As a Controller Professional for over 15 years, I just wanted to chime in on a few things to help people try to get a grasp as to what ORP is, and what Your controller is supposed to be doing.
First off, ORP is NOT a quantitative measurement of Sanitizer...its a QUALITATIVE one; This simply means you are measuring how well your chlorine is working in a swimming pool.
With that in mind...you need to understand a few things about ORP:
1-ORP is Greatly dependent on pH: if you have poor pH control, all bets are off! your ORP control with be hampered by fluctuating PPM values, and you will be chasing a runaway train.
2-Your Chemical Feed pumps have ALOT to do with how well your controller performs: Think of your controller as a Porsche Sportscar...if you have poorly sized pumps, or pumps that are not designed for controller operation, its like driving with Tires for a Economy Car; You wont get the full performance that a Sports car is supposed to give you. If your pumps are Properly sized for your pool, Then Your Controller will fly like the Porsche would in the Autobahn! (Controller Manufacturers may Vary - if you're not making the grade, maybe you should seek help from someone who knows more about Controllers?)
3) Chlorine Levels will NEVER be steady on ORP control: Controller are designed to regulate the chlorine levels to meet the demands a pool may bring; at busier times, a chlorine residual may need to be higher...and the controller will compensate. If you have used controllers, and have complained that a steady Chlorine level is not what you are getting, You are now on NOTICE.
4) Not all controllers are alike!: Controller programming can vary greatly from unit to unit, but you need to understand that your controller is only going to be as good as the Company behind it. BEFORE you select a controller, check the reputability of the vendor. Unfortunately, the Brand may be a good one, but the service may vary greatly from region to region.
For more information on Water Quality Control, or any other Pool Related issues, Feel free to contact me at 201-378-3314.
-Clemente Rivera, Treatment Specialties