Correct Run time for RM Mixer ET calcs

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Glenn G.

February 04, 2017 19:47

Running tests using a single zone to learn how this works and understand correct setup before applying to a 22 zone irrigation system.

Based upon setup of the controller and watering schedule, seems the RM is not computing long enough run cycle to replenish the effect of Mixer calculated ET.

Any recommended changes, clarifications, or corrections greatly appreciated.

= General Info =
    Device: RainMachine HD 16
    Hardware Ver: 3
    Firmware Ver: 4.0.845

    Location: Dallas, TX
    Weather Services Used: NOAA, Wunderground (Station located 1500ft from Zone)

    Program: Setup to run 2 days per week for 45min at 06:00am
                   Watering Restrictions not configured.

= Zone Setup (Custom) =
       Precip Rate: 0.5 in/hr
       Appl Eff: 70%
        >> Effective Precip Rate = 0.5 * .7 = .35in/hr

       Field Capacity: 0.67 in

= Observations =

Day of Week                                   1        2        3        4        5        6        7

Sched. RunTime (min)                     0        0        0       45        0        0        45 
RainMachine Calc Runtime(min)      60       0        0       16        0        0        12
                                                (manual)

Effective Precip (inch)                   .35        0        0     .09        0        0        .07
       (Runtime/60*.35)

RM Mixer ET                                .04      .06     .07    .07       .06     .04       .07

   (from Setup>Weather)

My Expected Water Req                                          0.17                            0.17
(Sum of ET Prior Days)                                     (.04+.06+.07)               (.07+.06+.04)

 

 

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• Official comment

  

  RainMachine Nicholas February 07, 2017 07:58

  Hi Glen,

   

  In RainMachine, if you don't have Correction for Past/Forecast Correction enabled, the calculation done for today are based always only on the future data (from the today,  until next run date exclusive). In your examples you are looking into past instead of future.

  Also you need to take in account:

  1. Rain Sensitivity - rain amounts are reduced to this percentage 

  2. Available Water in soil - any extra water that wasn't required by plants. The needed water will be reduced by the available water amount.

  3. Crop Coefficient/Exposure Coef - the computed ET will be scaled with these coefficients ( for example day ET * 0.7 (if it's Lawn) * 0.85 (partial shade))

   

  This is what comes up in my mind by looking at your table for now.

   

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  Glenn G. February 08, 2017 01:06

  Nicholas,

  Thanks for the info. and perspective.

  Can you point me to where the Correction for Past/Forecast Correction is enabled.  Can't seem to find a "Correction for Past" setting.

  Using Firmware Ver: 4.0.845.

  I do have "Forecast Correction" enabled in the Settings>Weather screen.

  Thanks!

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  RainMachine Nicholas February 08, 2017 07:50

  Yes, "Forecast Correction" is the new name for "Correction for Past". What it does it looks from last run until today and computes the difference between ET known at the time of program run (on last run) and the best ET computed from weather received that day. For example NOAA updates forecast for current day every 4 hours, at the end of the day you have the best forecast available.

  Same thing for QPF but also if you have a weather service enabled with local weather station, it will use the reported RAIN instead of program last run known QPF.

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