feeding the dust
collector, and connected to the neutral bar was charred for about two
inches from the bus. Most of the insulation had been burned off along
those two inches. Also, the black plastic around the neutral bus shows
signs of having melted around the perimeter of the neutral bus bar.
The circuit breaker on the dust collector line was still engaged. I
also tested the cb and found that it does shut off power to the circuit.
I checked the screw which held the charred wire to the neutral bus bar
and it was tight I also checked the screw holding the neutral wire for
the other 120V line, and it was also tight.
The 50A line from the main box to the workshop subpanel is Aluminum
(house is mid 70's vintage) and the Murray subpanel is rated for both Al
and Cu wire.
Does anyone have any ideas as to what the problem could be?
Thanks,
CW
It was somewhere outside Barstow when "Todd Fatheree"
<[email protected]> wrote:
>"Andy Dingley" <[email protected]> wrote in message
>news:[email protected]...
>> It was somewhere outside Barstow when "Todd Fatheree"
>> <[email protected]> wrote:
>>
>> >Sorry, being a "bad conductor" and having "poor conductivity" are the
>same.
>>
>> Don't you think that someone who makes a distinction sufficient to use
>> each word appropriately in the same sentence is using it to make a
>> point ?
>
>One would hope, assuming they were using them correctly, which you're not.
>
>> A "conductor" and "conductivity" are not the same thing at all. One is
>> a bulk property of the material, one is a property of a specific
>> example of aluminium. Although aluminium's conductivity on paper is
>> good, make actual real-world wires from it and it's quite another
>> story -- you need to start worrying about those terminations.
>
>OK, if aluminum is a "bad conductor" in general, why do utilities use it
>almost exclusively for transmission and distribution of electricity? You're
>better off saying that aluminum is a "bad choice for household wiring",
>which is accurate, than getting too general by saying it's a "bad
>conductor".
>
>todd
>
--
Smert' spamionam
>
> I disagree. I think his statement was exactly correct.
>
> It's as if someone asked why we don't use balsa for plane bodies. A
> perfectly acceptable answer might be, "it's a bad wood," the
> implication being that it's an unsuitable wood for plane bodies.
>
> Someone making that statement isn't saying that balsa is bad as a wood
> ("aluminum is a bad conductor of electricity"), they are saying it's a
> bad wood for a plane body ("aluminum is a bad choice as a conductor in
> home wiring').
>
> There's no definition twisting involved. It's semantics. A play on
> words, and I thought a good one.
>
He is using "bad" to mean "inferior" rather than "poor". As such, he is
correct; aluminum is inferior to copper.
However, in standard English, a "bad conductor" means "poor conductivity"
and aluminum has excellent conductivity, so he is incorrect.
It is not semantics, it is poor English.
On Sun, 6 Mar 2005 10:09:40 -0600, "Todd Fatheree" <[email protected]>
wrote:
>"Andy Dingley" <[email protected]> wrote in message
>news:[email protected]...
>> It was somewhere outside Barstow when "Todd Fatheree"
>> <[email protected]> wrote:
>>
>> >The instructor replied "because aluminum is a bad conductor of
>electricity".
>>
>> Aluminium wire is a bad conductor (true). This is a different
>> statement from "aluminium has poor conductivity" (false). It's not
>> that aluminium itself is bad, it's the effects of aluminium as
>> acomponent in an overall system.
>
>Sorry, being a "bad conductor" and having "poor conductivity" are the same.
>My dictionary defines a conductor as "A substance or medium that conducts
>heat, light, sound, or especially an electric charge". Aluminum conducts
>electricity just fine. In fact, cost aside, one of the reasons it's used
>for overhead transmission and distribution is that it's a superior conductor
>to copper on a per-weight basis. You can certainly make the argument that
>aluminum (or aluminium) isn't suitable for certain applications, but don't
>twist definitions just to make a contrary point.
I disagree. I think his statement was exactly correct.
It's as if someone asked why we don't use balsa for plane bodies. A
perfectly acceptable answer might be, "it's a bad wood," the
implication being that it's an unsuitable wood for plane bodies.
Someone making that statement isn't saying that balsa is bad as a wood
("aluminum is a bad conductor of electricity"), they are saying it's a
bad wood for a plane body ("aluminum is a bad choice as a conductor in
home wiring').
There's no definition twisting involved. It's semantics. A play on
words, and I thought a good one.
- -
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
Lew Hodgett wrote:
> <[email protected]> writes:
>
> >The 50A line from the main box to the workshop subpanel is Aluminum
> >(house is mid 70's vintage) and the Murray subpanel is rated for
both Al
> >and Cu wire.
>
> Consider yourself lucky you still have a place to sleep.
>
> Get rid of that aluminum crap before the whole damn house burns down.
>
> Also replace the sub panel as well as the branch c'bkrs.
>
> Trust me, you are sitting on a potential powder keg.
>
> Lew
This isn't true Lew. Go down in your breaker panel and look at what
comes into it - aluminum. Look at what feeds your sub panel if you
have one - aluminum. It's the combination of aluminum and copper in
pigtails that caused problems in the 60's, not aluminum wire feeding
panels. The OP posted a problem with a branch circuit that was copper.
The aluminum feed lines coming into his sub panel hae nothing to do
with the copper branch circuits.
-Mike-
[email protected]
Lew wrote...
Totally different world.
Utilities commonly use Al conductors as service entrance feeders as
well
as distribution cables; however, that is a totally different
application
which the utilities address by using specific terminations crimped with
tools designed specifically for Al cable.
Take a look at the terminations made by the utility at the weather head
of a typical service entrance. (You don't find those terminations at
Home Depot)
Attempting to use Al conductor in a clamp type termination found on a
typical plug-in c'bkr of a residential load center or the same clamp
type termination found on the neutral and ground bus bars for branch
circuits is a totally different world.
