Future large spacecraft such as the Space Station will have high power dissipations and long heat transport distances. The combination of these two requirements dictate the need for a new heat transport technology. Boeing Aerospace developed an ammonia thermal bus (ATB) concept using two-phase ammonia as the working fluid. Instrumentation and control systems were used to verify system performance, protect personnel and equipment safety, and run the system. The ATB was robust; thus operating procedures were simple and fault tolerant. Test results demonstrated a maximum heat load of 22 kW, a controllable turndown ratio of 44:1, and the ability to control setpoint temperatures within the range of 30 to 90°F. This paper describes the ammonia thermal bus (ATB), test instrumentation and control, procedures for operating the ATB, and test results.