How to find the phase shift (the horizontal shift) of a couple of trig functions Graphing Sine and Cosine with Phase (Horizontal) Shifts, Example 2. In this video, I graph a trigonometric function by graphing the original and then applying the phase shift.
Take the electric hot-water heater recovery times and divide them in half to get the recovery time for a gas unit. Water coming into a 50-gallon tank at 40 degrees takes just 53 1/2 minutes to reach 120 degrees. For 60-degree water entering the tank, calculate about 40 minutes needed for the water to reach the 120-degree temperature. For 70-degree water, it would take 33 minutes.
So if you want to know how long it will take for a water heater to come up to temp after being drained, you could use this generic number or calculate it out. BTU (if watts â Watts x 3.413) times recovery efficiency (see AHRI screen shot below) = pounds of water heated 1 degree.