I just had a brand new PowerVent WH installed by a licensed plumber. It fires for about 5 minutes then shuts down with 3 flashes. Pressure switch failed open. Orders per manufacturer American new Pressure Switch. Doesn't work, eventually American sends their own plumber they cant get it to work. American allows me to replace the brand new WH with another brand new WH and pay for the new install at my expense. Still doesn't work 3 flashes. All 3 plumbers have left me on my own after paying $$$ and still no hot water.