How to turn off heat

Under normal operation, the thermostat controls heat. Presuming 24vac power is there, the t-stat and electrically powered zone valves are operational. The first image of a TACO zone valve is operated by thermostat. The metal lever attaches to the valve for manual operation if t-stat (24vac) power is lost; left/closed/no hot water circulation to baseboard heating, right/open valve/hot water circulation. The circulator pump is also controlled by the t-stat; on for heat, off to stop hot water circulation.

Home hvac systems are not diy friendly. Perhaps a professional plumber should be called to investigate this peculiar problem.

I'm not familiar with the bottom image, also a valve.