Illuminating the elephant

[unixronin]

There's an elephant in the middle of the living room that the lighting industry really isn't talking about.  Put simply, it's this:  Compact fluorescent lamps and Edison screw sockets do not get along.  And the problem is heat dissipation.

You see, the Edison screw base works tolerably well with incandescent bulbs, but it was designed for incandescent bulbs.  A CFL lamp is a lot more energy efficient than an incandescent bulb, yes, and it produces a lot less waste heat.  But it's where that heat is produces that is important.

You see, essentially all of the power dissipation in an incandescent bulb occurs at the filament.  That filament is connected to the base only by two very fine wires.  As a result, virtually all of the waste heat produced by the bulb is emitted by radiation through the envelope.  Very little of it is conducted back to the socket.

A CFL, on the other hand, while it produces much less total waste heat than an incandescent bulb, produces a large proportion of it in its base ballast.  And there's nowhere for that heat to escape to except by conduction straight into the socket.  The socket isn't designed to dissipate that much heat, so the center contact (which is usually nothing more than a piece of stamped beryllium copper if you're lucky, brass if you're not) overheats, loses what little spring temper it ever had, and collapses flat against the bottom of the socket.  Then the socket stops working, because you can no longer screw an Edison base bulb far enough into the socket to make a decent electrical contact with the base.

Now, as it happens, the Edison screw base is on its deathbed anyway.  It's being replaced by the GU24 twist lock base, a much better design that is not nearly as dependent upon spring tension to make the base contact.  The Energy Star 4.0 specification for residential lighting (PDF) forbids the use of the Edison screw socket, requiring the GU24 base instead.  Unfortunately, it's arguably being done for the wrong reason:  not because it's a mechanically better design (although we're fortunate that it is), but in order to ensure that it will be impossible to put an incandescent bulb into an Energy Star 4.0 compliant light fixture.

There is, however, a staggeringly huge installed base of Edison screw light sockets in the US.  Billions of them.  And over the next few decades, they're all going to have to be replaced — because when they stop making incandescent light bulbs (if memory serves, California has already outlawed them), and all the holdouts are forced to switch to CFLs, a lot of Edison screw socket light fixtures are going to overheat and fail.

I suppose it's going to be a good time to be an electrician.

Comments

[unixronin.livejournal.com]

LED lighting is coming, though general-purpose LED replacement light "bulbs" are still extremely expensive. I'm hoping they'll get a lot better and a lot more affordable within the next five years or so.

Like you, I've had a LOT of CFLs fail prematurely. I don't give a tinker's damn what the RATED life is; I'm not really convinced they actually last any longer in the real world than incandescents. And yes, ballast failure due to heat is part of that problem. Most CFLs carry a caution that they are designed to operate base-down, and operating them base-up may significantly shorten their life; but look at the light fittings in any house, and guess what, probably 90% of them are base-up...