I’m reading “The Marriage of a Solar Heater and a Swimming Pool's Mechanical and Plumbing System” at h2otsun.com web site and I’m a bit confused about their statement:
I believe that when a panel is fully primed, there is no static head, just the dynamic head. In other words the pump doesn’t have to work to get the water to the highest point of the panel, since water going down balances that out. So pressure being lower than the height of the panel would still allow for the flow if the pressure is lower than dynamic head.“If we tie solar in where the pressure is lower than the height of the collectors then we can do a conventional solar installation in which case the collectors drain down at least somewhat when solar is off.”
What I don’t get is how the water would get initially to the highest point of the panel and close the vacuum breaker if “the pressure is lower than the height of the collectors”?
Am I being slow here?