Wiring Diagrams 1: Graphical Symbols

"CL" is a ceiling-mounted luminaire (fixed directly to the ceiling). A chandelier is "CH" and a recessed luminaire is "DL". A pendant (hung from a cord or chain) has its own symbol rather than a letter.

"CH" is a chandelier (a decorative multi-lamp fixture hung from the ceiling). The examination center's sample questions also ask for a chandelier. A ceiling-mounted luminaire is "CL" and a recessed luminaire is "DL". A fluorescent lamp has its own symbol rather than a letter.

"DL" is a recessed luminaire (downlight) set into the ceiling. A ceiling-mounted luminaire is "CL" and a chandelier is "CH". A pendant has its own symbol rather than a letter.

A single-line diagram draws the two or three actual wires as one line, so the line shows the wiring route. One line is not necessarily one wire, and it is not fixed at two wires or three cores. The number of wires is worked out from the notes or a multi-line diagram.

"1.6" is a solid conductor diameter of 1.6 mm and "2C" means two cores (two wires inside the cable). 1.6 is not a cross-sectional area (areas are used for stranded wires such as 5.5). "C" counts cores, not cable runs. Length is not annotated.

Sizes such as 5.5, 8 and 14 are normally cross-sectional areas of stranded wire, so this is 5.5 mm². Solid wires such as 1.6 or 2.0 are given as diameters, but 5.5 is not a 5.5 mm solid wire. The number is not a count of wires or a length.

The R in VVR stands for round: a 600 V PVC-insulated PVC-sheathed round cable. The flat type is VVF, 600 V PVC-insulated wire is IV, and the cross-linked polyethylene cable is CV.

EM-EEF is a 600 V polyethylene-insulated, flame-retardant polyethylene-sheathed flat cable (EM = eco-material). The flat PVC cable is VVF, the round one is VVR, and the cross-linked polyethylene PVC-sheathed cable is CV.

"E" means threadless steel conduit, and 19 is its nominal size. Flexible synthetic-resin conduit is PF (or CD), rigid PVC conduit is VE, and Type 2 flexible metal conduit is F2.

PF is flexible synthetic-resin conduit (PF pipe). Threadless steel conduit is E, Type 2 flexible metal conduit is F2, and rigid PVC conduit is VE.

F2 is Type 2 flexible metal conduit. E19 is threadless steel conduit, VE16 is rigid PVC conduit, and CD16 is CD-type flexible synthetic-resin conduit.

The examination center says exam symbols follow JIS in principle: JIS C 0303:2000 for premises wiring symbols and the JIS C 0617 series for general electrical graphical symbols. So JIS C 0617 is the standard for general electrical symbols, not premises wiring symbols. JIS C 8303 covers plugs and socket-outlets and JIS C 3342 covers 600 V PVC-sheathed cables; they are product standards, not symbol standards.

Earth electrodes are annotated with the earthing class, EA to ED for Classes A to D, so ED is Class D. Class C is EC. An outlet with an earthing pole ("E") or earth terminal ("ET") is an annotation on the outlet symbol, not on an earth electrode.

"W" on a luminaire means wall-mounted. A floor-standing fixture is annotated "F". Rainproof is "WP"; "W" alone does not mean rainproof. Emergency lighting has its own symbol rather than an annotation.

"EX" means explosion-proof (for places where there is a risk of explosion). Rainproof is "WP", a built-in confirmation lamp is "L", and a delay switch is "D".

"H" on an outlet means medical use. With earthing pole is "E", the locking type is "LK", and the twist-lock (hook) type is "T". The same "H" means a built-in locator lamp on a switch and an HID lamp ballast on a small transformer, so read it according to the symbol it is attached to.

A pendant hangs from the ceiling by a cord, chain or similar. A fixture mounted directly on the ceiling is a ceiling luminaire (CL), one recessed into the ceiling is a recessed luminaire (DL), and one on the wall is wall-mounted (W).

Luminaire capacity is annotated as "watts × number of lamps", so "40W×2" is a fixture using two 40 W lamps. W is a unit of power, not current (A). The annotation does not count fixtures or lighting levels.

"P" gives the number of poles, so "2P" is a two-pole switch. A switch that controls one light from two places is a three-way switch, annotated "3". Current is written with A, so "2P" is not 2 A, and "2P" does not count gangs.

