A Conditional Heat Port is enabled when the Use Heat Port boolean parameter is true (checked). When the heat port is enabled, a small red square, representing the heat port, appears on the icon.  The heat port can be connected to other heat ports or to thermal components.

When enabled, the heat flow out of the port equals the electrical power generated inside the device.  The temperature of the heat port, which is determined by the connected thermal components, sets the operating temperature of the component.

When disabled, the operating temperature of the device is given by the T parameter of the component. The default is 293.15K (20C).