# Spiral CF bulbs & maximum watt Ratings?



## dt78 (Apr 23, 2007)

I've seen a lot of people using spiral CF bulbs to make cheap lighting for their tanks, and I'm wondering if you have to use the equivalent wattage of the incandescent bulb when replacing the incadecent bulb with the spiral CF bulb or if you can use a more powerful bulb.

*For example:*


A Lamp has a rating of 60 watts max.
A spiral CF that is equivalent to a 60 watt incandescent bulb uses on 14 watts.
A spiral CF that is equivalent to a 150 watt incandescent bulb uses on 42 watts.

Is it ok to use the 42 watt spiral CF instead of the 14 watt bulb that is equivalent to the lamp's maximum wattage since it really only uses 42 watts and is under the maximum wattage for the lamp? Will it be a potential fire hazard?


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## tropism (Jul 21, 2006)

I'm only 99% sure of this, so I'd like to hear other opinions too (especially if any of you have electrical engineering experience).

If a lamp is rated for 60 watts max, then I think the reason would be that either the wiring can only handle so much electrical current through it, or (more likely) that it's a heat issue.

I'm not quite sure about the _absolute_ max when using CF bulbs, but here's my thinking. Say you have a 60 watt CF bulb and a 60 watt incandescent bulb. The CF bulb would not get as hot as the incandescent bulb. (The electricity can be turned into either heat or visible light... since the CF bulb makes more light at the same wattage, it will be making less heat than the incandescent bulb)

So as long as you stay below the *actual* 'max wattage' specified on the lamp (not the CF 'wattage equivalent') you should not have a problem with either too much electricity going through the wiring of the lamp, or too much heat being produced by the bulb.

One caveat -- if the lamp encloses the bulb so that there's no air circulation (unlikely) the heat may build up to the point that the CF bulb couldn't handle it. (It would be harming the bulb, not the lamp.)


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## NoSvOrAx (Nov 11, 2006)

Actual watts are the only thing that matters. 42< 60 so your good to go.

Also the spiral bulbs have alot of re-strike (lost light) if you can get the straight ones they work better.


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## hoppycalif (Apr 7, 2005)

You can get more light from a spiral bulb by making a simple reflector that surrounds the back half of the bulb, and better still, that keeps the bulb down in the reflector so the reflector extends past the exposed top of the bulb. For an example see http://www.aquaticplantcentral.com/...ects/45208-diy-mod-perfecto-10-gal-light.html
You can see how effective such a reflector is by looking up at the bulb in the reflector and noting how much more of the bulb surface you can see in the reflector - all of that surface is contributing to the light from the bulb.

I agree completely with tropism about how much wattage you can use. One potential problem is that some of the spiral bulbs can't tolerate the heat from being confined in any way. They just burn out quickly - a few weeks in my experience. That light fixture in the thread I linked doesn't get at all hot, just slightly warm, so I don't expect any problems with it.

Another factor - the wattage of a spiral bulb is proportional to the length of the spiral. So, high wattage bulbs have to be physically bigger, either in diameter or length, or both. That will prevent you from installing them in some fixtures.


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## dt78 (Apr 23, 2007)

Thanks everyone. That's kind of what I assumed too. I was just thinking of trying to build something for an old 10 gallon I have, mostly for experiance, but I don't want to spend too much on it. I have some old 60 watt max lamps I was thinking of taking apart to get the parts.

I have a couple of reasons why I asked this.


I guess I've just always wondered why people didn't use the bigger bulbs.

My wife got a 3-way lamp that supports a 50-100-150 watt bulb and has a special mechanism that shuts off the lamp if the total wattage exceeds 190 watts (kind of like a little breaker). When I attempted to use a 3-way CF designed to be the equivalent of the 50-100-150 bulb, the lamp didn't work right. It worked for the 50 setting and the 100 setting but when I tried to used the 150, it would shut down. When I used an incandescent bulb everything worked fine. 

The first thing is really just curiosity and made me think maybe there was a reason I don't know about and that I shouldn't try it. The second one is what is really confusing to me. Is there anybody that can answer why the lamp didn't work with the equivilant CF bulb even though it used less wattage?

Thanks for the help.


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## dt78 (Apr 23, 2007)

Thanks for the link *hoppycalif*. I have actually looked at this already, and like the results. The old 10 gallon hood I have came with two 15W incandescent bulbs in it. I have used the 10W CF replacents that you can get for them, but I would like it to be brighter as I'm starting to move on to planted tanks instead of just the fish only tanks I've always had.

One thing that I was curious about in your thread is that the sockets you used say 250V 660W max. What is the significance of the 250V? Isn't it just being used in a standard 120V outlet? I remember hearing once that it is ok to use a 250V for a 120W application, but not the otherway around, as it is designed to handle "up to" 250V. Is this the case?


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## hoppycalif (Apr 7, 2005)

I think most light fixtures of that type are made for up to 250 volts, that being the maximum voltage the insulation is good for. They are standard sockets as far as the female threads are concerned. The ones I used are the ceramic type, which are good for higher temperatures, which makes their maximum wattage higher as well. They cost the same as the plastic ones.


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