Yes restricting the flow for an impeller pump does make it work less hard, as hard as that may be to grasp. However, I am also aware that works best for cool water. When restricting the flow of hot water, too much restriction can cause pump damage. And I have no idea how one figures where the limit is. In any event, at 0.66 amp as it is, I could run the pump and fans 24 hours a day for a week (a literal 24/7) and still have 50% of my battery capacity available.
![Smile :)](./images/smilies/econ_smile.gif)
The KISS principle might indicate that valves or whatever might be an extra expense / complication we don't really need. We'll make many decisions as the test progresses. Thanks.
But then it is a simple enough job to place a valve inline when using the flexy hoses and measure the current change and see what happens to heat output of the radiator. Or I could use a restriction disc placed in one of the hose end connections.