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2018 National Home Improvement Estimator, All Rights Reserved Page 412

The aluminum wire itself isn’t the problem. It’s the wire connections that are to blame. You don’t need to
rip out all the aluminum wire you find. But it’s prudent to check connections in a home wired with
aluminum. Electrical devices used with aluminum wire should be rated specifically for aluminum (usually
stamped CO/ALR or Al/Cu). Look for signs of overheating, such as blackened connections or melted
insulation. If you elect to extend an aluminum circuit using copper wire, your electrician will need to rent
a special crimping tool made just for the purpose. When crimped, the wire connection must be covered
with anti-oxidant grease.

Aluminum wire is still widely used for residential service entrance, though not for concealed wiring in
walls and ceilings. Wires run between the house and the public utility grid are larger in diameter and
require very few connections. That makes aluminum a good choice. For interior wiring, the price
advantage of aluminum over copper usually isn’t worth the risk or the extra trouble, though aluminum
wire with a copper coating is used in some communities.

Non-Metallic Sheathed Cable
Non-metallic sheathed cable, called Romex or “rope” by electricians, is the most common wire type
used in homes today. The NEC classifies it as Type NM cable. (Type NM-B cable is identical but has a
slightly-better temperature rating.) Romex has two or more insulated conductors and a ground wire, all
covered in a plastic sheath. It’s popular because it’s inexpensive and easy to install. You can use NM
cable in wall cavities where the wire is protected from physical damage and unlikely to get either wet or
hot. When it’s run through 2" x 4" stud walls, protect the cable at each stud with a metal plate to
prevent damage from nails. Romex cable can be stapled to studs, rather than attached with nail-on
hangers or supports. Most electrical codes permit the use of plastic (rather than metal) outlet boxes
with NM cable.

You can’t use Romex for exposed wiring on walls if it’s within 5' of the floor. But most inspectors will
approve Type AC (armored cable) for that purpose. AC is like Romex but includes a flexible aluminum
cover that protects it against physical damage. If the inspector won’t accept AC cable for exposed runs,
you may have to install conduit. Unlike electric cable, conduit includes no wire. It’s a protective tube
through which wire is pulled. Conduit is used in most commercial buildings and occasionally in
residences, such as in the service entrance mast where overhead wires terminate at the entrance cap.
Flexible (flex), EMT (electric metallic tube), GRS (galvanized rigid steel) and IMC (intermediate rigid
conduit) are the most common types of conduit. Flex is a hard metallic tube with enough flexibility to
snake through studs. EMT is lightweight but not flexible. GRS conduit is heavier. IMC falls between
EMT and GRS. Each of these types has specialized uses.