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I recently moved to a new location where instead of the common E26 light sockets, they have GU24 light sockets. This is a bit of a problem for me, because I like to use edison-style incandescent bulbs, and I find their warm color and low luminescence most palatable for evening indoor lighting.

I checked the GU24 socket, and it says 660 W. But on the light fixtures there is a sticker that says "MAX. 13-watt. Risk of fire". I'm very new to home improvement, and I'm not sure exactly how to interpret this.

If I buy a GU24 to E26 adapter and install a 30- or 60-watt incandescent in it:

  1. Is there a risk of fire because the fixture can't handle the heat produced by a 14+ watt light bulb?
  2. Is there still a risk if I remove the glass fixture and just screw the light bulb into the adapter?
  3. Would a 14+ watt light bulb potentially cause overheating in the actual electrical wires/their plastic sleeves?

I've added a few pictures to show the fixture and the socket. The "MAX." sticker is attached to a plastic ring that keeps the glass fixture in place.

socket ring fixture

  • Have you tried LEDs on the "warm white" end of the world? (2700K color temp, or so) – ThreePhaseEel Aug 21 at 22:49
  • I think I have, and they're too bright for me. Edison-style light bulbs can output 200-400 lumens, they get even warmer than 2700K, and they also have an emission spectrum which is more pleasing to me than that of LEDs. There's emerging research on the relationship between light emission spectra and melatonin production/sleep quality, and the research suggests that low wattage incandescents may be best for the purpose of evening indoor lighting. – N4v Aug 22 at 20:42
  • Well, getting a LED setup to spit out 300lm at say 2000K should be manageable, no? (although that's warmer/redder than typical "warm white" binning by a significant margin.) – ThreePhaseEel Aug 22 at 23:26
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If I buy a GU24 to E26 adapter and install a 30- or 60-watt incandescent in it:

  1. Is there a risk of fire because the fixture can't handle the heat produced by a 14+ watt light bulb?
  2. Is there still a risk if I remove the glass fixture and just screw the light bulb into the adapter?
  3. Would a 14+ watt light bulb potentially cause overheating in the actual electrical wires/their plastic sleeves?
  1. Absolutely a fire risk. Generally things are designed to handle a bit extra, so a 15W bublb probably wouldn't be a problem. But 30W = > 2X - don't do it.
  2. Yes. The rating is based on "everything". You can't guess which parts exactly determine the problem without a lot of engineering calculations.
  3. The wires themselves? No. The wires are typically rated for 15A or 20A - i.e., 1,875W or more. The problem in this situation is the socket and connections.

As I understand it, the GU24 (or similar) has been mandated in some jurisdictions specifically to avoid people (like you!) using it for incandescent bulbs. If they installed E26 fixtures then it would be trivially simple to install a bulb that generated too much heat for the fixture and waste energy.

Take a look at the newest LED bulbs. They are available in quite a variety of CRI and are a far cry from the first CFLs and even the first white LEDs. If you save 25W x 1,000 hrs/year (< 3 hours a day) that's 25 kWh ~ a few dollars a year, more than enough to pay for a high-quality bulb. Plus in the summer you will save double because you won't pay to remove the heat generated by incandescent bulbs.

Seriously, there is a lot of good stuff out there. Many big orange or blue stores have decent lighting departments with samples of a lot of different bulbs so that you can actually see the difference. If that doesn't satisfy you, go to a real lighting store - i.e., one that sells to the trade (but most will sell to the public too) where the only thing they sell is lighting. Hanging an incandescent bulb may have been the best answer in the early days of CFLs, but there are much better choices now with quality LEDs.

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    Your #3, are you referring to the house wiring or the light socket wiring? – JACK Aug 21 at 15:45
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    House wiring. Socket wiring in this case is rated to at least the 660W of the socket rating. – manassehkatz Aug 21 at 15:48
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    Just asking because I've seen a lot of fixture wiring toasted. – JACK Aug 21 at 15:51
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    Certainly quite possible that overheating the fixture would result in the wiring right near the socket getting toasted before the socket itself. But with a properly designed fixture with a correctly sized bulb, everything should be OK. – manassehkatz Aug 21 at 15:58
  • I agree. They were definitely the wrong bulbs. – JACK Aug 21 at 16:09
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I get where early LEDs didn't make much of an impression, with their blueness and rather terrible CRI. That didn't just bother you, it also bothered people in the LED business. As a direct result, they fixed it. Very thoroughly.

