r,
Right, coming back to me now that you're building a "smart" system.
If you want to pursue this safety feature, and
if you can't bend the IC to your will to cooperate, how about this? Your system could monitor pH constantly (or periodically), but instead of dosing on demand, it instead just
queues the need for a dose. Then performs the dose at scheduled "safe" times. Like a few minutes after pump startup, or x number of periods during the pump run that a schedule pauses the IC (using the "spa method" I described).
Ideally, of course, you reverse-engineer whatever the IpH is doing to pause the IC, but in case you can't, this could be one possible workaround.
Your system could easily shut off the IC, I'm sure, but then the IC would have to repeat its startup process each time. Not the worst thing, but not as "cool" as the pause command the IpH can initiate.
I'm 50-50 in Jim's camp. I pretty much ignore the notion of waiting 15-30 minutes between doses of chlorine and acid, for the very reason he states. If I dumped in a cup of acid in front of an active return, it'd be almost impossible to ready a dose of chlorine and pour that into the same spot fast enough to get any sort of chemical reaction out of 12K gallons of water! So if I pour in LC a minute after dosing MA, I don't think twice about it. (I'm sure the bird that fell out of the sky and dropped dead that one time was just a coincidence!

)
That said, the warning NOT to do that is well supported here at TFP, so
somebody thinks mixing the two in pool water is not a good idea. Pentair thinks that (based on the safety feature they engineered into the IpH). If it actually
could be a problem, then certainly injecting acid a few inches in front of an active IC has got to be a sure fire way to reveal it.
Or just as likely this could have been one engineer's unscientific notion? Or an edict from Pentair's legal staff?
Now, I once did forget to rinse the last few drops of MA out of the measuring cup I use to dispense both MA and LC. The subsequent pour of LC into that cup definitely fizzled right up and produced some sort of gas. So that part of the narrative seems to be real...
*** Now for all you TFPers out there that are eavesdropping on this conversation, I was just kidding. DO wait a good while between doses of liquid chlorine and muriatic acid!! I always do! I swear!! And DON'T use the same measuring cup for both chlorine and acid. I never do that!! Wait... what?... Oh, right... My lawyer said to say that my lawyer didn't make me say that. Wait... what? Don't write that? Which part? Sheesh.
PS: here's another condition for you to consider: maybe don't inject acid after 30 minutes before end of pump run. I consider this myself in my scheduling. I don't want any acid entering the pool minutes before the pump stops. It's a long shot that doing so would cause any real issues, but I like the idea of my pool circulating for at least 30 minutes right after I dose anything, especially acid.