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For example, a 480Y/277V, three-phase, 4-wire switchboard will be installed in an electrical room. This clearance is different if the 480-volt electrical panel faces a wall where other electrical panels are located.

The most common commercial construction electrical service in North America is 120/208 volts in star, which is used to power 120 volt outlet loads, lighting and smaller HVAC systems.

Because the drywall is not considered grounded, Condition 1 applies. Where all exposed live parts operate at not greater than 30V rms, 42V peak or 60V direct current (DC), smaller working space shall be permitted but only by special permission. However, because this is an existing building, the minimum clear distance in front of the switchboard can be 3 feet, 6 inches as long as written procedures have been adopted to prohibit equipment on both sides of the aisle from being open at the same time. If exposed live parts are on both sides of the working space but are effectively guarded by insulating materials, this first condition would also apply. A minimum of 30 inches of width is also required in front of the electrical panel.

Can anyone help? This clearance is measured for the live electrical parts or front of the electrical panel. In a new installation, the minimum clear distance in front of the 480V switchboard is 4 feet. 3 phase machinery runs off Delta voltage, which means you only run 3 hot wires and no neutral wire. So to determine the voltage to ground, for the purposes of finding your way around that table, you do not take the value of 11,600 and divide by 1.732, and you do not take the value of 12,500 and divide by 1.732. From contributor B: This clearance is different if the 480-volt electrical panel faces a wall where other electrical panels are located. These requirements are necessary to keep maintenance personnel safe while working on high-voltage panels.

Construction and Design Requirements.

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In accordance with 110.26(A)(1)(c), if this is an existing building where dead-front switchboards, switchgear, panelboards or motor control centers are being replaced and are across the aisle from exposed live parts, it may be permissible to use the distance specified under ­Condition 2 instead of Condition 3.