The annotation "3" on a switch means a three-way switch (controls one light from two places). Poles would be written with P, as in "2P". A bare "3" is not used for three gangs or for a 3 A rating.

The annotation "4" means a four-way switch, placed between two three-way switches so one light can be controlled from three or more places. It does not operate four lights separately, and it does not indicate time or current.

The annotation "H" on a switch means a built-in locator lamp, which glows when the switch is OFF so it can be found in the dark. A confirmation lamp that glows when ON is "L", and a passive-infrared automatic switch is "RAS". It does not mean a switch only for HID lamps.

A confirmation lamp glows when the switch is ON to show the load is operating; the built-in type is annotated "L". "H" is a built-in locator lamp that glows when OFF, "T" is with timer, and "P" is a pull switch.

The annotation "A" with the capacity (3A) is an automatic light switch used for outdoor lights, switching by ambient brightness. A passive-infrared automatic switch is "RAS", a delay switch is "D", and a remote-control switch is "R".

The annotation "D" is a delay switch: it actually turns off a set time after it is switched off (used for fans, for example). Turning on in the dark is the automatic light switch "A", sensing body heat is the passive-infrared switch "RAS", and a cord-operated switch is the pull switch "P".

A switch that senses infrared heat from the human body is the passive-infrared automatic switch, annotated "RAS". "A(3A)" is an automatic light switch that reacts to brightness, "D" is a delay switch, and "T" has a timer; none of them detects people.

For switches, a 15 A rating and single-pole type are not annotated, so a plain black dot is a single-pole 15 A switch. A three-way switch has "3", a two-pole switch has "2P", and ratings other than 15 A are written next to the symbol.

The annotation "E" on an outlet means it has an earthing pole (an earth contact in the socket). With earth terminal is "ET", with earth leakage breaker is "EL", and explosion-proof is "EX".

"EL" is an outlet with a built-in earth leakage breaker. With earthing pole and earth terminal is "EET", the locking type is "LK", and medical use is "H".

The locking (pull-out prevention) type is annotated "LK". "T" is the twist-lock hook type that uses a special plug, "ET" is with earth terminal, and "WP" is rainproof.

A general outlet rated 15 A, 125 V is not annotated. Ratings of 20 A or more (current), 250 V or more (voltage), and three or more poles are annotated.

A molded-case circuit breaker is "B", an earth leakage breaker is "E", and a switch (disconnector) is "S". The other sets mix up the letters. Do not confuse the "E" of an earth leakage breaker with the outlet annotation "E" (with earthing pole).

A bare number on an outlet gives the number of sockets, so "2" is a duplex outlet. Poles are written with P, such as "3P", and only for three or more poles. Current is written with A, as in "20A". It does not count appliances.

The mA value on an earth leakage breaker is the rated sensitivity current, the leakage current at which it operates. 20A is the rated current. Frame size is not given in mA, and a fuse rating is annotated on a switch (disconnector).

A molded-case circuit breaker is annotated with poles, frame size and rated current. Rated sensitivity current is a value for leakage detection, so it belongs on earth leakage breakers, not on molded-case circuit breakers.

"Wh" (watt-hour) is a unit of energy, so it is the watt-hour meter, which measures the energy used. A wattmeter measures instantaneous power (W), an ammeter measures current (A), and a voltmeter measures voltage (V).

Motors are annotated with the electrical system, voltage and capacity. "3φ" means three-phase, "200V" is the voltage and "0.75kW" is the capacity. "3φ" means three-phase, so it is not single-phase three-wire. kW is a unit of power, not current (A), and the annotation does not count motors.

"H" on a small transformer means a ballast for HID lamps. Medical use is the "H" on an outlet and a built-in locator lamp is the "H" on a switch; they are not small-transformer annotations. A bell transformer is "B".

"T" is a small transformer, and the annotation "B" means a bell transformer (for chimes and bells). A remote-control transformer is "R", a neon transformer is "N", and a fluorescent lamp ballast is "F".

For room air conditioners, the outdoor unit is annotated "O" and the indoor unit "I". "O" does not mean ceiling-mounted or rainproof (rainproof is WP).