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Wiring for lamp

jyang949's picture

After all the receptacles and switches I've replaced, I'm used to seeing 14-gauge wire in the walls. But what about wires inside a lamp?

We need to replace an outdoor light fixture. The specs for the one I like says "Electric lights supplied with 18/2 wire with ground." Is this okay? 


The wires inside a light (post #210137, reply #1 of 3)

The wires inside a light fixture are generally smaller than the "house wiring" feeding them.  Standard table lamps and "light duty" extension cords will normally use #18 wire, "medium duty" extension cords and perhaps some multi-lamp fixtures will be #16.

But it's my understanding (perhaps wrong) that "wired in" (vs plug-in) fixtures would normally have wire no smaller than #16.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

it's okay (post #210137, reply #2 of 3)

The light fixture itself has 18ga stranded wire.

The house wire in your walls that enters the junction box the light will be attached to should be fed with 14ga or 12 ga wire, typically romex. Your house has 14ga.

While some light fixtures now have built-in connectors already attached to the 18ga wiring that allow you to "stab connect" the fixture to your house wiring, you'll typically connect the 18ga stranded wire of the light fixture to the 14ga solid copper wire in your juntion box with wire nuts.

There are 10 kinds of people in this world; those who understand binary and those who do not.

Fixture wires are allowed to (post #210137, reply #3 of 3)

Fixture wires are allowed to be smaller than what you see in the wiring of your home. This is because they have a known load. 18 ga is good for 7 amps and 16 ga is good for 13.

Since the largest bulb you can normally get with an Edison base is 250w (a tad over 2 amps) any fixture with up to 3 sockets will safely fit into that 7a limit for 18 ga fixture wire.

In addition to that, most fixtures (luminaires) will have a maximum lamp size specified that is significantly lower than 250w.

In the case of a short (bolted fault) 18 ga is plenty to trip a 20a breaker in the lengths you would see in a lamp or luminaire.

U/L stopped listing 18ga extension cords years ago but there are still some old ones out there so use them carefully or just throw them away. They also will not have polarized plugs..