Carbon Cycle Chemical Reactions Involved: Photosynthesis: Air and water molecules and the energy from the sun to produce a simple sugar such as glucose and oxygen molecules as a by product. During photosynthesis plants use carbon dioxide and produce oxygen.
Similar to shore power for ships, a ground power unit (GPU) may be used to supply electric power for an aircraft on the ground, to sustain interior lighting, ventilation and other requirements before starting of the main engines or the aircraft auxiliary power unit (APU).
So to ensure that it's able to get the power it needs consistently, the fan needs to be paired up with an A/C Fan Relay. This device is what your air conditioning system uses to establish control over the flow of electric current coursing through its fan. The moment the A/C system is switched on, this relay permits the proper amount of current to pass through one of its line to activate this device.