Does dimming low energy lamps save much energy?

How do you know it only saves very little? Are you saying that when dimming a tunsten filament lamp only the light energy component is reduced and not the heat?

mark

In article , mark writes

It is true that light output falls off far more rapidly than heat when dimming incandescent lamps, expect (roughly): 50% dimmed, 75% power use,

For the o/p, my belief is that the dimming process will be far more efficient than for incandescents but I have no cite for this, it should certainly be the case for purpose built dimming electronic ballasts but I'm uncertain how effective the use of a conventional dimmer on an incandescent replacement low energy lamp would be.

Previous threads in this ng have cited figures showing a disappointing energy reduction. I used dimmers a lot assuming that it was saving energy. Unfortunately hooking up an energy meter to read the data from a wall-mounted dimmer would be a non-trivial task. But if no-one has any data perhaps I'll use an ammeter and voltmeter and take some measurements.

Peter Scott

On Mon, 16 Feb 2009 10:16:16 +0000 someone who may be Peter Scott wrote this:-

I wait with interest to see whether the usual suspects come along and make loud and long complaints about this assertion.

I fear you'll need a power meter - the current and voltage may be significantly out of phase with all the electronics + non-symmetrical wave-forms.

Can you tell me what sort of low-energy lamps these are that work with conventional dimmers please? (and where to get them)

I've a couple of chandalier type things with 200W worth of incandescants in which I'd really like to replace with CFLs, but they'd need to be dimmable..

Gordon

Actually, scratch that, I've just seen this:

Gordon

I would expect energy consumption will match light output for any fluorescent, at least to a first order. When dimmed below about 50%, it's necessary to provide power to heat the electrodes, and that might be significant in short compact fluorescents. Some dimming control gear does this all the time in any case.

I haven't actually measured the load, although I could do so when I get a spare moment.

Why?

The OP said he was "very happy". I'm certainly not going to argue that he's actually putting a brave face on hiding his unhappiness.

Sid

Why? It's a perfectly reasonable point in the context of the subject.

CFLs, like any fluorescent tube, dissipate power in 2 places

1. the ends of the tube
2. the long discharge path

Most of the energy used goes in the latter, and this is wha produces light. So for small amounts of dimming your energy use is pretty much proportional to light output. As you dim heavily, you still get a lot of power reduction, but not quite as much as proportional to light output.

There is another effect, that phosphor efficiency varies a little depending on light output, but not hugely.

In short these perform way better than tungsten filaments, in this respect, with energy the saving being almost as much as the light reduction you see.

NT

Could be both at once like a cubist painting!!!!

Make sure you check the size. The bases are a bit bigger than usual perhaps. I got mine from CPC at just under a tenner.

Peter Scott

Thanks. That was the comment I hoped to hear. Taking note of the earlier thread about phase difference, I'll drag out my second meter (wherever it is) and try to get a reading. Your comments sound most encouraging. I think, once dimmed, the colour temperature of 'warm' 2700K lamps is fine for me. But each to his own.

Peter Scott

Colour of fluorescents change as you dim them because the relative intensities of the spectral lines change. Different brands and types may well change differently.

They would but they all got stuck in a snowdrifts while going for plumbing spares to fix the frozen pipes caused by the global warming.

Nothing like as big a change as tungsten, though. To the point where I'm not really aware of it here.

Just open the window and let a bit of cold air into the room. That'll dim any type of CFL pretty successfully ... d;~}

Arfa

Any readings that you get *may* be pretty meaningless, as the electronic ballast in CFLs is a crude switch mode power supply which has a 'pulsy' and very likely asymmetric draw from the mains in the first place, and then to make things worse, you are hitting it with partial cycles from the circuitry in the dimmer. All of this may combine to produce a power draw which is of such an odd shape that the power meter is not able to make true sense of it to the point where it produces a meaningful reading.

Arfa