Cold flow and ultimately melt down are just a matter of time.
Lew
So then I said...
Not really different Lew. The meter channel uses crimped lugs like
you're talking about, but your service panel uses aluminum feeders that
just clamp down in the main and on the buss bar the same way that your
copper branch circuits do. The same way that I believe the OP is
describing his sub panel to be.
The point the OP made - at least as far as I recall, is that his branch
circuites are copper. It's only his feed that is aluminum. That would
be essentially what you see in your primary panel. The buss bar is
aluminum, so he would not have any problems clamping an aluminum feeder
down. It's when you put copper in there that you contend with issues
of dissimilar metals and have to use products like no-ox to prevent
them.
-Mike-
"Seawulf" <[email protected]> wrote in message
news:WmKXd.22073$FM3.17025@fed1read02...
> Mike,
> Yes, the subpanel is set up as you describe with Al Feeder and, all
> copper to the subpanel circuits.
>
> You also say the buss bar is Al. My material recognition is not up to
> par, so, I really cannot tell. It certainly looks like it could be Al.
> The grounding bar appears to be the same material as do the hot
> terminals. The set screws in the neutral and ground buss appear to be
> the same material, but the set screws in the hot terminals have a color
> that looks about half way between Al and Brass. BTW, the bracket that
> connects the grounding buss to the case is the same material as the set
> screws on the hot terminals.
>
> So, what is it about the construction of this subpanel that allows it to
> be rated for AL or Cu wire, the Al bus terminals?
>
> Charlie
>
Well Charlie, I'm no metallurgist so I take the easy way out - I rely on the
label in the box. I'm guessing it's the clamping that allows for either
wire. It's when copper and aluminum are twisted together that the joint
will fail over time (heat). Most panels are rated for AL or Cu. There's
nothing special about yours. It's just the way most are made.
--
-Mike-
[email protected]
In article <h62Xd.5$FM3.4@fed1read02>, Seawulf <[email protected]> wrote:
>Doug Miller wrote:
>>
>> To carry 50A in aluminum, you need either (a) 4ga wire of any conductor
>> temperature rating, or (b) 6ga wire with a conductor temperature of at least
>> 75 deg C. 8ga aluminum is NOT Code-approved, nor is it safe, for carrying 50A
>> regardless of the conductor temperature.
>>
>Unfortunately, I just cannot make out more of the info on the sheathing
>than the 6 or 8 gauge point. So, I just do not know the temp rating.
In that case, it would be prudent to remove it, and replace it with 6/3 copper
with ground - the point being that, given that the wire is aluminum, if it's
8ga it's unsafe, period, and if it's 6ga you're unable to determine whether
it's safe or not. OTOH, 6ga copper is safe for 50A regardless of conductor
temperature.
--
Regards,
Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?
I want to thank all of you who responded. I even enjoyed the playful
wrestling with characteristics of Al wiring.
Having thought about this for a few days, now - before reading all of
your stimulating comments - I had begun to conclude that the charring of
the insulation on the neutral wire for the dust collector circuit was
perhaps,not the cause, but the result of the underlying problem. The
clue to the problem, I began to think was the melted plastic around the
neutral bus bar and the problem was the connection of the 50A feed
Neutral to the subpanel Neutral bus bar.
So, after reading your comments, especially Charley's - I believe that
to be the case. I think that the faulty connection heated the bus and
the dust collector wire had its insulation touching the bar, which would
explain why it was so charred and the feed and other circuit neutrals'
insulation was not affected.
I also take onboard the comments about the potential danger of Al wire.
Thanks for your help
Charley wrote:
> The quality of the termination of the wires that burned was poor , a result
> of an untight connection, corrosion of the conductor, or the inside of the
> terminal, etc. Since this poor connection added a resistance to the circuit,
> it caused heat to build up at that point. The circuit breaker didn't trip
> because you weren't pulling more current through it than it was rated for.
> Whenever you re-use old wiring or panels all of the terminations need to be
> cleaned thoroughly before they are assembled. In the case of aluminum wire
> this is even more important. It's also necessary to coat the aluminum
> conductor terminations with a special grease type compound that has been
> developed to prevent oxygen in the air from oxidizing the aluminum when it
> warms up from carrying heavy currents. This has to be done when you do the
> installation. Now it will be necessary to dis-assemble the problem
> connections, cut back the wires far enough to find undamaged insulation and
> conductors. Replace any terminal that shows any damage, and then clean and
> re-assemble all of the connections again applying the special grease to the
> aluminum connections. Make sure that you have every connection good and
> tight before you re-apply power and it should all be OK again. It's a good
> idea to inspect the panel connections every so often to try to catch this
> type of problem before it gets this bad. It's a good thing that you caught
> it when you did. It wasn't your wiring, but the poor electrical connection
> that caused the heat to build up and damage the wiring.
>
toller wrote:
> Interesting... on alt.home.repair no one even mentioned the aluminum wire.
<snip>
OK, you want the techie explanation, here goes:
1) Aluminum wire oxides in the atmosphere.
2) The oxidization increases the resistance of an electrical connection.
3) The increased resistance generates heat which causes "cold flow" of
the aluminum, thus reducing termination pressure, which also increases
the electrical resitance of the connection.
It is a never ending vicious cycle resulting in the melting of the
aluminum wire about 2"-3" up inside the insulation on the wire and often
a fire results.
The above is why aluminum conductor has not been used in buildings for
years.
Proper use of antioxidant compounds such as Alnox and larger conductors,
above 2/0 minimum, allow use of aluminum in many high current
applications, but definitely not branch circuits in housing applications.
HTH
Lew
"Andy Dingley" <[email protected]> wrote in message
news:[email protected]...
