Much like human comfort, electrical engineering comes with its own unique language. At its core, electricity flows much like water in a hydraulic system, governed by three fundamental factors: potential/force, current, and resistance. Electrical force (V) is measured in volts, current (I) in Amps, and resistance (R) in Ohms.
Below are the questions I prepared myself before speaking with electrical engineers.
How is electricity transmitted and powered?
Direct Current (DC) means current flows in one direction at a constant voltage.
Alternating Current (AC) is based on the concept that electricity has nearly no inertia, and the direction of the flow can be reversed rapidly by reversing voltage. AC voltage can easily be stepped up to very high voltage for long-distance transmission (reducing line losses as V=IxR and P= IxV ) and stepped down safely within the building.
How is electricity used?
Generator: it is a device that converts mechanical energy into electrical energy.
Transformer: it is a device that uses different numbers of coils to step up or step down the voltage.
Wiring: The sizes of electrical wiring are standardized using American Wire Gage (AWG); the number goes from #14 up to #4/0(0000). #14 is considered the smallest allowed for standard residential branch circuits, and 0000 is the largest. (wires larger than #4/0 switch to kcmil(MCM) sizing.)
Voltage Setting:
Residential buildings usually receive 120/240V single-phase.
Small to medium commercial buildings usually receive 120/208V three-phase
Large commercial buildings require higher voltage, such as 277/480V three-phase.
Capacitor: it is a set of two plates separated by a small insulating layer. Currently, it is stored on one plate
Receptacle: it is also known as an outlet or wall plug, used to connect appliances to the circuit.
Electric feeder: it is a device that carries power from the main service to the subpanel
How to use different loads to design electrical equipment?
Resistive Load: such as toaster oven, incandescent light bulb. Increasing the cross-sectional area is a way to reduce resistance. Larger conductor directly mitigates voltage drop across long distances
Inductive Load: refrigerator, air conditioner, washing machine are this type of load.
Capacitive Load: devices such as capacitor banks to stabilize the power system
How to make sure we use electricity safely?
GFCI-Detects small current imbalance (4amp to 6 amp) between hot and neutral wire to prevent human electrocution
AFCI- it detects unintended electrical arcing conditions in circuit wiring to prevent electrical fire. (Electrical arcing is the luminous, high-temperature discharge of electric current that jumps across an insulating gap, such as air, between two conductors)
Load Control: Itl is normally installed directly next to the main electrical circuit breaker panel or inside a dedicated electrical utility room. They are integrated into this locations such as main electrical panel, utility room, junction box.
Safety Measurement by Code
10-Second Rule
2024 IBC 2702.1.4 Load Transfer: Emergency power system shall automatically provide secondary power within 10 seconds after losing primary power. Standby power shall provide secondary power within 60 second after losing primary power. (This 10-sec rule is derived from NEC 700.12. NEC article 700 governs the design, installation, operation, and maintenance of legally required emergency systems.)
90-Minutes illumination
2024 IBC 1008.3.1 Means of Egress Illuminsation talks about the required duration for emergency power system shall be minimum 90 minutes, and shall consist of storage batteries, unit equipment or an on-site generator.
2024 IBC 2702.2.14 Means of Egress Illuminsation: Emergency power shall be capable of powering the required load for duration not less than 90 minutes.
2 hours Emergency and Standby Power
2024 IBC 2702.1.5 Load Duration: Emergency power system and standby power system shall be designed to provide the required power for minimum duration of 2 hours without being refueled and recharged.
Workspace Requirement
2024 IBC 1010.2.8.2. Door Gate and Turnstiles: Rooms containing electrical equipment rated 800 ampere or more shall NOT be provided with a latch or lock other than panic hardware or fire exit hardware.
2024 IRC 3405.1 Workspace and Clearance: fig. 3405.1. states a 30-inch by 36-inch working space is required in front of energized equipment and panel board.