USB-C Powering Electronics and its Circuitry
Not sure about your "the USB-C wall adapter", but if it is compliant to USB Type-C specifications, you will NOT have any power. Per Type-C specifications a Type-C port will NOT output the VBUS until a cable-device connection is made. If there is no Rd on consumer side, the port (charger) will not sense the connection and will not power the link.  

More, not every Type-C port or charger is capable to output 15 W (5 V 3 A). You can't just assume that your device can get 3A from any Type-C port. Ports can be 500 ma, 1.5A, and 3 A. This information is encoded by value of Rp resistor, 56 k for 500 mA, 22k for 1500 mA, and 10k for 3 A. To ensure that the port is 3A capable, your device should measure the voltage created on its Rd resistor, and only if the voltage is above 1.31V, you can take 3 A. See this topic for more explanations.