I am getting ready to do a 3 tier propane herms system. What btu burner is everybody using? I have seen things ranging from 37,000 to over 150,000 for their boil kettle.
I (and many others) used banjo burners with a low pressure propane manifold. Guessing 100K BTU's each and it worked great. High pressure they are somewhere north of 200K BTU's
I sold my old system, but I think it took 15-20 to get up to a boil? I usually fired up the BK once I had a few gallons in there and sparged slow so by the time I had 6+ gallons of wort it was rising near boiling.