There's a light on the the landing outside my back door (second floor
of a three-flat) which is useful for lighting the steps when I come
home in the dark. Since I must turn the light on before I leave so
that it will be on when I return, I would like to save electricity by
replacing the incandescent bulb with a screw-in fluorescent tube. I
wonder whether those tubes are safe and effective to use at very low
temperatures. I live in Chicago, where the annual low temperature is
typically -15 to -20° Fahrenheit.
Most of the CFs I see available today are rated for cold weather. Look
on the packing and some will indicate either a general note that they will
work in cold conditions or will list a minimum temperature.
"Temperature Effects on Performance
The ambient temperature around a CF lamp can have a significant effect
on light output and lamp efficacy. The temperature of the coldest spot
on the surface of the lamp is where mercury vapour will condense to
liquid form, and this temperature (the "minimum lamp wall temperature")
controls the vapour pressure inside the lamp. The optimum lamp wall
temperature for CF lamps is generally l00°F (38°C). At temperatures
below the optimum, mercury vapour will condense at the cold spot,
reducing the number of mercury atoms available to emit UV radiation:
light output drops. At temperatures above the optimum, an excess of
mercury vapour is present, absorbing the UV radiation before it can
reach the phosphors: light output also drops.
Low temperatures pose the greatest problems for CF lamps. Not all
compact fluorescent systems are equally susceptible to low-temperature
problems, but in general, as temperature drops, so does light output
and efficacy. At very low temperatures (below 32°F or 0°C), lamp
output can decline to one-third the rated value or less. It is
important to note that some CF lamps will have to warm up a while
before producing sufficient light under cold conditions, some may take
several minutes to ignite, and some won't start at all.
For cold applications (either indoors or out), choose CF lamps and
ballasts designed specifically for low-temperature operation. These
lamps are usually equipped with electronic ballasts and can be enclosed
in globes or recesses to prevent wind chill of the lamp. Even with
these precautions, it should not be assumed that the lamp will operate
at the same efficiency and produce the same amount of light as it would
under more hospitable weather conditions."
at this website: http://irc.nrc-cnrc.gc.ca/pubs/cp/lig3_e.html
sounds like incandescent might be a better choice, though if you're
worried about electricity consumption, you could look into retrofitting
a motion sensor so it only turns on when you come home and walk within
the sensing range (leave it switched so you can turn it off while home
and avoid it going on and off all night from cats or dogs or whatever
setting it off). I believe there even exist motion sensor adapters
that just screw into the socket and the bulb would then screw into the
adapter. No wiring, no other changes - just make sure it's rated for
I have done this for years, in new england,and they work, dimmer when
cold, really dim at startup. Probably shorter life, although I had a
flood type cf that is still alive after 5 or 6 years of use. just
replaced my current porch light after IIRC 3 years, but it might be
unrelated. Some of my 12-14 year old cfs are still alive
I any mildly enclosed fixture they will make enough heat to function.
Out in the breeze you might want to use one of the ones with a little
globe over it
hey a 60 watt light bulb on 9 extra hours every work day[60*9*250] is
135 kW of electricity a year,or 108 more than a 12 w cf, so it would
seem to payoff, at my business rate, 19 bucks a year.....
I use CF bulbs on my light fixtures outdoors. I live in SE MI. On
really cold days, sometimes it takes a few seconds for the lamps to
ignite and I have noticed that the light output is somewhat less. As
they warm up, the light increases. My light fixtures are open at the
bottom so at least some of the heat created by the bulb stays by it to
help with the temperatures.
The low power consumption and long life more than compensate for any
reduction in performance, IMHO.
I'll third that. I got tired of frequently noticing that one of more of
the three "flame shaped" candelabra based bulbs in our pair of front
door glass sided "lantern" fixtures was burned out. We're in Red Sox
country BTW. The bulbs were a PIA to change, I had to sttand on a short
stepladder to be able to reach down into the fixtures and do that.
I decided, "To hell with appearances.", pulled the fixtures down,
removed the candelabra sockets and put one standard base socket and a CF
bulb in each.
That was about seven years ago and I haven't had to change a bulb since.
That's cold, but things might not be as bad as the low temperature
indicates. If you can provide a small, nearly air-tight enclosure for
the bulb in cold weather, its own heat production may provide it better
operating conditions than if it were exposed.
During the day, the enclosure will also provide a greenhouse effect to
keep things a little warmer.
The Philips Marathon line of CFLs is rated for temperatures as low as
-10F (-20C). Philips offers a version that is enclosed in a clear
plastic cover called, appropriately, "Outdoor"; presumably this
variant would be a good choice if the bulb is used in an "open" style
fixture and thus directly exposed to high winds and extremely cold
temperatures. It comes in either 15 or 18 watts (roughly equivalent
to 60-watt and 75-watt incandescent, respectively).
I would definitely recommend you give it a shot. If it fails to start
reliably in extremely cold weather you still have two options -- one
is to temporarily replace it with a standard incandescent bulb until
temperatures return above -10F or, alternatively, let it run 24 hours
a day (once started and sufficiently warmed, it should continue to
operate without any difficulty).
Although this second option sounds wasteful, it is still likely to be
the better choice if you are away eight or more hours a day. A
15-watt CFL will use 0.36 kWh over a twenty-four hour period; that's
the same amount of energy consumed by a 60-watt incandescent bulb over
six hour period, or a 40-watt bulb over nine hours. With a rated life
of 10,000 hours (versus 1,000 hours for a regular incandescent)
there's also less likelihood that bulb will be burned out when you get
One other possibility is to replace your existing fixture with one
equipped with a motion detector but the economics of doing that would
be questionable. Assuming this 15-watt CFL operates an average of 10
hours each day, at $0.10/kWh, your annual operating cost is just
On Thu, 13 Jul 2006 16:04:54 GMT, Jonathan Sachs
In spite of what several nay-sayers have posted, several companies sell CFLs
that are rated to -20C or even -29C. They work just fine in winter conditions;
I've used them for years. Phillips, IIRC, has them rated to -20C. I don't
remember where I got the -29C lamp (well, Home Depot probably, but I don't
remember the maker).
A timer switch suitable for CFLs is a good idea to minimize the amount of time
the light is on. Alternatively, a light operated switch that will work with
My personal experience is that they will work, sort of. I have lights
in my garage. There are two pair. I have one tungsten light and one CF in
each one. That way in the winter I get light as soon as I turn on the
switch and better light a short time later. When it is really cold out and
about 0º F inside the garage, it takes a few minutes for the Cf's to come up
to close to normal levels. Note some older ones I had and tried did not
function well at all, but the new ones seen to do well in the cold.
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