> It was somewhere outside Barstow when "Todd Fatheree"
> <[email protected]> wrote:
>
> >The instructor replied "because aluminum is a bad conductor of
electricity".
>
> Aluminium wire is a bad conductor (true). This is a different
> statement from "aluminium has poor conductivity" (false). It's not
> that aluminium itself is bad, it's the effects of aluminium as
> acomponent in an overall system.
>
> I'm just grateful post-war Britatin invented the superb ring system,
> rather than going with aluminium.
Sorry, being a "bad conductor" and having "poor conductivity" are the same.
My dictionary defines a conductor as "A substance or medium that conducts
heat, light, sound, or especially an electric charge". Aluminum conducts
electricity just fine. In fact, cost aside, one of the reasons it's used
for overhead transmission and distribution is that it's a superior conductor
to copper on a per-weight basis. You can certainly make the argument that
aluminum (or aluminium) isn't suitable for certain applications, but don't
twist definitions just to make a contrary point.
todd
In article <[email protected]>, Lew Hodgett <[email protected]> wrote:
>Attempting to use Al conductor in a clamp type termination found on a
>typical plug-in c'bkr of a residential load center or the same clamp
>type termination found on the neutral and ground bus bars for branch
>circuits is a totally different world.
True, but only in the sense that *much* more care is required in installation.
>
>Cold flow and ultimately melt down are just a matter of time.
Nonsense. Cold flow occurs when a connection is over-tightened. A connection
that is not overtorqued will not cold flow. Aluminum conductors, in terminals
designed for use with same, are safe enough when tightened to the proper
torque specification and no further, and of course when an appropriate
anti-oxidant is used.
_Properly_installed_ aluminum wiring is safe. Trouble is, it's a _whole_lot_
more difficult to install aluminum properly, as compared to copper. For
starters,
- use only devices, terminals, and connectors rated for use with aluminum
- use anti-oxidant paste everywhere
- use a torque wrench on *every* termination to avoid overtightening (that
includes the screws on receptacles and switches)
With copper, you don't have to worry about any of that: copper doesn't
cold-flow, any listed device is OK to use with copper, and copper oxide is
nearly as good a conductor of electricity as copper itself (aluminum oxide,
OTOH, makes a reasonably decent electrical *insulator*).
--
Regards,
Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?
<[email protected]> writes:
>The 50A line from the main box to the workshop subpanel is Aluminum
>(house is mid 70's vintage) and the Murray subpanel is rated for both Al
>and Cu wire.
Consider yourself lucky you still have a place to sleep.
Get rid of that aluminum crap before the whole damn house burns down.
Also replace the sub panel as well as the branch c'bkrs.
Trust me, you are sitting on a potential powder keg.
Lew
The rating info on the sheathing of the feed cable is very difficult to
read over the section of the cable that is exposed to view. But, it
appears to be either 8 or 6 gauge. Given that 8 gauge is rated, I
believe for only 40 Amps and this is off of a 50A breaker on the main
panel, I must assume it to be 6 gauge.
Also, all of the houses in our little development have the same central
air conditioning units, so I assume the feed line is original to the
house and was accepted as code-compliant in the mid 70's timeframe.
Thanks for your info,
CDW
toller wrote:
> "Lew Hodgett" <[email protected]> wrote in message
> news:[email protected]...
>
>><[email protected]> writes:
>>
>>
>>>The 50A line from the main box to the workshop subpanel is Aluminum
>>>(house is mid 70's vintage) and the Murray subpanel is rated for both Al
>>>and Cu wire.
>>
>>Consider yourself lucky you still have a place to sleep.
>>
>>Get rid of that aluminum crap before the whole damn house burns down.
>>
>
> Interesting... on alt.home.repair no one even mentioned the aluminum wire.
> Since it was not near the burnt area, it couldn't have been relevant. They
> said it had to be a bad connection, even it is seems okay. I would have to
> agree, as there really can't be another reason.
>
> Heavy gauge aluminum wire (#4 for 50a) is perfectly safe as long as
> everything is rated for aluminum; though it is prudent to check the
> tightness of connections now and then, and to use antioxidant paste. It is
> #12 and #14 that is dangerous.
>
>
"Lew Hodgett" <[email protected]> wrote in message
news:[email protected]...
> <[email protected]> writes:
>
>>The 50A line from the main box to the workshop subpanel is Aluminum
>>(house is mid 70's vintage) and the Murray subpanel is rated for both Al
>>and Cu wire.
>
> Consider yourself lucky you still have a place to sleep.
>
> Get rid of that aluminum crap before the whole damn house burns down.
>
Interesting... on alt.home.repair no one even mentioned the aluminum wire.
Since it was not near the burnt area, it couldn't have been relevant. They
said it had to be a bad connection, even it is seems okay. I would have to
agree, as there really can't be another reason.
Heavy gauge aluminum wire (#4 for 50a) is perfectly safe as long as
everything is rated for aluminum; though it is prudent to check the
tightness of connections now and then, and to use antioxidant paste. It is
#12 and #14 that is dangerous.
"Andy Dingley" <[email protected]> wrote in message
news:[email protected]...
> It was somewhere outside Barstow when "Todd Fatheree"
> <[email protected]> wrote:
>
> >Sorry, being a "bad conductor" and having "poor conductivity" are the
same.
>
> Don't you think that someone who makes a distinction sufficient to use
> each word appropriately in the same sentence is using it to make a
> point ?
One would hope, assuming they were using them correctly, which you're not.
> A "conductor" and "conductivity" are not the same thing at all. One is
> a bulk property of the material, one is a property of a specific
> example of aluminium. Although aluminium's conductivity on paper is
> good, make actual real-world wires from it and it's quite another
> story -- you need to start worrying about those terminations.
