Comments on: First pass on energy savings http://blog.airscapefans.com/archives/first-pass-on-energy-savings All About Whole House Fans + bonus opinions on energy. Thu, 12 Aug 2010 20:15:32 +0000 hourly 1 http://wordpress.org/?v=3.3 By: admin http://blog.airscapefans.com/archives/first-pass-on-energy-savings/comment-page-1#comment-36 admin Tue, 22 Jun 2010 17:54:38 +0000 http://blog.airscapefans.com/?p=282#comment-36 That is the estimated energy savings per year. That is the estimated energy savings per year.

]]> By: drowell http://blog.airscapefans.com/archives/first-pass-on-energy-savings/comment-page-1#comment-35 drowell Sat, 19 Jun 2010 04:33:22 +0000 http://blog.airscapefans.com/?p=282#comment-35 The "energy savings calculator" says "our Energy Calculator predicts the energy savings of your Whole House Fan . . . ," and gives a number; is that number annual savings, monthly savings or something else? Not clear. The “energy savings calculator” says “our Energy Calculator predicts the energy savings of your Whole House Fan . . . ,” and gives a number; is that number annual savings, monthly savings or something else? Not clear.

]]> By: admin http://blog.airscapefans.com/archives/first-pass-on-energy-savings/comment-page-1#comment-14 admin Fri, 30 Oct 2009 03:23:39 +0000 http://blog.airscapefans.com/?p=282#comment-14 As to whether the WHF would usually run at low speed; that will depend upon how you size your whole house fan. Ideally, yes, a whole house fan should be sized to provide quick relief (lots of air), but be able to throttle down for (most) nights at a very efficient rate. For this analysis, we made some assumptions that we believe to be reasonably accurate, like the delta T between inside and outside is about 10 degrees. To jump ahead to the last part of your comment, that would involve doing an 24/7/365 energy analysis of your house. The software is there (might need some tweaking for free cooling), but to be accurate you would have to "describe" your structure, insulation, windows, doors, outside shading to the software. There will be some cooling potential/energy analysis software that we are working on coming out shortly. Yes, most PSC (the usual type) motors do not unload well at all. Many, if not most motors are running at 30%-40% efficiency, ie. for every 1,000 watts of electrical energy in, 300-400 watts of mechanical work comes out.. It's a big <del>problem</del> opportunity. :-) As to whether the WHF would usually run at low speed; that will depend upon how you size your whole house fan. Ideally, yes, a whole house fan should be sized to provide quick relief (lots of air), but be able to throttle down for (most) nights at a very efficient rate. For this analysis, we made some assumptions that we believe to be reasonably accurate, like the delta T between inside and outside is about 10 degrees. To jump ahead to the last part of your comment, that would involve doing an 24/7/365 energy analysis of your house. The software is there (might need some tweaking for free cooling), but to be accurate you would have to “describe” your structure, insulation, windows, doors, outside shading to the software. There will be some cooling potential/energy analysis software that we are working on coming out shortly.
Yes, most PSC (the usual type) motors do not unload well at all. Many, if not most motors are running at 30%-40% efficiency, ie. for every 1,000 watts of electrical energy in, 300-400 watts of mechanical work comes out.. It’s a big problem opportunity. :-)

]]> By: sdsalsero http://blog.airscapefans.com/archives/first-pass-on-energy-savings/comment-page-1#comment-12 sdsalsero Thu, 29 Oct 2009 23:26:04 +0000 http://blog.airscapefans.com/?p=282#comment-12 I agree with your first two assumptions, but wouldn't the majority of the time (overnight) be spent on low-speed? Also, what's the "deltaT at night" -- the difference in temperature between the outside air and the inside air? I see that it's an average, i.e., you're accounting for the fact that both temperatures are going to change during the night. I'm curious what impact that has on your calculation. Also, do typical fans (e.g. your 2.5WHF) really use 90% of the 'full-power' even at low speeds? What I'd like to see is a pair of graphs showing the change in inside-temp, outside-temp, and energy use during the course of a summer day (full 24 hours) for both a traditional A/C setup and a typical whole-house fan setup. I agree with your first two assumptions, but wouldn’t the majority of the time (overnight) be spent on low-speed? Also, what’s the “deltaT at night” — the difference in temperature between the outside air and the inside air? I see that it’s an average, i.e., you’re accounting for the fact that both temperatures are going to change during the night. I’m curious what impact that has on your calculation.

Also, do typical fans (e.g. your 2.5WHF) really use 90% of the ‘full-power’ even at low speeds?

What I’d like to see is a pair of graphs showing the change in inside-temp, outside-temp, and energy use during the course of a summer day (full 24 hours) for both a traditional A/C setup and a typical whole-house fan setup.

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