Commercial Systems
In a 208Y/120-volt system, this is the nominal voltage from any phase to neutral.
What is 120 volts?
This part of a drawing explains the symbols used on the plan.
What is the legend?
Compared with a solid conductor, this conductor construction uses multiple smaller wires twisted together.
What is stranded conductor?
This lighting-control device detects occupancy to turn lights on or off.
What is an occupancy sensor?
A straight conduit route is 60 feet long. Ignoring cuts and waste, this many 10-foot sticks are required.
What is 6 sticks?
In a 480Y/277-volt system, this is the nominal voltage between two phases.
What is 480 volts?
This drawing shows a simplified power-distribution path using one line to represent multiple conductors.
What is a one-line diagram?
In American Wire Gauge sizes, changing from 12 AWG to 10 AWG makes the conductor this relative size.
What is larger?
This component supplies controlled electrical power to an LED light source.
What is an LED driver?
Eight luminaires each draw 0.5 ampere at their rated voltage. This is their combined current on the same circuit.
What is 4 amperes?
This distribution circuit supplies a panelboard rather than directly supplying the final utilization outlets.
What is a feeder?
This panel document identifies circuit numbers and the loads assigned to them.
What is a panel schedule?
On a dual-marked THHN/THWN-2 conductor, this part of the marking identifies suitability for wet locations at 90 degrees C.
What is THWN-2? (Termination limits and other ampacity rules still apply.)
A three-way lighting circuit normally uses two conductors between the switches for alternate current paths. These conductors have this name.
What are travelers?
A 2,400-VA single-phase load is supplied at 120 volts. This is its current.
What is 20 amperes?
Three equal line-to-neutral loads are placed one on each phase of an ideal wye system. Their fundamental-frequency neutral currents combine to this value.
What is zero amperes? (For balanced linear loads.)
A plan scale is 1/4 inch = 1 foot. A straight run measures 3 inches on the print. This is its actual length.
What is 12 feet?
A cable jacket says 12/2 WITH GROUND. This is the number of insulated circuit conductors, excluding the equipment grounding conductor.
What is two?
A 120-volt-only LED driver is proposed for a 277-volt lighting branch circuit. This equipment characteristic must match before connection.
What is the driver's input-voltage rating?
A 75-kVA three-phase transformer has a 208-volt secondary. This is its full-load secondary line current, rounded to the nearest ampere.
What is 208 amperes? (75,000 / (1.732 x 208).)
A balanced three-phase load draws 10 amperes at 208 volts line-to-line. This is its apparent power, rounded to the nearest 10 VA.
What is about 3,600 VA? (Square root of 3 x 208 x 10.)
A conduit route on the electrical plan conflicts with structural steel. Before changing the engineered route, submit this formal request for clarification.
What is a request for information (RFI)?
An installer proposes pulling more conductors because they physically fit. In addition to ampacity, these two installation limits must be checked to avoid pulling damage.
What are allowable pulling tension and minimum bend radius?
A dimmer and an LED driver both fit the box, but the lights flicker at low output. Before replacement, verify this relationship between the two devices.
What is compatibility of the dimming method and the dimmer/driver combination?
A balanced 480-volt three-phase load draws 20 amperes at 0.80 power factor. This is its real input power, rounded to the nearest tenth of a kilowatt.
What is 13.3 kW? (1.732 x 480 x 20 x 0.80 / 1,000.)