OK, if aluminum is a "bad conductor" in general, why do utilities use it
almost exclusively for transmission and distribution of electricity? You're
better off saying that aluminum is a "bad choice for household wiring",
which is accurate, than getting too general by saying it's a "bad
conductor".
todd
Yeah. Aluminium wire.
I had the same thing happen to me 30 years ago in a condo unit that was =
only 3 months old.
The flash was in an outlet box that was not being used. All the joints =
were tight but the wire still burned back about 6 inches.
Since then I have only used copper wire.
If you join aluminium and copper you will get a galvanic reaction that =
could result in a burn.
--=20
PDQ
--
=20
"Seawulf" <[email protected]> wrote in message =
news:97qWd.84759$JZ2.36934@fed1read02...
| I have a home workshop and needed 220 V circuits for certain power =
tools=20
| and 120 V circuits for lighting and receptacles.
|=20
| Around the same time our central air conditioning system faded and=20
| died. We live in southern California and do not have many really hot=20
| days, so we decided to not repair it again and just let it be.
|=20
| The 220V 50A circuit for the AC happened to terminate on one wall of =
the=20
| shop. So, taking advantage of the situation, I decided to set up a=20
| subpanel using the former AC circuit. I am not an electrician, but =
have=20
| done other electrical work around the house, including wiring attic=20
| fans, adding new outdoor circuits, etc.
|=20
| I added the subpanel and ran a 220/20A line (10-2G NM-B cable) to the=20
| tablesaw and bandsaw and two 120/20 A lines (12-2G NM-B cable) for new =
| receptacles. The saws are each rated at 220V/13A and are never run=20
| concurrently, One of the 120V receptacles was dedicated to a dust=20
| collector rated at 120V/18A or 220V 9A.
|=20
| I have been running this setup for about two years with no apparent=20
| problems. I recently removed the cover on the subpanel to check=20
| something and found that the neutral wire for the line feeding the =
dust=20
| collector, and connected to the neutral bar was charred for about two=20
| inches from the bus. Most of the insulation had been burned off along =
| those two inches. Also, the black plastic around the neutral bus shows =
| signs of having melted around the perimeter of the neutral bus bar.
|=20
| The circuit breaker on the dust collector line was still engaged. I=20
| also tested the cb and found that it does shut off power to the =
circuit.
|=20
| I checked the screw which held the charred wire to the neutral bus bar =
| and it was tight I also checked the screw holding the neutral wire =
for=20
| the other 120V line, and it was also tight.
|=20
| The 50A line from the main box to the workshop subpanel is Aluminum=20
| (house is mid 70's vintage) and the Murray subpanel is rated for both =
Al=20
| and Cu wire.
|=20
| Does anyone have any ideas as to what the problem could be?
|=20
| Thanks,
| CW
"Andy Dingley" <[email protected]> wrote in message
news:[email protected]...
> It was somewhere outside Barstow when "Todd Fatheree"
> <[email protected]> wrote:
>
> >OK, if aluminum is a "bad conductor" in general, why do utilities use it
> >almost exclusively for transmission and distribution of electricity?
>
> Because at that scale, they're using far more material with relatively
> fewer joints. The benefits increase, the costs are more manageable.
> Their circuits are also powered almost continuously and a flowing
> current avoids many of aluminium's problems. It's circuits that are
> cycled for long off periods that are most prone to the typical faults.
So what you're saying, without coming out and saying it, is that aluminum is
a "good conductor" for the utilities?
> You'll notice that telephone companies, another great user of copper
> wire, never went for aluminium.
I've never said that aluminum was appropriate for all uses. I just
disagreed with the blanket statement that aluminum is a "bad conductor".
You'll also notice that the telcos are increasingly moving to fiber. Just
gotta get that "last mile". ;-)
todd
Mike Marlow wrote:
> Lew wrote...
>
> Totally different world.
>
> Utilities commonly use Al conductors as service entrance feeders as
> well
> as distribution cables; however, that is a totally different
> application
> which the utilities address by using specific terminations crimped with
>
> tools designed specifically for Al cable.
Mike,
Yes, the subpanel is set up as you describe with Al Feeder and, all
copper to the subpanel circuits.
You also say the buss bar is Al. My material recognition is not up to
par, so, I really cannot tell. It certainly looks like it could be Al.
The grounding bar appears to be the same material as do the hot
terminals. The set screws in the neutral and ground buss appear to be
the same material, but the set screws in the hot terminals have a color
that looks about half way between Al and Brass. BTW, the bracket that
connects the grounding buss to the case is the same material as the set
screws on the hot terminals.
So, what is it about the construction of this subpanel that allows it to
be rated for AL or Cu wire, the Al bus terminals?
Charlie
>
> Take a look at the terminations made by the utility at the weather head
>
> of a typical service entrance. (You don't find those terminations at
> Home Depot)
>
>
> Attempting to use Al conductor in a clamp type termination found on a
> typical plug-in c'bkr of a residential load center or the same clamp
> type termination found on the neutral and ground bus bars for branch
> circuits is a totally different world.
>
> Not really different Lew. The meter channel uses crimped lugs like
> you're talking about, but your service panel uses aluminum feeders that
> just clamp down in the main and on the buss bar the same way that your
> copper branch circuits do. The same way that I believe the OP is
> describing his sub panel to be.
>
> The point the OP made - at least as far as I recall, is that his branch
> circuites are copper. It's only his feed that is aluminum. That would
> be essentially what you see in your primary panel. The buss bar is
> aluminum, so he would not have any problems clamping an aluminum feeder
> down. It's when you put copper in there that you contend with issues
> of dissimilar metals and have to use products like no-ox to prevent
> them.
>
> -Mike-
>
On Sun, 06 Mar 2005 17:42:20 GMT, "toller" <[email protected]> wrote:
>>
>> I disagree. I think his statement was exactly correct.
