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Electrical Wiring FAQ (Part 2 of 2)
Section - Aluminum wiring

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	During the 1970's, aluminum (instead of copper) wiring became
	quite popular and was extensively used.  Since that time,
	aluminum wiring has been implicated in a number of house fires,
	and most jurisdictions no longer permit it in new installations.
	We recommend, even if you're allowed to, that do not use it for new

	But don't panic if your house has aluminum wiring.  Aluminum
	wiring, when properly installed, can be just as safe as copper.
	Aluminum wiring is, however, very unforgiving of improper
	installation.  We will cover a bit of the theory behind potential
	problems, and what you can do to make your wiring safe.

	The main problem with aluminum wiring is a phenomenon known as
	"cold creep".  When aluminum wiring warms up, it expands.  When
	it cools down, it contracts.  Unlike copper, when aluminum goes
	through a number of warm/cool cycles it loses a bit of tightness each
	time.  To make the problem worse, aluminum oxidises, or corrodes
	when in contact with certain types of metal, so the resistance
	of the connection goes up.  Which causes it to heat up and corrode/
	oxidize still more.  Eventually the wire may start getting very hot,
	melt the insulation or fixture it's attached to, and possibly even
	cause a fire.

	Since people usually encounter aluminum wiring when they move
	into a house built during the 70's, we will cover basic points
	of safe aluminum wiring.  We suggest that, if you're
	considering purchasing a home with aluminum wiring, or have
	discovered it later, that you hire a licensed electrician or
	inspector to check over the wiring for the following things:

	    1) Fixtures (eg: outlets and switches) directly attached to
	       aluminum wiring should be rated for it.  The device will
	       be stamped with "Al/Cu" or "CO/ALR".  The latter supersedes
	       the former, but both are safe.   These fixtures are somewhat
	       more expensive than the ordinary ones.

	    2) Wires should be properly connected (at least 3/4 way around
	       the screw in a clockwise direction).  Connections should be
	       tight.  While repeated tightening of the screws can make the
	       problem worse, during the inspection it would pay off to snug
	       up each connection.

	       Note that aluminum wiring is still often used for the
	       main service entrance cable.  It should be inspected.

	    3) "push-in" terminals are an extreme hazard with aluminum wire.
	       Any connections using push-in terminals should be redone with
	       the proper screw connections immediately.

	    4) There should be no signs of overheating: darkened connections,
	       melted insulation, or "baked" fixtures.  Any such damage should
	       be repaired.
	    5) Connections between aluminum and copper wire need to be
	       handled specially.  Current Canadian codes require that the
	       connectors used must be specially marked for connecting
	       aluminum to copper.  The NEC requires that the wire be
	       connected together using special crimp devices, with an
	       anti-oxidant grease.  The tools and materials for the latter
	       are quite expensive - not practical to do it yourself unless
	       you can rent the tool.

	       [Note that regulations are changing rapidly in this area.
	       Suggest that you discuss any work with an inspector if you're
	       going to do more than one or two connections.]

	    6) Any non-rated receptacle can be connected to aluminum wiring
	       by means of a short copper "pigtail".  See (5) above.
	    7) Shows reasonable workmanship: neat wiring, properly stripped
	       (not nicked) wire etc.
	If, when considering purchasing a home, an inspection of the wiring
	shows no problems or only one or two, we believe that you can consider
	the wiring safe.  If there are signs of problems in many places,
	we suggest you look elsewhere.  If the wrong receptacles are used,
	you can replace them with the proper type, or use pigtails - having
	this professionally done can range from $3 to $10 per receptacle/
	switch.  You can do this yourself too.

	There's a useful article at

User Contributions:

In a fire protection circuit, circuts are shown witha no example 6,8,4etc. what it mean?these circuits are connected between smode detector,junction box etc
My daughter dropped a small necklace behind her dresser. The necklace crossed a plug terminal and shorted the receptacle.
I bought a new receptacle and installed the same. I still have no power I suspect there could be a bigger problem,this is aluminum wiring.
I've killed the breaker and call an electrician but am curious as to what happened.P.s. there is a dimmer switch on the same circuit.
Regarding new construction wiring and running 12/2 and 14/3 wire in the same box.

I have multiple switches to lights. Ran 12/2 and 14/3 into switch box and inspector wrote correction needed.

What should I have done instead?

thank you
Does a grounding electrode facilitate the operation of a OCPD, to clear a ground fault ?
Assuming you are installing two switches in a two switch box, you probably should have used 14/2 and 14/3 instead of replacing 14/2 with 12/2. If you are only installing one switch in a one switch box, you should only have one cable in the box.
P k
I prefer to use nothing smaller than12 awg /the smallest sized wire on a circuit determines the allowable ampacity
Ex: 15 amp-14awg. 12awg-20amp only rule for thumb other factors such as continuous load,heating and others if you do not know the safe NEC rules then please call a qualified journeyman Electrician better be safe

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Top Document: Electrical Wiring FAQ (Part 2 of 2)
Previous Document: Underground Wiring
Next Document: I'm buying a house! What should I do?

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Last Update March 27 2014 @ 02:11 PM