I have observed the following. The heating system is 4 zones, with tankless water heater, L8124C aquastat, and the Beckett Heat Manager with the DHW temp. probe added. When a thermostat calls for heat the circulator will begin to circulate water but if the heat manager is in economizing mode the circulator will turn off if the boiler temp (per the thrmometer on the boiler) gets to approx 140 deg. The boiler will then stay in this state of burner not running, circulator not running (although the thermostat is calling for heat), and Heat Manager in economizing mode. This state will last several mins until the heat manager switches to Burner Enabled mode. Contacting Beckett they recomend the following aquastat temps -- high temp = 180, low temp = 160 and diff. = 10 deg. (even though the heat manager instructions state that low limit should be 150 deg. or lower). Either low temp setting still yields the same behavior. I am guessing what is happening is the aquastat control is detecting too low a temp which is causing the circulator to stop. Heat manager believes their is still enough heat capacity and therfore preventing the burner from firing. And the stalemate continues until the boiler has lost enough of its heat capacity on its own so the heat manager enables the burner. Is this normal operation with a heat manager? How can this be overcome?