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Bosch Combi circulator stays on

Multiman Member Posts: 3
With a Bosch Greenstar ZBR...3A, circ pump is always on, even when unit is not firing for heat (May-Oct). On-demand DHW is fine. Should circ pump always be on? If I unplug the pump inside the boiler, the unit won't fire for DHW. Boiler came w/house, probably 10-12 years old. Two zone valves, neither is calling. If I (homeowner) understand right, constant circ can be an aspect of letting the boiler achieve its greatest efficiency, by only requiring minor heating to maintain heating temp. The manual has cautions against changing "Constant mode." One other thing: I disconnected the (optional?) outdoor temperature sensor, as the installer had put in where sun was shining on it, and it seemed to impair the functioning of the heating mode. Now it sends a constant error code saying that the temp sensor is disconnected. I don't think the one thing has anything to do with the other, but thought it worth mentioning.