Will I burn down my apartment?

May 26, 2005 12:33 AM

I just replaced a burned out bulb in my overhead kitchen fixture. The bulb that burned out was a 60 watter. I only had a 100 watter on hand. I know I'm hastening fossil fuel depletion, but am I also causing a fire risk? What about ignoring the wattage recomendations in favor of higher watts in table lamps?
posted by incessant to home & garden (16 comments total)

I avoid overloading my sockets, but I'm pretty paranoid about that kind of thing. The wiring is almost certainly robust enough to handle the higher current. Your major risk would come, I think, from heating up the lampshade too much. In the past, I've cooked a couple of lampshades crispy by overloading: they get a little browned and brittle over time, and sometimes there's an odor. I've never seen smoke or fire, though.

If you want more light, I'd recommend these. They draw less power, produce less heat, and put out more light.
posted by mr_roboto at 1:13 AM on May 26, 2005

You should be able to get energy saver bulbs of up to 28 watts, which produce the equivalent of a 150-watt normal bulb. They are more expensive, but if I remember correctly, the extra price is actually more than balanced in the long run by the lower electricity bill.
posted by Zarkonnen at 2:18 AM on May 26, 2005

It isn't the current it is the heat. I have seen the insulation (hidden between the fixture and the ceiling) literally charred when too large a bulb has been used and I have created brown burn marks on the inside of table lamp shades the same way. Who knows how much room for error was designed into your fixture. I would avoid 100 watt bulbs in this fixture, except as Zarkonnen suggests those energy saving bulbs which are just folded florescents. Check the bulbs because some must be oriented upright, and most do not work with dimmers.
posted by caddis at 4:52 AM on May 26, 2005

Most fixtures have a sticker somewhere on them that tells the maximum wattage bulbs you should use. If the sticker's missing and the fixture is ventilated and has a ceramic socket, you should be okay with a 100 watt bulb. That said, I've seen few ceiling fixtures that are rated for 100 watt bulbs. The same can be said for table lamps, but besides the type of sockets, the type of shade figures into the acceptable wattage .

As others have said, the danger here is the heat that a 100 bulb generates. You might not be old enough to remember, but they used to sell toy Easy Bake ovens that cooked with a light bulb.

Your best bet is to go with a compact flourescent bulb which burns cool, bright and economically.
posted by SteveInMaine at 5:52 AM on May 26, 2005

There are a few dangers to using higher wattage bulbs.

1) I'll disagree with everybody on the house wiring and say it depends: a 100 Watt bulb consumes almost an amp. Any house wiring can handle an amp so it's not an obvious danger. However if you replace the 60 Watt bulbs with 100 Watt bulbs in a large number you could exceed the current capacity of the line.

2) The insulation. A 100 Watt bulb consumes a lot more power and radiates a lot more heat. If you bake the insulation in some bulbs (I've found lots of bakelite fixtures that had degraded insulation) it degrades.

3) Lamp wiring. The lamps wiring isn't just the hunk of cord hanging off of it, there's also wiring inside the socket. I would think this would be fairly safe but I've never played with it.

4) Heat buildup. The bulb is radiating heat, shades, enclosures etc are all being subjected to this radiation. If it's a recessed light then so is whatever is around the light in the recess. It's less trouble to go without a light for a day or two till you can get to the hardware store than rebuild your house.

In general overly hot bulbs also don't last as long, so if your bulb is heating up because it doesn't have enough airspace around it for the wattage then it'll burn out faster. This isn't a risk I guess but sometimes costs speak more to people than flames and charred flesh.

I rely almost entirely on fluorescent lights now. The local energy provider even subsidizes them so I can get them for a couple bucks each.
posted by substrate at 6:23 AM on May 26, 2005

I've always wondered if those singed lampshades are as dangerous as they seem. Do they have a "good" fire rating, so that they are supposed to singe and yellow instead of burning your house down?
posted by smackfu at 7:05 AM on May 26, 2005

The current is not an issue. If there were enough bulbs to make it an issue the breaker would trip.

The temperature on the surface of a 100W bulb is not likely to ever get high enough to be a fire hazard in itself. It just doesn't get hot enough to be an ignition source.

In general temperature ratings are not based on ignition temperature, but on the temperature at which material begins to degrade (discolour, soften/melt, become brittle, dielectric breakdown, whatever). Of course this could lead indirectly to a more serious failure, including a fire hazard.

I had a failed ceiling light fixture that might be related to my using a 100W bulb. The rivet that provided electrical connection in the socket became carbonized. The connection was intermittent for a while, and then completely failed.

