When you plug it in (120VAC or 12VDC), there is about a half second delay and the fans spin up. They are LOUD. My PCP has a 250cc tube and goes up to 250bar (3,650psi). I usually fill from about 1,800psi back up to 3,650. It takes about 6 minutes and shuts off automatically. I can't see what the water system is actually doing, but the temperature display has yet to go over 28°C during a fill. The room temp was 17°C. It took about a cup of 50/50 antifreeze/water mix to fill the system and I have yet to see any indication of flow even with the cap off. I didn't get an owner's manual in the box and their customer service, online got me an electronic copy in no time. So far, very happy.