>>
>> It's as if someone asked why we don't use balsa for plane bodies. A
>> perfectly acceptable answer might be, "it's a bad wood," the
>> implication being that it's an unsuitable wood for plane bodies.
>>
>> Someone making that statement isn't saying that balsa is bad as a wood
>> ("aluminum is a bad conductor of electricity"), they are saying it's a
>> bad wood for a plane body ("aluminum is a bad choice as a conductor in
>> home wiring').
>>
>> There's no definition twisting involved. It's semantics. A play on
>> words, and I thought a good one.
>>
>He is using "bad" to mean "inferior" rather than "poor". As such, he is
>correct; aluminum is inferior to copper.
>However, in standard English, a "bad conductor" means "poor conductivity"
>and aluminum has excellent conductivity, so he is incorrect.
>It is not semantics, it is poor English.
Given that the OP (at least on this segment), Andy Dingely, is from
the Auld Sod and speaking the King's English, instead of this
bastardized colonial treacle with which we wrestle daily on this side
of the pond, I'll defer to his use.
- -
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
In article <DXIWd.113651$JZ2.12033@fed1read02>, Seawulf <[email protected]> wrote:
>The rating info on the sheathing of the feed cable is very difficult to
>read over the section of the cable that is exposed to view. But, it
>appears to be either 8 or 6 gauge. Given that 8 gauge is rated, I
>believe for only 40 Amps and this is off of a 50A breaker on the main
>panel, I must assume it to be 6 gauge.
You simply CAN'T assume that. You have NO assurance that the person who
installed that matched the breaker to the conductors correctly, and, from what
you've posted so far, it sounds to me like he did NOT.
Furthermore, you said in your original post that your feed wire is aluminum.
8ga COPPER is rated 40A; aluminum conductors have lower ratings than copper
conductors of the same gauge.
The current rating (ampacity) depends on the material, the wire gauge, and the
temperature rating of the insulation.
To carry 50A in aluminum, you need either (a) 4ga wire of any conductor
temperature rating, or (b) 6ga wire with a conductor temperature of at least
75 deg C. 8ga aluminum is NOT Code-approved, nor is it safe, for carrying 50A
regardless of the conductor temperature.
>Also, all of the houses in our little development have the same central
>air conditioning units, so I assume the feed line is original to the
>house and was accepted as code-compliant in the mid 70's timeframe.
You can't assume that either.
--
Regards,
Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?
"Andy Dingley" wrote in message
> example of aluminium. Although aluminium's conductivity on paper is
> good, make actual real-world wires from it and it's quite another
> story -- you need to start worrying about those terminations.
"Bad" for home wiring because of termination issues, but good enough for
transmission lines.
--
www.e-woodshop.net
Last update: 11/06/04
The quality of the termination of the wires that burned was poor , a result
of an untight connection, corrosion of the conductor, or the inside of the
terminal, etc. Since this poor connection added a resistance to the circuit,
it caused heat to build up at that point. The circuit breaker didn't trip
because you weren't pulling more current through it than it was rated for.
Whenever you re-use old wiring or panels all of the terminations need to be
cleaned thoroughly before they are assembled. In the case of aluminum wire
this is even more important. It's also necessary to coat the aluminum
conductor terminations with a special grease type compound that has been
developed to prevent oxygen in the air from oxidizing the aluminum when it
warms up from carrying heavy currents. This has to be done when you do the
installation. Now it will be necessary to dis-assemble the problem
connections, cut back the wires far enough to find undamaged insulation and
conductors. Replace any terminal that shows any damage, and then clean and
re-assemble all of the connections again applying the special grease to the
aluminum connections. Make sure that you have every connection good and
tight before you re-apply power and it should all be OK again. It's a good
idea to inspect the panel connections every so often to try to catch this
type of problem before it gets this bad. It's a good thing that you caught
it when you did. It wasn't your wiring, but the poor electrical connection
that caused the heat to build up and damage the wiring.
--
Charley
"Seawulf" <[email protected]> wrote in message
news:97qWd.84759$JZ2.36934@fed1read02...
> I have a home workshop and needed 220 V circuits for certain power tools
> and 120 V circuits for lighting and receptacles.
>
> Around the same time our central air conditioning system faded and
> died. We live in southern California and do not have many really hot
> days, so we decided to not repair it again and just let it be.
>
> The 220V 50A circuit for the AC happened to terminate on one wall of the
> shop. So, taking advantage of the situation, I decided to set up a
> subpanel using the former AC circuit. I am not an electrician, but have
> done other electrical work around the house, including wiring attic
> fans, adding new outdoor circuits, etc.
>
> I added the subpanel and ran a 220/20A line (10-2G NM-B cable) to the
> tablesaw and bandsaw and two 120/20 A lines (12-2G NM-B cable) for new
> receptacles. The saws are each rated at 220V/13A and are never run
> concurrently, One of the 120V receptacles was dedicated to a dust
> collector rated at 120V/18A or 220V 9A.
>
> I have been running this setup for about two years with no apparent
> problems. I recently removed the cover on the subpanel to check
> something and found that the neutral wire for the line feeding the dust
> collector, and connected to the neutral bar was charred for about two
> inches from the bus. Most of the insulation had been burned off along
> those two inches. Also, the black plastic around the neutral bus shows
> signs of having melted around the perimeter of the neutral bus bar.
>
> The circuit breaker on the dust collector line was still engaged. I
> also tested the cb and found that it does shut off power to the circuit.
>
> I checked the screw which held the charred wire to the neutral bus bar
> and it was tight I also checked the screw holding the neutral wire for
> the other 120V line, and it was also tight.
>
> The 50A line from the main box to the workshop subpanel is Aluminum
> (house is mid 70's vintage) and the Murray subpanel is rated for both Al
> and Cu wire.