This might have happened because high temperature caused material to become brittle or high temperature expansion loosened the rivet. There are probably some other possibilities, some of them not related to the temperature at all.

While it was intermittent there was a fire hazard - arcing can cause very high temperatures. On the other hand the fixture and electrical box are pretty fire resistant, so it probably wasn't that dangerous.

Also interesting, when the failure occurred the room was not air conditioned, and the light would be on for many hours at a time, so the temperature was pretty much worst case.

Anyway, too much detail probably, but it might help you to understand where the rating comes from.

Oh ya, if you get good quality energy saving bulbs (I like the ones from Canadian Costco stores, I hate the ones from Canadian Ikea stores) the light is really very very good. They are bright, the colour looks nice... The only fault is that even the good ones need a few minutes to warm up before they provide full brightness.
posted by Chuckles at 8:45 AM on May 26, 2005

Your best bet is to go with a compact flourescent bulb which burns cool, bright and economically.

Yeah, but rooms lit only with such lights seem like the tunnels seen by the newly dead.
posted by Mo Nickels at 9:31 AM on May 26, 2005

Use this handy formula to figure out how long it will take for you to break even on the compact fluorescent bulb. Remember that an abused fluorescent bulb (as in one turned on/off very often) isn't going to show anywhere near the full 5 year lifetime advertised on the side of the box.

Days to savings = (Price of new bulb / (($per_kwh/1000 * wattage of normal bulb) - ($per_kwh/1000 * wattage of new bulb))) / Hours lights turned on per day

Let me give you an example for anyone living in Ontario, Canada:

($5 / (($0.05/1000 * 60) - ($0.05/1000 * 13))) / 3

Days to savings = 709 days, or 1.94 years.

To save the $94 advertised on the package ($47 per bulb), it would take:

($47 / (($0.05/1000 * 60) - ($0.05/1000 * 13))) = 20,000 hours @ 3 hours a day = 18.26 years.

Enjoy!
posted by shepd at 10:42 AM on May 26, 2005

That's nice shepd, but who pays $5 per bulb? When the Costco 60W equivalent bulbs are on sale they are less than $2CAD each. Not to mention the fact that $.05/kwh is a very low rate for electricity.

A couple of redflagdeals threads discussing CF bulbs covering price and performance of various models, although you will have to do some reading.

Now there is an interesting question about overall environmental impact... CF bulbs are so cheap only because they are made overseas, but electricity is made locally with all the added costs that entails. So it is possible that the environmental impact of CF lights is actually worse than incandescent. I think it is unlikely.
posted by Chuckles at 11:22 AM on May 26, 2005

Chuckles, you are dangerously incorrect on a circuit breaker protecting you from overcurrent conditions. My parents lost most of their house and posessions when an old organ short circuited and set the place on fire overnight. The fire inspector, and I was there, determined that the household wiring on that breaker actually started the fire. The organ was the root cause but the breakers did not trip before a fire started.

He said it wasn't at all unusual.
posted by substrate at 11:37 AM on May 26, 2005

In BC, rates are $0.06.

What do you pay in the USA?
posted by five fresh fish at 12:04 PM on May 26, 2005

substrate, I think you need to give more details before making accusations. Assuming the household wiring was installed to code, the breaker had the correct rating and the breaker was functional, it should not be possible for the wiring to cause a fire. A fire in the organ, apparently not what happened, being an entirely different issue.

Perhaps I am wrong, please provide a technical explanation for the mechanism that I am overlooking...
posted by Chuckles at 12:19 PM on May 26, 2005

Okay, I have re read... substrate, are you simply saying it is a bad idea to operate a circuit near its rating? I mean, of course the odds of a failure are going to increase as you stress it more, but the rating is the rating because it is rated to work.

So anyway, if that is the issue, then what do you consider acceptable loading on a 15A household circuit? Just telling people they should be scared isn't really useful.
posted by Chuckles at 12:28 PM on May 26, 2005

I have changed my mind a little...

You should not be relying on the breaker to tell you when you have overloaded the circuit. The breaker is your safety mechanism, it is supposed to be a back up, it is not your first line of defense. You should know how much load you are putting on a circuit, and you should make sure that you don't overload it.

My statement did imply that you could use the breaker as a gauge for when you have over done it. That is not correct!

(very very sorry for the three posts in a row thing... ARGH!)
posted by Chuckles at 1:40 PM on May 26, 2005

Chuckles, if you can believe it, for where I live, I was rounding *up*.

Last month alone, the move to freeze rates at 4.3¢ per kilowatt hour for consumers and small businesses cost $135-million, up from $110-million in December.
posted by shepd at 2:55 PM on May 26, 2005