On 7/24/2014 1:42 PM, Jeff Liebermann wrote:
On Thu, 24 Jul 2014 05:36:44 -0400, rickman wrote:

On 7/23/2014 11:22 PM, Jeff Liebermann wrote:
Probably a bit late...

From the current issue of Home Power magazine:
"Making the Most of Your Ceiling Fan"
http://www.homepower.com/articles/home-efficiency/electricity/making-most-your-ceiling-fan
The temperature of the motor was far higher than anything
else in the room, including windows exposed to direct sunlight.
Not only was the fan not cooling the people who weren’t in
the room, but it was also working as a little space heater.

Is this a joke article?

It's quite real. It's one of those short info articles that magazines
like to use for filler. I suspect that it might have been shortened
through over editing.

He lists some useful info and then draws faulty
conclusions.

I have to confess that I didn't read it thoroughly and criticially.
You're right. The article has problems.

I think the lead in line is a perfect example...

A ceiling fan can heat up to about 100°F when running

Wow! 100°F!!! That is pretty much nothing. The incandescent light
bulb in the same fixture is thousands of degrees and likely puts off
more heat.

Nope, they're about the same. A running ceiling fan will burn about
75 watts going full blast. A light bulb might burn about 75 watts.
Both convert most of the 75 watts into heat. It's the power
consumption in watts that's important, not the surface temperature. If
I place a sealing fan motor, and a light bulb, in two seperate
marginally insulated cardboard boxes, and let them run for a while,
the final temperature will be the same.

I think the case for the fan heating the room is a bit
overstated.

Yeah, probably true.

More useful would have been a simple statement of the
wattage of the fan. The comparison to the windows is totally absurd.

Yeah, also true. However, please remember the audience. It's mostly
home owners that are interested in alternative energy for their homes,
not engineers and energy professionals. For such an audience,
generalizations are useful.

That makes no sense. The window doesn't heat the room because the glass
is at 100°F, it heats the room because it allows radiant heat in.
Comparing the temperature is totally invalid and not useful in any way.


They let in direct radiant heat from the outside. I can assure you than
nearly any window in your house lets in more heat in the summer than the
fan puts off. The temperature of the glass has no bearing on the heat
coming in through the window.

True, if you assume uncoated glass. With a Low-E coating, much of the
IR is reflected. I can grind the numbers for how much later if you
want.

I would love to see some numbers.

--

Rick