Commercial Power Distribution in the Denver Metro
Feeders, panelboards, and dry-type transformers sized and installed for the load they will actually carry.
Distribution is arithmetic before it is installation. Feeders are sized for continuous load, then adjusted for ambient temperature, conduit fill, and the length of the run, because voltage drop over a long pull is what leaves equipment at the far end running hot and behaving strangely. Panelboard locations follow the loads they serve and the working clearance required in front of them, not whichever closet happens to be left over.
Most commercial buildings distribute at 277/480 and step down where they need 120/208 for receptacles and smaller equipment. Dry-type transformers need correct secondary protection, proper grounding and bonding as a separately derived system, ventilation clearance, and consideration of harmonic-heavy loads that a standard unit is not built to feed. Everything downstream has to be rated for the fault current available at that point, and gear gets labeled so the next person knows what they are opening.
How is a commercial feeder sized?
Start with the calculated load, add the continuous load factor, then adjust conductor ampacity for ambient temperature and the number of current-carrying conductors in the raceway. Long runs get checked for voltage drop, and the conductor, the raceway, and the overcurrent device all have to agree with the equipment rating at both ends.
Why do commercial buildings have transformers inside them?
Because power is distributed at 277/480 to move it efficiently and feed lighting and motors, while receptacles and small equipment need 120/208. A dry-type transformer steps it down locally so the 120 volt distribution runs short and the big feeders stay small for the power they carry.
How much clear space is required in front of an electrical panel?
For the voltages in most commercial buildings, roughly three feet of depth, thirty inches of width or the width of the equipment, and six and a half feet of headroom, kept clear at all times. Storage stacked in front of gear is one of the corrections inspectors write most often.
Based in Golden and on site across the Denver metro, from Lakewood, Wheat Ridge, and Arvada to the foothills.