Illustration: Ian Warpole
Ungrounded (2-pronged) receptacles means your home has no way to safely conduct stray current
9. Ungrounded (2-prong) Receptacles

What it means: Your house's wiring has no way to safely conduct any stray current that escapes the confines of the wires.

Code violation? No; grandfathered in. (Today's code requires grounded circuits and receptacles.)

Danger level: Minimal, as long as you don't use an adapter to fit a three-prong plug into a two-prong receptacle. Doing so could destroy the device you're plugging in, and increase the chance of electrocution.

Solution: Replace two-prong receptacles with properly grounded three-prong ones, if wiring allows it (see . Also, test all existing three-prong receptacles with a GFCI circuit tester to make sure they're grounded. Rewire any that aren't.

10. Plug Falls Out of Receptacle
What it means: Worn contacts in receptacle no longer grip the prongs firmly.

Code violation? No.

Danger level: High. Loose contacts can cause arcing, which can ignite dry wood and dust.

Solution:Replace the old receptacles as soon as possible. (A new one costs about $2.) Many homeowners feel comfortable doing this themselves. Electricians will charge about $8 or $10 per outlet, although there's likely to be a minimum charge for small jobs.

Old Wiring: Is It Safe?
Today's standard household wiring is a plastic-sheathed, insulated three-wire cable, universally known by the trade name Romex. But the vintage copper wiring in many older houses works just as well as the new stuff, as long as it's in good condition and hasn't been altered in a way that violates code. Here are some wiring systems you'll find in older homes.

Knob and Tube
The earliest residential wiring system has a cloth-covered hot wire and a neutral wire, which run parallel about a foot apart. Ceramic knobs anchor the wires to the house framing; ceramic tubes are used where wires cross or penetrate framing.

Caveats: Cannot be grounded or spliced into a grounded circuit. Its soldered connections may melt if too much current flows through them. Rewire or disconnect any circuits covered with building insulation; it causes this wiring to overheat.

Armored Cable (Bx)
The successor to knob and tube. A flexible steel sheath covers hot and neutral wires, which are insulated with cloth-covered rubber. The sheath provides a ground, so grounded receptacles are easy to retrofit.

Caveats: Sheath must be anchored securely to a metal outlet box. Check condition of insulation every five years or so; it degrades over time, as shown above, or if too much current is allowed to flow through the circuit.

Two-Wire Plastic-Sheathed Cable
An early PVC-insulated (Romex) wire.

Caveats: Plastic is easily damaged. Grounded receptacles cannot be retrofitted to this wire.

Where to Find It
Electrician: Allen Gallant
Gallant Electric
Waltham, MA

Aluminum-to-copper connector:
Twister #65
Ideal Industries
Sycamore, IL

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