A salesman told me that solar collector panels with two–inch header pipes are better than models with 1–1/2 inch headers. Is this true?
No. The argument is that a two–inch solar collector panel header improves efficiency by allowing more water per minute to flow into the fluid passages of the heating surface. While it is true that two–inch pipe has a higher saturation (maximum) flow rate than 1–12 inch pipe, a single bank of solar panels is never installed with more than about 480 square feet of total solar collector panel area. (Larger solar systems are broken into multiple panel banks.) Solar panels designed for swimming pool heating temperatures function best at a water flow rate of about 1/10 gallon per square foot of solar panel surface area per minute. So for the best thermal performance, we would never want to flow more than about 48 gallons per minute (1/10 gpm per square foot x 480 square feet) through a single panel bank, regardless of the pipe size. 48 gallons per minute is well below the saturation flow rate of 1–1/2 inch pipe. Some solar collector panels require larger headers to partially offset the incre
