Hi all,
I did another test today. 5 gallons of water, condenser lid on but sprayer off, heated to a boil. Then, I took off the lid, and..... it dropped, down to at least 203 before I stopped the test. Well, it looks like my burner isn't putting out enough heat to maintain a boil with the lid off, which also fits well with Spike's theory that the entrapped steam may be necessary to maintain the boil I was seeing before.
Why didn't I notice this before? Because this current setup is fairly new, and previously I was using a different pot that had Refletix insulation. I've brewed with this setup since I got the new pot, but I typically have left the lid on until the boil was reached, then removed it, and I suppose I wasn't actually checking the temperature to confirm it from that point on. There was always still evolution of steam bubbles and the wort moving around a bit, I just didn't realize that it wasn't actually at true boiling temp. It still made beer, though. Also, I have no doubt that a bit of insulation on this pot would also give me the few extra degrees I need to keep a vigorous boil going with the steam condenser running. But, I really don't like the insulation, and given that I'm just barely reaching my goal anyway, I think it's time to graduate to a higher wattage induction cooktop. I just need to wire a 240v outlet in my garage first...
Also, for those of you who asked what the spray pattern coming out of the Spike nozzle is like, behold:
Spray pattern video. Apologies for the portrait aspect ratio.
Does this look at all like the spray on your high PSI nozzles?
Thanks to everyone who helped me get to this point. I appreciate your great suggestions and experience!