Info to backup safety of aluminum wiring?

[Harry Muscle]

What about connection devices that are designed for larger aluminum wiring ... but there happens to be a version of them that accepts smaller wires? There's a whole bunch of such connectors shown in this catalog:

. I'm assuming some of these would normally be found inside of a breaker panel to attach the aluminum wire comming in from outside. As well as used to make connections for larger aluminum wire that supplies ovens, etc. However, a lot of these connectors accept 14 awg wire too, therefore, would using such connectors be safer than using wirenuts. After all the safety of wirenuts is not agreed upon by all, but how about the safety of such connectors?

Thanks, Harry

[Matt Whiting]

How is the steel spring any different for Al wire than for Cu wire? It's heating is a function of the current through it or what it absorbs from the wire, not a function of the type of metal connected to it. Heat is generated by ohmic resistance, and that comes from corrosion between the Aluminum wires or the wires and the wire nut spring, not the spring itself.

Matt

[Duane Bozarth]

Bud wrote: ....

Perhaps, and wish it to be so...hope there isn't some legal-beagle sitting in the background somewhere collecting anecdotal data in preparation for a mass-mailing to enlist clients.

Maybe I'm just overly sensitive as I've a collection of some 10 or so such mailings over the last year or two and there are at least three local late night TV adds currently or recently fishing for medical/pharamceutical/product liability participants... :(

[Bud]

Steel has a high resistivity, which is why it is not used as a conductor. The tests show the wires do not contact each other because of oxide on the aluminum. The steel spring breaks through the oxide to make contact with the aluminum conductors. This means all the current is going through the spring. A CPSC report at

a 2 volt drop across the wire nut at 17 amps. This is only about

0.1 ohm resistance but is a 34 watt heater. At this current level the spring is red hot. This destroys the insulation on the wires and the wire nut and can start a fire. But the voltage drop is low and constant so lights are not dim and do not flicker. Later in the deterioration the the connection can totally fail, possibly with arcing that generates a lot more heat (more likely fire).

One wire nut that failed this way was the Ideal #65 twister which is listed for aluminum/copper. Cleverly the plastic shell and the antioxide paste in the wirenut are both combustible.

(The link above is part of a slide show that goes forward and back.)

links to this site and others of interest.

Bud--

[Bud]

Tests show that failure in wire nuts result from no contact between the wires because of oxide on the aluminum. The steel spring breaks through the oxide to make contact with the aluminum conductors. This means all the current is going through the spring. A CPSC report at

a 2 volt drop across the wire nut at 17 amps. This is only about

0.1 ohm resistance but is a 34 watt heater. At this current level the spring is red hot. This destroys the insulation on the wires and the wire nut and can start a fire. But the voltage drop is low and constant so lights are not dim and do not flicker. Since there is no arc, there is nothing for the AFCI to see.

Later in the deterioration the the connection can totally fail, possibly with arcing that generates a lot more heat. Arcing here would be picked up by an AFCI.

(The link above is part of a slide show that goes forward and back.)

links to this site and others of interest.

Bud--

[stevenal]

Note the split bolt connector is not UL aprroved for aluminum. I used the

[Harry Muscle]

Are split bolt connectors in general not UL approved for aluminum to copper connections? Or just the ones in the link I've provided?

Thanks, Harry

[Harry Muscle]

I just did a search on split bolt, aluminum, and UL, and it looks like you must have been refering to just the link that I provided above, since this page for example lists split bolt connectors designed for joining aluminum to copper and it says that they are UL and CSA certified:

. So I've just answered my own question as to what you were refering too ...

Thanks, Harry

P.S. Maybe I should start a new thread about this whole idea of using larger connectors with aluminum wire ... since this is totally off topic from where this thread started.

[Tekkie®]

SQLit posted for all of us... I don't top post - see either inline or at bottom.

tape build up stress cones?? What are they? Googled but no results...

[Doug B Taylor]

Tekkie -

An 'old fashion' method of terminating high voltage cabling.

Regards,

Doug

[Gerald Newton]

In northern Alaska where I am at, aluminum wire is rarely used. The extreme temperatures cause too many problems with cold flow.

But the AFCI problem you bring up is interesting because according to the Zlan site the inventor of the AFCI chip had to find a way to distinguish good arcs like a light switch turning on and off from a bad arc. I wonder if he analyzed all the possible combinations of aluminum to copper connections.

[petersonra]

the utility of afcis is somewhat dubious to begin with.

it is supposed to detect an arc, such as might happen when an extension cord is damaged.

whether they actually do or not is not clear.

in any case they will not detect the heating that occurs on an aluminum conenction that has started to oxidize.

[TokaMundo]

On 16 Aug 2005 14:20:41 -0700, [e-mail] Gave us:

It will if it gets "noisy" enough.

[Bob Peterson]

No it won't. AFCIs detect arcs, and at fairly high current levels. The oxidation that forms on aluminum connections reduces the current due to the resistance of the connection, thats what causes the heat, and the fires.

[Member TPVFD]

The manufacturers do not make it clear that AFCIs cannot detect series arcs, such as those resulting from an oxidizing connection, until they progress to a ground fault which draws at least thirty milliamperes. If the arcing connection does not cause a ground fault the AFCI cannot detect it and the heat it generates can kindle a fire. They can detect a parallel arc such as when a screw penetrates a cable and causes a high resistance arcing fault between the current carrying conductors. Such parallel arcs are not that common.

-- Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison

[Bud]

I keep forgetting that.

The 2005 NEC requires AFCIs with series AND parallel protection starting

1-1-2008. I don't know of any on the market now.

Bud--

[clifto]

GOOD conductor? Yes, if properly installed. Durable, etc.? Same answer. But silver and copper are better conductors of electricity.

[John Gilmer]

Sounds like the AFCI folks sold the NEC a bill of goods!

[Bud]

From

As part of the U.S. Consumer Product Safety Commission's (CPSC's) 1994 and 1995 efforts to reduce residential electrical system fires, the CPSC sponsored work on detecting and monitoring conditions that could lead to or cause fires in homes. The work was performed by Underwriters Laboratories Inc. (UL) and was documented in a report entitled, "Technology for Detecting and Monitoring Conditions that Could Cause Electrical Wiring System Fires." The study uncovered several possible technologies and concluded that arc-fault detection combined with ground-fault protection was the most promising technology to reduce the risk of fire when combined with conventional circuit breakers. At that time, such an arc-fault circuit breaker did not exist as a commercial device. Additional research has led to the development of the AFCI as a commercial product.

------------------- Series arcs, protection for which is being added to AFCIs, include loose connections. The current is limited by the load current downstream from the arc, so they won't trip breakers. They can, however, generate a lot of heat.

The NEC is a pretty pragmatic code. Changes usually require a demonstration that the change will improve safety.

Bud--