Ask LiveJournal Electrician: light fixture maximum wattage?

[randomness]

We have this old swing-arm lamp that takes three position bulbs. The socket is stamped 250W 250V, but I can't tell if it's just describing the socket or if the wiring in the lamp itself is rated for 250W.

Most modern swing-arm lamps I've seen have a tag that says they're limited to 150W. I figured I'd ask around before I put a 250 watt bulb in it and started a fire. :)

Anyone have any thoughts?

Comments

[rmd.livejournal.com]

that is likely just the socket.

[jendaviswilson.livejournal.com]

If it came assembled and the whole thing has a UL stamp, 250 is fine. But seriously, 250 is blinding and super hot! 100 should be sufficient for lighting a large area brightly. Use a CFL anyway, and you won't have an issue.

[awfief.livejournal.com]

You can't start a fire with a higher watt bulb. If the socket sends 150W to a 250W bulb, you get a 150W light. That's how things like "dimmer switches" work -- they send less power to the bulb. The problem is you're going to start a fire because a 250W bulb is incredibly hot at full power. Can you even find a household 250W bulb that's not a flood light?

[chain saw with a magician (from livejournal.com)]

The stamp is ambiguous and could apply only to the socket. I have quite commonly seen such lamps with a sticker on the inside of the cone giving a much lower power rating than what the socket says.

You can draw your own conclusions from the gauge of the wiring. A table with some opinions on reasonable limits is here:

http://www.powerstream.com/Wire_Size.htm

From this, to support a 250W (~2.1 A) bulb, the wiring should be no thinner than 18 gauge. 18 gauge is common for lamp wire, so check, but it's likely to pass.

I guess that just leaves the stuff near the bulb itself as a potential problem. Unless some of it's made of plastic, it should be OK. If there's a plastic switch or something, that might be the limiting factor, and I have no easy suggestions for computing that limit.

[tfarrell.livejournal.com]

I think a 250 watt bulb is almost unbearably bright and you'd probably be more comfortable with less brightness. I also think 250 watts will run up your electricity bill, so even if you want that much brightness, you might be happier with something with the same light output but better energy efficiency, and that would likely mean a bulb under 150 watts of actual usage anyway.

[twannger.livejournal.com]

Unless someone has rewired the lamp with a new socket, the stamp refers to the maximum possible bulb for the entire unit. Anything less won't be a problem.