>
> Does anyone have any ideas as to what the problem could be?
>
> Thanks,
> CW
On Sun, 06 Mar 2005 12:18:10 +0000, Andy Dingley
<[email protected]> wrote:
>It was somewhere outside Barstow when "Todd Fatheree"
><[email protected]> wrote:
>
>>The instructor replied "because aluminum is a bad conductor of electricity".
>
>Aluminium wire is a bad conductor (true). This is a different
>statement from "aluminium has poor conductivity" (false). It's not
>that aluminium itself is bad, it's the effects of aluminium as
>acomponent in an overall system.
>
>I'm just grateful post-war Britatin invented the superb ring system,
>rather than going with aluminium.
OK, I'll bite.
What is the "superb ring system" ?
Rad
You're very welcome (I say for the others), and from the volume and intensity
of the replies, you now know why this is rec.electrical.woodworking. Other
than, possibly, staining cherry, few posts get as many quick responses as
electrical issues, and this has been the case here for many years.
Interestingly though, IMO the quality of the responses is much better than
several years ago; one might almost assume some of you guys know what you're
talking about:-)
GerryG
An EE who has nothing more to add, since several already said it all.
On Sun, 06 Mar 2005 11:38:59 -0800, Seawulf <[email protected]> wrote:
>I want to thank all of you who responded. I even enjoyed the playful
>wrestling with characteristics of Al wiring.
>
>Having thought about this for a few days, now - before reading all of
>your stimulating comments - I had begun to conclude that the charring of
>the insulation on the neutral wire for the dust collector circuit was
>perhaps,not the cause, but the result of the underlying problem. The
>clue to the problem, I began to think was the melted plastic around the
>neutral bus bar and the problem was the connection of the 50A feed
>Neutral to the subpanel Neutral bus bar.
>
>So, after reading your comments, especially Charley's - I believe that
>to be the case. I think that the faulty connection heated the bus and
>the dust collector wire had its insulation touching the bar, which would
>explain why it was so charred and the feed and other circuit neutrals'
>insulation was not affected.
>
>I also take onboard the comments about the potential danger of Al wire.
>
>
>Thanks for your help
Doug Miller wrote:
> In article <DXIWd.113651$JZ2.12033@fed1read02>, Seawulf <[email protected]> wrote:
>
>>The rating info on the sheathing of the feed cable is very difficult to
>>read over the section of the cable that is exposed to view. But, it
>>appears to be either 8 or 6 gauge. Given that 8 gauge is rated, I
>>believe for only 40 Amps and this is off of a 50A breaker on the main
>>panel, I must assume it to be 6 gauge.
>
>
> You simply CAN'T assume that. You have NO assurance that the person who
> installed that matched the breaker to the conductors correctly, and, from what
> you've posted so far, it sounds to me like he did NOT.
You're right, of course. I guess what I was trying to say was that,
trying to evaluate the possible causes of the problem, I look for the
most likely events and go from there. If that does not pan out, I
examine the less likely events.
You may be correct, there, also, in that the failure of the installer to
perform the job correctly coupled with the failure of the municipal
inspector to catch the error may be more likely than I expected. I
realise they are not necessarily independent probabilities; i.e. neither
of them were necessarily doing their job conscientiously.
Thanks for pointing this out!
>
> Furthermore, you said in your original post that your feed wire is aluminum.
> 8ga COPPER is rated 40A; aluminum conductors have lower ratings than copper
> conductors of the same gauge.
>
> The current rating (ampacity) depends on the material, the wire gauge, and the
> temperature rating of the insulation.
>
> To carry 50A in aluminum, you need either (a) 4ga wire of any conductor
> temperature rating, or (b) 6ga wire with a conductor temperature of at least
> 75 deg C. 8ga aluminum is NOT Code-approved, nor is it safe, for carrying 50A
> regardless of the conductor temperature.
>
Unfortunately, I just cannot make out more of the info on the sheathing
than the 6 or 8 gauge point. So, I just do not know the temp rating.
>
>>Also, all of the houses in our little development have the same central
>>air conditioning units, so I assume the feed line is original to the
>>house and was accepted as code-compliant in the mid 70's timeframe.
>
>
> You can't assume that either.
>
Point taken...thanks... CDW
> --
> Regards,
> Doug Miller (alphageek at milmac dot com)
>
> Nobody ever left footprints in the sands of time by sitting on his butt.
> And who wants to leave buttprints in the sands of time?
It was somewhere outside Barstow when "Todd Fatheree"
<[email protected]> wrote:
>OK, if aluminum is a "bad conductor" in general, why do utilities use it
>almost exclusively for transmission and distribution of electricity?
Because at that scale, they're using far more material with relatively
fewer joints. The benefits increase, the costs are more manageable.
Their circuits are also powered almost continuously and a flowing
current avoids many of aluminium's problems. It's circuits that are
cycled for long off periods that are most prone to the typical faults.
You'll notice that telephone companies, another great user of copper
wire, never went for aluminium.
"LRod" <[email protected]> wrote in message
news:[email protected]...
> On Sun, 6 Mar 2005 10:09:40 -0600, "Todd Fatheree" <[email protected]>
> wrote:
> >Sorry, being a "bad conductor" and having "poor conductivity" are the
same.
> >My dictionary defines a conductor as "A substance or medium that conducts
> >heat, light, sound, or especially an electric charge". Aluminum conducts
> >electricity just fine. In fact, cost aside, one of the reasons it's used
> >for overhead transmission and distribution is that it's a superior
conductor
> >to copper on a per-weight basis. You can certainly make the argument
that
> >aluminum (or aluminium) isn't suitable for certain applications, but
don't
> >twist definitions just to make a contrary point.
>
> I disagree. I think his statement was exactly correct.
Same question to you. Why do electric utilites use aluminum almost
exclusively for transmission and distribution if aluminum is a "bad
conductor".
