Temperature-regulation and limitation of liquid agents, and/or in case of the faulty operation of these, for keeping the temperature of the agent at a safe level. It can be used by appliance-manufacturers and their service-agents, for water-heaters, hot-water tanks, hot-water washers and other appliances with similar operating-principles. When the temperature set by the user (RB), or the factory pre-set temperature (WB) is reached, it will automatically change the switch-position, opening and closing it by micro-switching, i.e. it holds the temperature of the agent to be controlled at the required level within certain limits. In case of faulty, abnormal operation of the regulator, when the factory pre-set temperature is reached, it will automatically and reliably open the electrical circuit with micro-switching. Re-switching can only be made after the fault has been eliminated, in voltage-free condition, manually, after the temperature of the sensor-element has dropped to room-temperature (25 +- 5°C).