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Old 09-22-2012, 10:54 AM
Kiril Kiril is offline
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Join Date: Jun 2007
Location: District 9 CA
Posts: 18,365
Originally Posted by JimLewis View Post
Actually, the historical weather data is used for solar radiation, wind speed, and relative humidity.
For your reference Jim.

Originally Posted by JimLewis View Post
Out of the 5 weather factors used to create the E.T. formula, the temperature and rainfall are by far the biggest part of the equation.
Solar radiation, wind and saturated vapor pressure are the primary driving factors for ET. Rainfall is not considered in any ET formula.

Originally Posted by JimLewis View Post
So you could actually find a zone up here in the US that was very similar to the zone you have in Brazil and use that, if this controller doesn't have the capability to work with a southern hemisphere coordinate.
Maybe, maybe not. Without about a decades worth of historical data to compare you wouldn't have the information you need to make that decision.

Originally Posted by JimLewis View Post
For instance, let's say you're setting up a zone that has spray heads. It's going to ask you what the net precip. rate for that spray head is. So your zone has all RB 10' MPR nozzles on it. And you're operating at 30 PSI. so according to the RB literature, the precip. rate for that nozzle, with triangular spacing, is 1.75 in/hr. So that's what you enter, right? WRONG! They're asking for NET precip. rate. A spray head is only about 70% efficient. So you have to multiply 1.75 x .7. The result is 1.23. So your NET precip. rate is 1.23". THAT'S what they are asking for. But most people would either leave it at the stock setting or enter 1.75. Problem is, that's not correct. It's really 1.23. So if you've entered the wrong number in here, you've messed up the programming by up to 30%.
Net precipitation is determined by running an audit, anything beyond that is a guess, including assumptions of efficiency. That said, allowing for some system inefficiency is better than using controller defaults.

Last edited by Kiril; 09-22-2012 at 11:03 AM.
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