As I understand it what you have described is correct. The high pressure side will fill straight to the gun. It only starts working when your high pressure tank is below the desired pressure for the gun. I'll try to explain. I only fill my high pressure SCBA to around 3000 psi. This being , most of my guns require 3000 psi. So basically one tap on the fill switch and it fills the gun. As your pressure in the SCBA gets lower it will take more taps on the fill switch. So when my SCBA gets down to say 2500 psi it's gonna take 3 or 4, maybe 5 taps on the fill switch to top my gun to the 3000 psi. The actual boost is not going to come into play until you are filling your gun to more pressure than the pressure that is in the high pressure tank. When I had my Huben this worked great as my high pressure SCBA was at 3000 psi, but I filled my Huben to 3600 psi and the boost had to work to get the Huben up to 3600 psi. If my high pressure SCBA had been 4000 psi the boost would have not had to come into play and it would have been fed straight to the gun's reservoir until the SCBA pressure was lower than what I intended to fill the gun at? Hopefully someone can explain it better?
