I guess that I didn't describe the system very well;
I pump the water to both coils 24/7, so there is always heat in the two duct systems. In the spring, when the house gets warm, due to gravity heat flow, I close the ball valves on the branches going to the coil for the house living area. If a cold spell comes, I open them back up. Not a big hassle. There are no zone valves, nor do I want to go to that effort. I figured to just run the pump any time the house heatpump OR the basement fan/coil calls. It might sound dumb, but at least I would not be running the pump 24/7.
As of now: 8124 controls the boiler temp, but not the circulator. The circulator is wired from the same circuit supplying the boiler with power. There are add'l aquastats on the piping, but they don't control the boiler. One is near the basement fan/coil unit, and is set to bring it on for a dump zone, at 210*. The boiler has never had an overshoot hot enough to bring it on, although it does work if I set it lower [see note below]. If I cycle the pump, that one would need to move. I have two more near the coil in the living space duct. One locks the heat pump's compressor out with heat in the pipe, and the other brings the fan in the heat pump on for another dump zone at 240* [left over from my day of hand firing with bit]. Setting the system up as such allowed the heat pump's thermostat to control the heat pump's fan, as it would normally do. If I cycle the pump, I would have to move the aquastat that locks out the heat pump too.
Now, what steamup wrote and re-thinking made me realize that I'm pretty sure that I was wrong about the thermostat circuit for the basement fan/coil being 24v. Although the old honeywell control that I used on it does have a 24v transformer, I now believe that the thermostat controlling it sees no current. otherwise, my parallel circuit from the boiler dump aquastat to the TT terminals would not work. I'll test tomorrow to see if there is current there, but I bet not.
I'm showing what a dumb tin banger I am. I'm really weak on the control end of this stuff.