Aluminum/Copper Splice

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cruzader

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Hi All,

The elec contractor was installing an oven and down the road it caused a fire when the aluminum wire from the panel circuit was spliced inside the jbox with a copper wire from the oven. Is there a code section that prohibits this??
(The install was in 2012, so I assume the code used was 2008, but it was in CA so maybe it was 2008? I know CA is longer in accepting newer NEC code versions).

P.S.,
The install manual specifically says to use a 50A circuit and they used a 40A. I don't see how this could cause the wire to overheat since the breaker would, if anything, trip sooner.

Thank you in advance.
 
cruzader said:
Hi All,

The elec contractor was installing an oven and down the road it caused a fire when the aluminum wire from the panel circuit was spliced inside the jbox with a copper wire from the oven. Is there a code section that prohibits this??
(The install was in 2012, so I assume the code used was 2008, but it was in CA so maybe it was 2008? I know CA is longer in accepting newer NEC code versions).

P.S.,
The install manual specifically says to use a 50A circuit and they used a 40A. I don't see how this could cause the wire to overheat since the breaker would, if anything, trip sooner.

Thank you in advance.
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Well, if they used wire which can only safely handle 30A, for example, then it would not matter that the breaker was smaller than the installation manual requires. If they used wire rated for 40A and put in a 40A breaker the wire would get hotter than 50A wire on a 50A breaker would right up to the moment that the breaker tripped.

And, of course, aluminum wire of a particular gauge cannot handle as much current as the same size copper wire.

Finally, if not done properly (with listed components and use of anti-oxidant on the aluminum before removing the oxide coating from it) the splice between the aluminum and the copper can suffer mechanical damage from relatively small heating/cooling cycle effects, making the resistance increase and the heating increase until the conductor melts or a fire starts. The NEC and UL have very specific requirements for splicing Al to copper.
 
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As far as the Code addressing the issue:

110.14 Electrical Connections. Because of different characteristics of dissimilar metals, devices such as pressure terminal or pressure splicing connectors and soldering lugs shall be identified for the material of the conductor and shall be properly installed and used. Conductors of dissimilar metals shall not be intermixed in a terminal or splicing connector where physical contact occurs between dissimilar conductors (such as copper and aluminum, copper and copper-clad aluminum, or aluminum and copper-clad aluminum), unless the device is identified for the purpose and conditions of use. Materials such as solder, fluxes, inhibitors, and compounds, where employed, shall be suitable for the use and shall be of a type that will not adversely affect the conductors, installation, or equipment.
 
cruzader: You may be making a basic EE error in how breakers are applied to building wiring.

A breaker alone will not guarantee that a conductor is not overloaded. The breaker in combination with the load characteristics is what protects the wire from overload. If you have a 40A rated conductor on a 40A breaker with a load drawing 50A, that breaker might _never_ trip, or might take a very long time to trip. Do a search for 'circuit breaker trip curve' to better understand this.

Stove circuit ratings are also quite complex, because the peak KW rating of the stove will likely exceed the rating of the circuit...simply because the thermostatic control of the various elements virtually guarantees that the stove will not need its peak power on a continuous basis.

While I agree that a bad copper to aluminium splice was probably the major cause of issues with the circuit in question, if the stove requires a 50A circuit but was placed on a 40A circuit, then that could certainly contribute to overheating a wire.

-Jon
 
winnie said:
... If you have a 40A rated conductor on a 40A breaker with a load drawing 50A, that breaker might _never_ trip, or might take a very long time to trip. ...
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True, but a 50 amp load on the 40 amp conductor is also not likely to cause any major harm either.
 
aluminum wires are not time bombs waiting to explode and burn down your house. properly terminated they are as safe as copper. improperly terminated copper to copper splices probably cause more fires.

it is always about doing the work correctly.

who determined that the aluminum to copper splice was at fault?
 
petersonra said:
aluminum wires are not time bombs waiting to explode and burn down your house. properly terminated they are as safe as copper. improperly terminated copper to copper splices probably cause more fires.

it is always about doing the work correctly.

who determined that the aluminum to copper splice was at fault?
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True for today's aluminum wires, which are actually alloyed with a little bit of copper (I'm pretty sure it's copper), but back in the days when pure aluminum was used, it caused a bunch of fires, or so I am told.
 
ggunn said:
True for today's aluminum wires, which are actually alloyed with a little bit of copper (I'm pretty sure it's copper), but back in the days when pure aluminum was used, it caused a bunch of fires, or so I am told.
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The power companies have used aluminum for many many years overhead and buried ... yes, alloys have changed for building wire since the major problems in the 70's, but PROPERLY terminated, it is fine ... and is some cases (particularly where weight is of concern), aluminum is superior to copper or silver.
 
