Thanks for the info. I purchased the tank and pump only. My Arduino controller will toggle the 24 volts via a relay when the pH level gets high as measured by my ioPool ECO monitor every 15 minutes. My Arduino controller also controls the pump and SWG so I can turn off the SWG when dispensing acid and also make sure the pump is running while dispensing acid. The good news is that since the Arduino is controlling the acid pump relay, I can have it dispense only the amount of acid that is needed. The trick is to figure out the acid pump run time for each tenth of the pH level. But once I get that dialed in, I should be able to maintain a constant 7.4 pH level as long as I keep acid in the tank.
Wow, that sounds fantastic! Keep us posted.
I'm gunna guess you already have thought of some or all of the following, but just in case, if it helps:
- When the IntellipH controller "turns off" the SWG so that it can dispense acid, it doesn't actually power the SWG down. It sets the SWG output to zero, dispenses acid, then restores the SWG output to its previous setting. That avoids the 5-minute SWG startup process each time the acid is dispensed. Perhaps your plan can mimic that, if it doesn't already.
- Another safeguard is: no matter what the output setting of the IntellipH is, you can't override that. So that it will only dispense X amount of acid during any given dispense command. This is so not too much acid can be injected at any given time. Adding something like that to your Arduino logic would safeguard for a wacky pH sensor reading asking the Arduino to dispense a crazy amount of acid.
- And the most important safeguard is: the IntellipH is monitoring the SWG's flow switch, and won't dispense acid when the SWG reports no flow. I recommend you include a manual flow switch in your setup, one that your Arduino can monitor, so that it won't inject acid with a no-flow reading. This would be in addition to however you have the Arduino sensing "pump running." Depending on how you're doing that, a "pump running" indicator might not actually mean the impeller is moving water. A redundant, mechanical flow switch to ensure flow is safer.
- An annoying safeguard is: the IntellipH controller also monitors the SWG's temperature sensor, and won't dispense in cold water. Where I live the pipes can't freeze, so I developed a circuit to override that safeguard in the winter months. Your setup won't have that limitation, so that'll be nice.
- And my ultimate safeguard is: I first mix my 31% acid with water in the tank, 1:1, so that there's only about 15% acid in there. And I only do so about a gallon at a time. So there's never any more than 1-1.5 gallons of 31% acid in the tank. That way, even if there is a catastrophic failure with my IntellipH controller, and it pumps the tank dry, my pool will only be subjected to a gallon of acid or less. That'll crash the pH, but not create a danger to swimmers or pool gear. Folks hooking up a 15 gallon Stenner tank full of acid to whatever they come up with for automating their acid pump are just asking for trouble (IMO). Pentair recommends this dilution anyway, to help prolong the life of the parts that can succumb to the constant acid exposure.
I love my IntellipH setup, especially the tank, because it's really well designed. Good to hear you're starting with what I think is the best tank available (for all its many features).
OK, that's enough unsolicited advice for today. Let me know that you know about the acid vent on your new tank, and that you know how to use that, before I go into ADVICE PHASE 2.