> It's as if someone asked why we don't use balsa for plane bodies. A
> perfectly acceptable answer might be, "it's a bad wood," the
> implication being that it's an unsuitable wood for plane bodies.
Where this analogy fails is that unlike balsa wood and airplanes, aluminum
is widely used to conduct electricity.
> Someone making that statement isn't saying that balsa is bad as a wood
> ("aluminum is a bad conductor of electricity"), they are saying it's a
> bad wood for a plane body ("aluminum is a bad choice as a conductor in
> home wiring').
If you stuck with the last part, you'd be correct.
> There's no definition twisting involved. It's semantics. A play on
> words, and I thought a good one.
The problem is that the statement that aluminum is a bad conductor is the
opposite of semantics, because it's inaccurate. As you correctly said above
its "a bad choice as a conductor in home wiring".
todd
On Sat, 05 Mar 2005 14:10:28 -0800, the inscrutable Seawulf
<[email protected]> spake:
>something and found that the neutral wire for the line feeding the dust
>collector, and connected to the neutral bar was charred for about two
>inches from the bus. Most of the insulation had been burned off along
>those two inches. Also, the black plastic around the neutral bus shows
>signs of having melted around the perimeter of the neutral bus bar.
>
>The circuit breaker on the dust collector line was still engaged. I
>also tested the cb and found that it does shut off power to the circuit.
>
>I checked the screw which held the charred wire to the neutral bus bar
>and it was tight I also checked the screw holding the neutral wire for
>the other 120V line, and it was also tight.
First loosen, then tighten to make sure the screws aren't just frozen.
Also check your wire gauge vs. the current running through it.
>The 50A line from the main box to the workshop subpanel is Aluminum
>(house is mid 70's vintage) and the Murray subpanel is rated for both Al
>and Cu wire.
"DUMP THE ALUMINUM WIRE NOW, BEFORE YOU HAVE A REAL FIRE" he said
quietly and unemotionally while cursing the aluminum crapwire.
>Does anyone have any ideas as to what the problem could be?
Resistance in the connection causes wires to char like that.
==========================================================
Save the ||| http://diversify.com
Endangered SKEETS! ||| Web Application Programming
==========================================================
Hi Andy,
Just out of curiousity what is the "Superb ring system".
Pat
On Sun, 06 Mar 2005 12:18:10 +0000, Andy Dingley
<[email protected]> wrote:
>It was somewhere outside Barstow when "Todd Fatheree"
><[email protected]> wrote:
>
>>The instructor replied "because aluminum is a bad conductor of electricity".
>
>Aluminium wire is a bad conductor (true). This is a different
>statement from "aluminium has poor conductivity" (false). It's not
>that aluminium itself is bad, it's the effects of aluminium as
>acomponent in an overall system.
>
>I'm just grateful post-war Britatin invented the superb ring system,
>rather than going with aluminium.
It was somewhere outside Barstow when "Todd Fatheree"
<[email protected]> wrote:
>The instructor replied "because aluminum is a bad conductor of electricity".
Aluminium wire is a bad conductor (true). This is a different
statement from "aluminium has poor conductivity" (false). It's not
that aluminium itself is bad, it's the effects of aluminium as
acomponent in an overall system.
I'm just grateful post-war Britatin invented the superb ring system,
rather than going with aluminium.
"toller" <[email protected]> wrote in message
news:[email protected]...
>
> "Lew Hodgett" <[email protected]> wrote in message
> news:[email protected]...
> > <[email protected]> writes:
> >
> >>The 50A line from the main box to the workshop subpanel is Aluminum
> >>(house is mid 70's vintage) and the Murray subpanel is rated for both Al
> >>and Cu wire.
> >
> > Consider yourself lucky you still have a place to sleep.
> >
> > Get rid of that aluminum crap before the whole damn house burns down.
> >
> Interesting... on alt.home.repair no one even mentioned the aluminum wire.
> Since it was not near the burnt area, it couldn't have been relevant.
They
> said it had to be a bad connection, even it is seems okay. I would have
to
> agree, as there really can't be another reason.
>
> Heavy gauge aluminum wire (#4 for 50a) is perfectly safe as long as
> everything is rated for aluminum; though it is prudent to check the
> tightness of connections now and then, and to use antioxidant paste. It
is
> #12 and #14 that is dangerous.
Reminds me of a home repair class I took as a younger man on the mistaken
belief that I would learn something useful. During a discussion on the
dangers of aluminum household wiring, someone asked why aluminum was bad.
The instructor replied "because aluminum is a bad conductor of electricity".
Having spend 7 years designing insulators for transmission and distribution
power lines, I thought "well somebody had better inform the utility
engineers fast", seeing as probably 99% of all T & D lines are strung with
aluminum.
todd
It was somewhere outside Barstow when Eradicate Sampson
<[email protected]> wrote:
>What is the "superb ring system" ?
Post-war copper shortage, together with a housing shortage owing to
wartime bombing and rapid post-war breeding. Everyone wanted houses,
with electrics, and with reduced amounts of copper to wire them.
Some countries, including America, switched to aluminium wire.
Aluminium was cheap at the time, owing to huge numbers of scrap
aircraft. Britain OTOH, just invented the Land Rover as a way of
making exportable vehicles that used aluminium instead of steel.
The British solution to house wiring was the "ring" system. The
previous "radial" system, as still used in most countries, places a
small number of sockets onto separate circuits and fuses each circuit
in a central fusebox. Lots of wire, one to each circuit, lots of
fuses, and poor safety for over-current faults as the multiple sockets
require each circuit to have a relatively large fuse.
