I am replacing several old mechanical 120V 2-pole thermostats each of which controls both a blower fan (which blows air over hydronic coils to push warm air into the room) and a single central circulator pump (which circulates hot water to each blower fan unit). To function correctly, the pump must run when any fan is running, but each fan only runs when its thermostat is ON.
Currently, both poles of each thermostat are turning on LINE voltage to both the corresponding fan and the central pump. As shown below:
I would like to replace these thermostats with new 2-pole smart thermostats (this unit: https://www.sinopetech.com/en/product/smart-double-pole-thermostat-for-electric-heating-3600-w-zigbee/) but it requires a voltage difference across the poles, so my plan is to wire one pole to hot for both the fan and the pump and the other to neutral only the fan:
I'm confident this should work, but the potential issue I see with this is that when any thermostat is ON, the hot leg for each fan will be energized (although a complete circuit wouldn't be present since the neutral would be open). Is this permissible by NEC and is it safe?