Nycedreemz said:
Purple wire nutz!! :happyyes:
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I hope you are joking!!!

Unfortunately I see the purple Twisters used all the time for the connection of ovens. These wirenuts are rated for #10/#12 solid AL and #12/#14 solid CU conductors only. They are not designed for larger conductors or circuits over 20 amps.
 
petersonra said:
aluminum wires are not time bombs waiting to explode and burn down your house. properly terminated they are as safe as copper. improperly terminated copper to copper splices probably cause more fires.

it is always about doing the work correctly.

who determined that the aluminum to copper splice was at fault?
Click to expand...
There were and continue to be major issues with the 15 and 20 amp branch circuit aluminum conductors installed prior to 1974. The issue is the fact the wiring devices that were typically used with the aluminum conductors had steel termination screws. The expansion of the aluminum conductor and the steel screw is much difference. Each time the connection heated up, the aluminum would expand more and would be extruded out from under the screw a small amount. Over time this would result in a connection failure, which in some cases would result in a fire. No matter how well you did your work this would happen, of course if the original termination was not tight, it would happen much sooner. For the most part it would only happen on heavily loaded circuits.

The CO/ALR devices that came into the market the same the new aluminum alloy did (~1974) had aluminum termination screws to eliminate the issue.
 
Aluminum termination screws sound like a challenging mechanical problem. Are you sure it was not some other alloy with a similar expansion coefficient?
You could also incorporate a spring mechanism that would allow for expansion without extruding the aluminum.

Sent from my XT1080 using Tapatalk
 
I know of a company that does a lot of AL to CU pigtails on older homes with a crimping tool and a special splice. They charge $50-$100 per opening/single gang and have done a tons of homes out here. From everything that I've seen this method is probably the best way to do this without having to re-wire a house with making it safe. Yes the purple wire-nuts work to, but like everyone said not for 50amp loads and I don't even know how you could get the wire into one of those if it was 40/50amp feed. I remember back when doing resi work some appliance would say "Copper Connections Only" but it seemed very popular that everyone pulled 6/3 AL to ranges.
 
GoldDigger said:
Aluminum termination screws sound like a challenging mechanical problem. Are you sure it was not some other alloy with a similar expansion coefficient?
You could also incorporate a spring mechanism that would allow for expansion without extruding the aluminum.

Sent from my XT1080 using Tapatalk
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You could be right...not sure. It has been a long time since I looked up what they did with the CO/ALR devices.
 
don_resqcapt19 said:
There were and continue to be major issues with the 15 and 20 amp branch circuit aluminum conductors installed prior to 1974. The issue is the fact the wiring devices that were typically used with the aluminum conductors had steel termination screws. The expansion of the aluminum conductor and the steel screw is much difference. Each time the connection heated up, the aluminum would expand more and would be extruded out from under the screw a small amount. Over time this would result in a connection failure, which in some cases would result in a fire. No matter how well you did your work this would happen, of course if the original termination was not tight, it would happen much sooner. For the most part it would only happen on heavily loaded circuits.

The CO/ALR devices that came into the market the same the new aluminum alloy did (~1974) had aluminum termination screws to eliminate the issue.
Click to expand...

this was not a 15 or a 20 circuit though, according to the OP.
 
petersonra said:
this was not a 15 or a 20 circuit though, according to the OP.
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It was not, but the issues that gave aluminum a bad name were, for the most part, the issues with the older 15 and 20 amp branch circuit wiring.
I would have to agree with you that for the larger aluminum wiring, the problems are mostly workmanship related.
 
curt swartz said:
I hope you are joking!!!

Unfortunately I see the purple Twisters used all the time for the connection of ovens. These wirenuts are rated for #10/#12 solid AL and #12/#14 solid CU conductors only. They are not designed for larger conductors or circuits over 20 amps.
Click to expand...
Yes just a joke:lol:, I'm well aware of the limits of the purple twister. Just trying to lighten things up.................Thought more people would have a giggle about it.
 
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