Thr ring system still uses copper, but it places all the sockets in a
large area (usually one floor of a house) onto one circuit and one
fusebox fuse. It uses a single loop of medium-heavy cable, which is a
very efficient way of using the scarce material - delivered power for
a given copper area is something like 4-6 times that of the US system,
depending on whether it's a small flat or larger house. Voltage drop
problems are avoided by using a loop, not a radial. The great
advantage of the system comes from its better use of "diversity" -
it's good to provide many socket outlets, but many of them are little
used, and rarely do they carry substantial loads. The radial system
has to wire everything up for the worst case, and do it individually.
The downside is a more complex plug on each appliance, requiring a
fuse. However this also allows fuses to be related to the real
appliance load, not the location. Most of my appliance are fused for
just 1A, but I can safely plug a 3kW welder or compressor into the
same socket, anywhere in the house.
If you look at the fire statistics for UK domestic fires, by far the
biggest problem comes from damage somewhere along a cable (chafing,
rodents, or perished rubber). Relatively speaking we get very little
trouble from connectors or panels.
I just had a home built and I noticed that the power company used aluminum
cable which they trenched underground from the pole to my house.
"Seawulf" <[email protected]> wrote in message
news:DXIWd.113651$JZ2.12033@fed1read02...
> The rating info on the sheathing of the feed cable is very difficult to
> read over the section of the cable that is exposed to view. But, it
> appears to be either 8 or 6 gauge. Given that 8 gauge is rated, I
> believe for only 40 Amps and this is off of a 50A breaker on the main
> panel, I must assume it to be 6 gauge.
>
> Also, all of the houses in our little development have the same central
> air conditioning units, so I assume the feed line is original to the
> house and was accepted as code-compliant in the mid 70's timeframe.
>
> Thanks for your info,
> CDW
>
>
> toller wrote:
> > "Lew Hodgett" <[email protected]> wrote in message
> > news:[email protected]...
> >
> >><[email protected]> writes:
> >>
> >>
> >>>The 50A line from the main box to the workshop subpanel is Aluminum
> >>>(house is mid 70's vintage) and the Murray subpanel is rated for both
Al
> >>>and Cu wire.
> >>
> >>Consider yourself lucky you still have a place to sleep.
> >>
> >>Get rid of that aluminum crap before the whole damn house burns down.
> >>
> >
> > Interesting... on alt.home.repair no one even mentioned the aluminum
wire.
> > Since it was not near the burnt area, it couldn't have been relevant.
They
> > said it had to be a bad connection, even it is seems okay. I would have
to
> > agree, as there really can't be another reason.
> >
> > Heavy gauge aluminum wire (#4 for 50a) is perfectly safe as long as
> > everything is rated for aluminum; though it is prudent to check the
> > tightness of connections now and then, and to use antioxidant paste. It
is
> > #12 and #14 that is dangerous.
> >
> >
It was somewhere outside Barstow when "Todd Fatheree"
<[email protected]> wrote:
>So what you're saying, without coming out and saying it, is that aluminum is
>a "good conductor" for the utilities?
No - I was talking about in-house wiring, not utilitites. You're the
one claiming that the OP's problems and near house fire couldn't have
been caused by the use of aluminium, because 440kV systems manage to
use it.
"Andy Dingley" <[email protected]> wrote in message
news:[email protected]...
> It was somewhere outside Barstow when "Todd Fatheree"
> <[email protected]> wrote:
>
> >So what you're saying, without coming out and saying it, is that aluminum
is
> >a "good conductor" for the utilities?
>
> No - I was talking about in-house wiring, not utilitites. You're the
> one claiming that the OP's problems and near house fire couldn't have
> been caused by the use of aluminium, because 440kV systems manage to
> use it.
Ah, yes...I was wondering how long it would take for the qualifications to
be made. I've been very clear all along the contexts I've been talking
about and have said more than once that aluminum is sub-optimal for home
wiring. But, hey, nice try at a misdirection after being painted into a
corner. Now that the tactic is just to start making up things I never said,
I'll just bow out.
todd
It was somewhere outside Barstow when "Todd Fatheree"
<[email protected]> wrote:
>Sorry, being a "bad conductor" and having "poor conductivity" are the same.
Don't you think that someone who makes a distinction sufficient to use
each word appropriately in the same sentence is using it to make a
point ?
A "conductor" and "conductivity" are not the same thing at all. One is
a bulk property of the material, one is a property of a specific
example of aluminium. Although aluminium's conductivity on paper is
good, make actual real-world wires from it and it's quite another
story -- you need to start worrying about those terminations.
Mike wrote:
>
> This isn't true Lew. Go down in your breaker panel and look at what
> comes into it - aluminum. Look at what feeds your sub panel if you
> have one - aluminum. It's the combination of aluminum and copper in
> pigtails that caused problems in the 60's, not aluminum wire feeding
> panels. The OP posted a problem with a branch circuit that was copper.
> The aluminum feed lines coming into his sub panel hae nothing to do
> with the copper branch circuits.
Totally different world.
Utilities commonly use Al conductors as service entrance feeders as well
as distribution cables; however, that is a totally different application
which the utilities address by using specific terminations crimped with
tools designed specifically for Al cable.
Take a look at the terminations made by the utility at the weather head
of a typical service entrance. (You don't find those terminations at
Home Depot)
Attempting to use Al conductor in a clamp type termination found on a
typical plug-in c'bkr of a residential load center or the same clamp
type termination found on the neutral and ground bus bars for branch
circuits is a totally different world.
Cold flow and ultimately melt down are just a matter of time.
Lew
"LRod" wrote in message
> Given that the OP (at least on this segment), Andy Dingely, is from
> the Auld Sod and speaking the King's English, instead of this
> bastardized colonial treacle with which we wrestle daily on this side
> of the pond, I'll defer to his use.
Wouldna that sair be a unco mistake, wot?
--
www.e-woodshop.net
Last update: 11/06/04