Is Aluminum Wiring Safe?

Ben Giesbrecht

If you have spent any amount of time researching home electrical wiring and safety, you likely have heard an opinion or two about aluminum wiring. If you have ever cross shopped aluminum and copper wire for a project your bank account probably had an opinion on the matter too.

Stranded aluminum wiring 8 awg or larger is safe to use for home electrical wiring. The solid aluminum wire often used for standard 15-20 amp circuits in the 1960’s and 70’s is a potential fire hazard and a definite cause for concern.

While aluminum wire gets a bad rap from many remodeling resources, the reality is more nuanced. When used for the proper application, aluminum works as well as copper and can save you a significant amount of money.

Why is aluminum used for wiring?

While aluminum is not as good of an electrical conductor as copper, if upsized a bit it works just as well and has two major advantages. 

The first advantage applies only during installation: aluminum is light. Much lighter than copper even after upsizing to match the current carrying capacity of copper. This doesn’t matter so much after the wire has been installed but it is a nice bonus during the installation.

The second advantage is the main reason anyone considers using aluminum wire: cost. Copper wire is typically 4-5 times more expensive than aluminum. For example, say you need a 100 foot 100 amp circuit to power a new shop. Using aluminum wire for that circuit could save you $500-$600 on material costs.

What are the downsides of aluminum wiring?

With the cost savings mentioned above you might be wondering why don’t we wire everything with aluminum? Well, for a short time most home builders were using it everywhere. Unfortunately this exposed the shortcoming of the material for this application and led to the reputation aluminum wiring has today.

Before we go into the specific problems of aluminum wire, let’s quickly cover the major causes of electrical fires. Almost every electrical fire can be traced back to an overloaded conductor (wire) or a loose connection. The one we are concerned with right now is the loose connections. 

Loose connections effectively reduce the wire size to the amount of contact being made. This forces electricity to jump the gap under load. In the worst case scenario the result is sparks, heating wire past its melting point, and ultimately igniting the building materials around it.

Aluminum wire has 3 characteristics that heighten the risk of loose connections:

  1. Unless coated, aluminum tends to corrode. This causes high resistance connection points in the circuit.
  2. Aluminum expands and contracts enough with temperature changes to loosen connections if they are not proper screw-in lugs.
  3. Aluminum is brittle and can be easily broken if bent sharply.

These problems really show up when smaller (12 gauge) wire is used on standard outlet and lighting circuits. The many splices, poor connections from push in wiring terminals on outlets, and cracks formed from bending the solid wire on these circuits led to arcing, melted outlets, and sometimes fires.

Where can aluminum wire be safely used in your home?

Large amperage circuits with secure screw terminal connections are still great places to use aluminum wire in your home. Some examples are electric dryer circuit, electric range / stove circuit, air conditioning circuit, spa / hot tub connection, or the main electrical circuit to a backyard shop. If you need a circuit with 40 or more amps don't be afraid to consider aluminum.

My home has outlets / lights wired with aluminum wire, how can I make it safe?

There are techniques to pigtail copper leads from the aluminum wiring using screw terminals, however the problem is never completely fixed when going this route. The best way to ensure your home has up to code, safe wiring is to rewire your home and replace all of the outlet / lighting wiring with new copper wire.

Having electrical experts, such as the ones at Cosmic Comfort, rewire your home is not as daunting a task as it first seems. New wires are dropped in from the attic or crawlspace and in a few days your home has new wire and outlets with no other trace of the work that was done.