​FMC Tower

The electrical system of the FMC Tower is housed primarily within the mechanical spaces in the basement levels, the transfer floor on level 27, and the penthouse space on level 47. Here are the substations that convert the power into usable and distributable levels, depending on which portion of the building the substation is serving. This originates with two 13.2 kV feeds from PECO that enter through the basement into the switchgear. These are then stepped down into 480Y/277V power in the basement level substations, where these feed not only basement level mechanical equipment, but also the emergency power circuit (powered by a 1500 kW diesel engine in the basment level) that runs the fire protection system, such as smoke detectors and emergency lights for the building.

 

The substations are then connected to bus duct risers that go up the mechanical shaft of the building. From this riser, the air handling units (labeled AHU-1 on the drawings) on each floor of the commercial space are connected with a fused disconnect switch, and two panels distributing power to the space’s lights, receptacles, the façade lighting, and other electrical uses are located roughly every four floors (one distributing 480Y/227V power and one distributing 208Y/120V power).

 

These bus duct risers are then connected to the five electrical substations located on the transfer floor mechanical room. Two of these substations, rated at 4000 Amps of current, are additional substations to help distribute the power for the commercial spaces, and one of the substations, rated at 3000 Amps, provide power for electrical services for half of the residential floors. Finally, the two additional substations (also rated at 4000 Amps) provide power and distribution service for much of the mechanical equipment within this space, such as the chillers, the chilled water pump for the chilled beam system that serves as the HVAC system for both the residential and commercial spaces, and the energy recovery units that help reduce the buildings total power and HVAC demands.

 

From the aforementioned 3000 Amp substation, a bus duct riser distributes power to the residential floors up to level 38 (a penthouse substation serves the remaining residential floors), connected by a 600 Amp, 3 phase fused disconnect switch (typical for all floors of the building). Two panels are located on every floor of the residential floor to serve the luxury apartments, one rated at 480Y/227V, and one rated at 208Y/120V, the latter which serves most of the receptacles, lighting, and other general electrical uses on each floor.

 

Finally, the penthouse mechanical space houses three electrical substations, one rated for 3000 Amps and two rated for 2500 Amps. The 3000 Amp substation serves as the substation for the residences on levels 38-46, and is set up in a similar fashion as the circuit for the lower residential floors. The two other substations power the emergency circuit that goes up the entire building via bus duct riser, as well as the rooftop mechanical equipment, such as the cooling towers and the make-up air units. These two substations, also provide power to two generators on the roof that are also part of the emergency circuit via 200 Amp fused disconnect switches and 480Y/277V transformers.

 

The difference in where the panels are located on each floor is attributed to the use of these floors. The apartment residences are going to want more centralization of electrical distribution, so if any work must be done on a particular circuit, a maintenance worker does not have to shut off multiple floors of power to safely do the work. The commercial space will consist of likely one company occupying multiple floors. It would be easier for maintenance personnel if all the electrical systems for one company were centralized in one location. Similar to the situation above in the residential space, one company would not like their operations to be slowed down or stopped as maintenance is performed on another company’s electrical service.