on 7/2/05: 2p ambient= 89F, 59%RH when powered vent fan kicked on;
ran till 4:15p when attic reached 95F;
energy= 1/6hp for 2.25h @ $0.05783 = $0.0162
attic= 3.67ft hi, 24ft wide, 39.1ft long. three 3x8 inch vents at 2 gable ends + six 10 x16 inch louvers on soffit at lower part of gambrel roof which is about bottom of 3 rd level floor --
conditioned space = 2133sf, 78F @ 63%RH trilevel
one 5000btu/h window a/c in office with one 400w computer, 225w monitor, scanner, 350VA UPS running since 6:30am, another 250 w computer running about half of same time.
sorry, the cfm rating on the powered vent fan is painted over -- about 14 inch diam sleeve. 1974 vintage
Wait... so you mean your attic ventilator has been working since 1974 without eating a motor?
My place was built in '81, and when I replaced the burned-out attic ventilator motor last year, it was clearly not the original that I was replacing. The subtle clue to me that these don't last all that long is that my local Lowe's had an exact replacement motor sitting on the shelf. The box was dusty, yes, but still... they had it.
Cem-bsee, I missing something.
Whats the problem? The 10c a day it costs to run in addition to the cooling costs versus running the cooling alone (which will have a higher load).
I'm not sure the attic needs to be cooled to 95 degrees but simply kept to around 100-110 would help.
Is there a problem?
Your electric rate is really cheap.
What's your question?
Congratulations of what looks like a pretty successful use of the power vent in your situation. Nice to see someone cutting on-times down to a smart number. And let me say how great it is to see people making measurements vs. talking about what may or may not be folklore (with my situation it's hard for me to tell). Have you posted before, what your temperatures would be without that fan?
I'm not sure how important it is, but your computer equipment doubtless pulls less wattage than the max rating of the power supply. I checked mine and it was a small fraction of what you might think. Used a $40 gadget called "Kill-A-Watt" which is handy and fascinating to have around.
Relative to my level of knowledge, you went awful fast from "1/6 HP motor" to your wattage. Could you explain that in a little more detail please? Were you able to measure or read the wattage directly?
Best wishes -- P. Student
ok , from what I gather from your post here , And since I was one that has questioned the use of powered attic vents--you are showing the actual cost of a powered attic vent and the difference it actually made temp wise in your attic.
In other discussions it seemed like the popular opinion was that power vents actually do very little to cool an attic compaired to the cost to operate one
I havnt checked the attic temp , but on a day like yesterday we had 99 degrees oat, the temp indoors without using the ac , fans or other cooling devices was 88 degrees
in every room. even rooms not directly affected by the afternoon sun were the same temp
By the time I get home from work the sun has set and the oat has cooled down (usually) at least 10 degrees so it seems like drawing that cooler air into the attic, would help reduce the temp indoors
In the past thread someone made the suggestion that I put a fan in the attic and I did, It didnt seem to make much difference though