TrueDPD Control

Stefan Nickodem from Commercial Clearwater also asked about True DPD control using PPM instead of ORP which is not clearly stated in the manual.

When using the TrueDPD accessory on the MiniWarden or PoolWarden, you can control chlorine feed based on ORP, PPM, ORP w/PPM backup and PPM with ORP backup. Let me explain how.

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For simplicity, I will show how this is done in the quick menu. This doesn’t show all the features of the PPM programming.

To control with ORP only, program On If PPM<0.0

To control with PPM only, program On If ORP<000 and On If PPM<(0.5-9) enter whichever value you want

To control with ORP – PPM backup, use the ORP value you want to maintain with a PPM value set to the minimum PPM value you wish to maintain.

To control with PPM – ORP backup, use the PPM level you want which is greater than the minimum ORP level you wish to maintain. It is preferable to input an ORP value at least 20-30 mV below the ORP value displayed when you are at your ideal PPM and pH level.

NOTE: When using PPM control, your feed cycle with depend on the frequency of DPD test. 10,20,30 or 60 minute cycles. These cycles are based on the hour clock and not when it was turned on or programmed. (10 minute cycles will test 10 after, 20 after, 30 after, 40 after, 50 after and on the hour or 6 measurements per hour. 20 minute cycles will test 3 times per hour, 30 minute cycles will test 2 times per hour, 60 second cycles will test 1 time per hour.) For longer times between DPD tests, it is beneficial to use the ORP backup as the ORP reading is real time. Also note the PPM value you take with a test kit may not be the same as the controller is reading depending on how long it has been since the reading was taken.

To initiate a DPD test on demand, press 6 from the main display to enter DPD diagnostic display, then press 9 from the DPD diagnostic display to initiate the DPD test. You will see a counter going up on the bottom left next to CTR: as seen on the second image below. The test will take a little over a minute, then revert to normal operation.

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For outdoor pools with cyanuric acid, you can also activate the CYA offset feature found only in the PoolWarden Advanced Menu. This is not available in the MiniWarden. This allows the controller to automatically offset the ORP Set Point to compensate for the effects sunlight has on ORP readings. Depending on cyanuric acid levels, there can be a 20-50 mV swing in ORP at a given PPM/pH level. The higher the CYA level, the greater the swing. ORP levels will rise as the sun goes down and lower when daylight approaches. This programming will allow you to set Dawn/Dusk Hours as well as the offset number. ORP-CYA Offset helps maintain more consistency in PPM levels, especially when using ORP only control.

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