I know this question has generally been asked but every system is different and I’ve seen nothing like mine.
I have a tankless water boiler for baseboard heat with a separate electrical control panel for a three zone system.
I want to add a C wire, hoping I can just plug it into one of these slots. But can’t make heads or tails of it. There is a point marked C up top. There are other markings for CP ZC bottom right. The wires leading out of the top are the zone thermostats on two-wire systems. (Two zones are two-wire heat only, a third is heat plus AC and fan.)