Of course it's still possible to buy cheap, janky LEDs; in fact it's pretty easy. All the usual cheap outlets await. However for the discerning buyer, it's no trouble at all.

Incandescents are a firestarter here

The entire point of a GU24 fixture is to render it impossible to insert incandescent bulbs. And I know this seems like a big dirty government conspiracy, and I won't deny that energy conservation and pollution control have a slice of the pie. But a big part is manufacturers themselves are happy to be free from the thermal management challenges of building a fixture that takes incandescents.

Is there a risk of fire because the fixture can't handle the heat?

Correct.

What if I remove the glass fixture?

How about the wires / sheath?

We don't know because in this country, we have someone who answers those questions for us: Underwriter's Laboratories or UL. UL does all this testing on the fixture, and gives definitive answers to all these questions. However, the UL listing is contingent on the fixture being used according to its labeling and instructions.

(UL has competitors; CSA and ETL are common ones, and expect to see a file number as part of the label. CE is not one; it stands for "Chinese Excrement" and is found on the rubbish from Alibaba/eBay/Amazon.)

Because of that, a UL listing is required for fixtures installed in homes (NEC 110.2). And you are required to obey the labeling and instructions (NEC 110.3b). We here have had a lot of experience with the electrical codes (NEC) - and our experience is that every rule in there has a good safety reason for being there. There's no government conspiracy; it's written by a nonprofit. So the NEC is something we take seriously, and you should too.

Insurers agree, by the way; they'll refuse a homeowner claim if it's caused by an intentional violation of NEC.

Change the fixture

Fortunately, Home Depot has loads of fixtures with E26/27 sockets and rated for incandescent, that actually do have proper UL/ETL listings with file numbers. Buy one, put it up, have a field day with your incandescents.

This may violate some other codes, but they're not safety codes, so that's between you and the regulator.

Re-factor your circuit load

Another reason builders use guaranteed-low-power fixtures is it allows them to put more fixtures on a circuit. So, identify your circuits and re-crunch your numbers to make sure you aren't inadvertently putting 2300 watts of fixture on a 1440 watt circuit.

  • While it's true you can't use an incandescent with a GU24, it's also true that they make 50W GU24 halogens, which burn like the sun. – Machavity Aug 21 at 22:12
  • @Machavity Halogens are incandescent. Are you sure? I searched "GU24 halogen" and just got a bunch of raggedy search results like you get when searching for nonexistent things. Home Depot had 1 hit, but it was a 24-pack of GU10. – Harper Aug 21 at 22:43
  • It might be limited, but as I noted in my answer, I bought a fixture several years ago that was all halogen GU24 (it was from Home Depot). They may finally be phased out (found several "Halogen replacement" LEDs), but they were out there for a long time – Machavity Aug 21 at 22:47
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Without getting into how these fixtures are rated (you will find out soon) my answer to your three questions is "yes". Sockets will always have a higher rating than the fixtures that use them and it's the fixture rating that counts. Think of it like this: your car can go 100 miles per hour but you're on a winding road with cliffs on each side so the speed limit is 25. I wish I had a dime for every fixture I had to change because people used higher wattage bulbs than they were supposed to. In most cases it was the fixture wiring that failed.

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This is the surest sign of your 13W limit: the GU24 plate here looks plastic

Plastic holder

I bought a track light fixture for my previous house that had four GU24 halogen bulbs (50W). Those things got HOT. The socket, however, was ceramic inside a metal housing. It could survive the heat. Plastic here will not handle that.

  • Are you 100% sure the size was GU twenty-four? There are many GU sizes, it is basically the distance between stud centers in mm. – Harper Aug 21 at 22:49
  • I can't be 100% sure (I don't own the house anymore). There's an off-chance it was GU10. Same principle applies, tho. Ceramic base could handle it. This doesn't look ceramic. – Machavity Aug 21 at 22:59
  • GU10 has studs about 3/8" apart. GU24 is 1" apart. It's analogous to Candelabra vs Normal Edison. – Harper Aug 21 at 23:03
  • This makes sense, but the plate here (where it says "UL LISTED LAMPHOLDER 6G44"), also has 660 W written on it towards the left. Perhaps the 660 W is how much electricity the socket can handle, but it's not a reflection of the wattage of the light bulb to be installed in the socket...? – N4v Aug 22 at 13:34
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    The socket is probably telling you the watts the wiring can handle. For instance, Romex wire will tell you it can handle 600V, even though you're probably not going to have more than 240V running down any one given wire. – Machavity Aug 22 at 14:10

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