Iran Nezam Electrical Supervision Exam flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Lumen method formula

N = (E × A) / (Φ × CU × LLF). E is target illuminance in lux, A is room area in square metres, Φ is lumens per luminaire, CU is coefficient of utilization, LLF is light loss factor.

Receptacle spacing rule

In dwelling habitable rooms, no point along the floor line may be more than 1.8 metres from a general-purpose receptacle; kitchen countertop outlets are spaced at intervals not exceeding 1.2 metres.

Continuous load factor

Continuous loads, operating three hours or more, are taken at 125 percent of nameplate current when sizing branch circuits, feeders, overcurrent devices, and panel busbars.

Voltage drop limits

Branch circuits are limited to 3 percent voltage drop and the total from service to load to 5 percent; motor starting drop at terminals is commonly limited to 15 percent.

Conduit fill percentages

Maximum conductor fill of conduit interior area is 53 percent for one conductor, 31 percent for two conductors, and 40 percent for three or more conductors, per standard fill tables.

Bundling derating factors

More than three current-carrying conductors in one raceway require derating: 80 percent for four to six, 70 percent for seven to nine, and 50 percent for ten to twenty conductors.

Conductor colour code

Phase conductors are brown, black, and grey for L1, L2, L3; neutral is blue; protective earth is green-yellow. A PEN conductor is green-yellow with blue marking at terminations.

Minimum dwelling conductor sizes

Typical minimum copper sizes are 1.5 square millimetres for lighting, 2.5 for general receptacles, and 4 for kitchen, laundry, and water-heater circuits, subject to local code amendments.

Breaker and cable coordination

The protective device rating must be at least the design current and no greater than the corrected cable ampacity; the tripping current must not exceed 1.45 times that ampacity.

Earth-fault loop impedance

Disconnection is verified by Zs ≤ U0 / Ia, where U0 is line-to-earth voltage and Ia is the current that trips the protective device within the required disconnection time.

RCD Type A versus B

Type AC responds only to sinusoidal alternating residual current; Type A also responds to pulsating direct current; Type B is required for smooth direct residual current from chargers and inverters.

TN-C-S earthing system

The supply neutral also serves as protective conductor (PEN) up to the origin of the installation, where it is split into separate neutral and protective earth conductors downstream.

Main equipotential bonding size

The main bonding conductor is at least half the cross-section of the largest protective conductor and not less than 6 square millimetres copper, or 10 where the supply requires it.

IEC 60364 scope

The IEC 60364 series sets requirements for protection against shock, thermal effects, overcurrent, earthing, conductor sizing, and verification of low-voltage electrical installations.

Iranian building code Part 13

Part 13 of the Iranian national building code governs electrical installations of buildings, adopts IEC 60364 principles, and requires licensed-engineer design and supervision above the small-installation threshold.

Completion verification tests

Before energizing, verify protective conductor continuity, insulation resistance, earth electrode resistance, RCD trip time and current, polarity, and earth-fault loop impedance, and record results.

Standards conflict resolution

Where documents conflict, the mandatory national code and utility regulations prevail, followed by referenced IEC standards, then manufacturer instructions; the more stringent safety requirement is applied.

Three-phase power formula

Real power equals the square root of three times line voltage times line current times power factor; rearrange to find current from known power, voltage, and power factor.

Copper resistivity values

Copper resistivity is about 0.0175 ohm square millimetre per metre at 20 degrees Celsius and about 0.0225 at 70 degrees, the value used for voltage-drop calculations.

Demand versus diversity factor

Demand factor is the ratio of maximum demand to connected load for one load group; diversity factor relates the sum of individual maximum demands to the installation's coincident maximum demand.

Transformer sizing rule

Transformer kilovolt-amperes equals total demand in kilowatts divided by power factor and loading limit, typically 0.8, with 20 to 25 percent spare capacity added for growth.

Hazardous area zones

Zone 0, 1, and 2 denote continuous, likely, and unlikely presence of explosive gas; Zone 20, 21, and 22 apply the same logic to combustible dust atmospheres.

Ex protection concepts

Ex d is flameproof enclosure, Ex e increased safety, Ex i intrinsic safety, Ex p pressurization, and Ex n non-sparking; temperature classes T1 to T6 limit surface temperature, T6 being 85 degrees.

Emergency lighting performance

Escape routes require at least 1 lux on the centreline and open areas 5 lux; 50 percent output within 5 seconds, full output within 60 seconds, and 90 minutes duration minimum.

Firestopping penetrations

Every cable penetration of a fire-rated wall or floor must use a listed firestop system with the same fire resistance as the element, including internal and external sealing of trays.

Fire alarm cable separation

Fire alarm and detection cables use fire-resistant types in dedicated conduit and are separated from power circuits by at least 300 millimetres or a grounded barrier.

Elevator supply requirements

A dedicated feeder supplies the lift machine room, with an isolator within sight of the controller, separate car lighting, and a two-way communication supply independent of normal power.

PV inverter breaker sizing

The PV inverter output circuit breaker is rated at least 1.25 times the inverter maximum output current, with a DC isolator at the array and an RCD type suited to the inverter topology.

Data cable separation

Communication and IT cables are routed at least 300 millimetres from power circuits or behind a grounded divider, with a bend radius of at least four times the cable diameter.

Supervisor statutory duty

The licensed supervisor certifies that executed work conforms to approved drawings, the building code, and the permit, filing stage reports that gate the occupancy certificate.

Report submission stages

Supervision reports are filed at defined stages, typically foundation, structure, and completion; withholding a report suspends further permits and blocks the occupancy certificate.

Contract document hierarchy

Order of precedence is agreement, conditions of contract, specification, drawings, and bill of quantities; for safety and code compliance the more stringent document prevails.