Which of the 3 zones heats the basement? What does that little dial in the water control compartment have to do with it?
Difficult to answer your question without your year and model number. If you have AquaHot, there are a couple of heat exchangers in the basement that are controlled with a manually set thermostat. They operate automatically.
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Basement heat with an AquaHot uses zone 2 and uses the thermostat in the basement near the water manifold (in my coach). There are two heat exchangers, one at each end of the wet bay. Bathroom heat uses the same zone. Bathroom thermostat controls the heat exchanger in the bathroom. Either thermostat will turn on the zone 2 pump.