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  #55  
Old 06-19-2009, 01:17 PM
Kiril Kiril is offline
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Join Date: Jun 2007
Location: District 9 CA
Posts: 18,318
Quote:
Originally Posted by JimLewis View Post
The thing is they can get E.T. dialed in pretty dang close just by using historical wind speeds (per month) for your zip code. Take a look at the SWAT testing they did on this unit. Most zones were off from what actual E.T. was by around 1.5%. The very highest zone in the test was off by a little over 6%. That's better than almost every E.T. product out there - and WAY WAY WAY closer than what we've all been getting with traditional time-based controllers. So when you're getting that close with your unit, is it really worth spending an extra $450.00 just to get a tad closer????
I know I have said this before, but I will say it again. Don't put a lot of faith in the SWAT testing. Beyond that, given most landscape plants do not even have a determined Kc, or ETc, stating ET percentage variance is more than a little misleading.

Quote:
Originally Posted by JimLewis View Post
I think the consensus was that they can get pretty dang close just using historical wind speeds rather than having to spend the money on something to measure exact current wind speeds.
I seriously doubt wind speeds used by this controller consider the influence of site vegetation and buildings on wind speed and direction, both of which can have an enormous effect on AE. A well chosen location for the weather station and an anemometer would go a long way towards maximizing AE.
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