I am having a little problem trying to decide how to properly set the primary D/T on a P/S plumbed boiler. I replaced the primary pump on the Alpine 80 with a Taco Bumblebee as the pump curve showed it matched very closely what I was looking for. I wanted to get a 35* D/T across the boiler so as to maximize efficiency. The bumblebee's flow indicator is WAY off. It should be in the range of 4.2GPM when set the constant speed #2, which it is. The flow indicates 9.8GPM. My confusion comes from how to set the primary D/T when set to high fire in reguards to the zones. Should all zones be running or not?