Standards reference.

For Worldwide: KKE Circuit is available across Global in English. Region: Global (INT).

Wire colour codes

IEC 60446 / IEC 60445 wire colours

Quick answer: IEC 60446 (now folded into IEC 60445) defines the wire colour conventions used across Europe and most of Asia. L1 is brown, L2 is black, L3 is grey, neutral is light blue, protective earth is green-yellow. Control circuit colours are recommended (red for AC control, dark blue for DC control) but not strictly mandated.

Conductor	Colour	Hex (approx.)	Two-letter code
L1 (Phase 1)	Brown	#7B3F00	BN
L2 (Phase 2)	Black	#000000	BK
L3 (Phase 3)	Grey	#808080	GY
Neutral (N)	Light blue	#3FA9F5	BU
Protective earth (PE)	Green-yellow stripe	#00A859 / #FFD700	GNYE
AC control	Red	#E03A3E	RD
DC positive control	Dark blue	#1F3A93	BU (dark)
DC negative control	White	#FFFFFF	WH

UL 508A / NFPA 79 wire colours

Quick answer: UL 508A (industrial control panels) and NFPA 79 (electrical machinery) prescribe black for AC ungrounded power conductors, white for the AC grounded conductor (neutral), green or green-yellow for ground, red for AC control, and blue for DC ungrounded control. The standard is North American.

Conductor	Colour	Hex
AC ungrounded power (L1, L2, L3)	Black	#000000
AC grounded conductor (Neutral)	White	#FFFFFF
Equipment ground	Green or Green-Yellow	#00A859
AC control (incl. AC from control transformer)	Red	#E03A3E
AC control derived from a separate source that remains energised when main disconnect is off	Yellow	#FFD700
DC ungrounded (control)	Blue	#1F3A93
DC grounded conductor	White with blue tracer	—
Interlock control circuit derived from a different power source	Yellow	#FFD700

CSA C22.2 wire colours

CSA generally aligns with NFPA 79 for industrial machinery. For dwelling/installation wiring, the Canadian Electrical Code (CSA C22.1) uses:

Conductor	Colour
L1	Red
L2	Black
L3	Blue
Neutral	White
Ground	Green or bare

AS/NZS 3000 wire colours

Quick answer: AS/NZS 3000 (the Australian/New Zealand wiring rules) historically used red/white/blue for active phases, black for neutral, and green-yellow for earth. Since the 2007 amendment, the harmonised IEC colour scheme is also accepted: brown/black/grey for actives, blue for neutral, green-yellow for earth. Both colour schemes are seen in service.

Conductor	Pre-2007 (AS)	Post-2007 (harmonised IEC)
Active 1	Red	Brown
Active 2	White	Black
Active 3	Blue	Grey
Neutral	Black	Blue
Earth	Green / Green-Yellow	Green-Yellow

NEMA wire colour conventions

NEMA does not publish a wire-colour standard separate from NFPA 79; in practice "NEMA" panels use the NFPA 79 colour scheme. KKE Circuit's NEMA standard option applies the same colour palette as UL 508A but uses NEMA-style reference designators.

IEC vs. UL wire colours — side-by-side

Conductor	IEC 60446	UL 508A / NFPA 79
Phase 1	Brown	Black
Phase 2	Black	Black
Phase 3	Grey	Black
Neutral	Light Blue	White
Earth / Ground	Green-Yellow	Green or Green-Yellow
AC control	Red (recommended)	Red (mandated)
DC control +	Dark Blue (recommended)	Blue (mandated)
DC control −	White (recommended)	White with blue tracer (mandated)
Foreign-source interlock	—	Yellow (mandated)

Phase, neutral, PE colour codes by region

Region	Standard	L1	L2	L3	N	PE
EU (harmonised)	IEC 60446	Brown	Black	Grey	Blue	Green-Yellow
UK (post-2004)	BS 7671	Brown	Black	Grey	Blue	Green-Yellow
UK (pre-2004 — legacy installs)	—	Red	Yellow	Blue	Black	Green-Yellow
USA	NFPA 79	Black	Black	Black	White	Green
Canada	CSA C22.1	Red	Black	Blue	White	Green or bare
Australia/NZ (post-2007)	AS/NZS 3000	Brown	Black	Grey	Blue	Green-Yellow
Australia/NZ (pre-2007 — legacy)	AS/NZS 3000	Red	White	Blue	Black	Green-Yellow
India (legacy)	IS 732	Red	Yellow	Blue	Black	Green
India (current — harmonised)	IS 732	Brown	Black	Grey	Blue	Green-Yellow

Reference designators

IEC 60617 reference designators — full table

Quick answer: IEC 60617 (and the broader IEC 81346) defines single-letter prefixes that classify a component on a drawing. K is a contactor or relay, Q is a switch or circuit breaker, F is protection (fuse, MCB), M is a motor, T is a transformer, X is a terminal. KKE Circuit auto-assigns these prefixes when you place a component on an IEC project.

Prefix	Meaning	Examples
A	Assembly, sub-assembly	Drive unit, PLC rack
B	Sensor, transducer	Photocell, RTD, thermocouple
C	Capacitor	Power factor cap
D	Diode, semiconductor	Diode, Zener
E	Miscellaneous	Heater, lamp
F	Protection	Fuse, MCB, surge arrester
G	Generator, supply	Generator, battery, PSU
H	Signalling	Pilot lamp, buzzer
K	Contactor, relay	Contactor, control relay, time relay
L	Inductor	Reactor, choke
M	Motor	AC motor, DC motor, servo
P	Indicator, measuring	Voltmeter, ammeter, hour-meter
Q	Switching device	MCCB, isolator, disconnect
R	Resistor	Heater resistor, braking resistor
S	Switch (control)	Push-button, selector switch
T	Transformer	Power transformer, control transformer
U	Modulator, converter	VFD, rectifier, inverter
V	Vacuum tube, semiconductor	Thyristor, IGBT
W	Transmission path	Cable, busbar, waveguide
X	Terminal, plug	Terminal block, connector
Y	Electrically operated mechanical device	Solenoid valve, brake
Z	Filter	EMC filter, line filter

UL 508A reference designators

Quick answer: UL 508A does not formally mandate reference designators, but North American industrial practice uses multi-letter prefixes that read as English abbreviations: CR for control relay, CB for circuit breaker, FU for fuse, MTR for motor, XFMR for transformer, TB for terminal block. KKE Circuit applies these prefixes when the project's electrical standard is UL 508A.

Prefix	Meaning	IEC equivalent
CR	Control Relay	K
CB	Circuit Breaker	Q
FU	Fuse	F
MTR	Motor	M
XFMR	Transformer	T
TB	Terminal Block	X
PB	Push Button	S
SS	Selector Switch	S
LT	Pilot Light	H
SOL	Solenoid	Y
PS	Power Supply	G
DR	Drive (VFD / servo)	U
DS	Disconnect Switch	Q
GFI	Ground Fault Interrupt	F
IS	Interposing relay	K

Reference designator best practices

• Keep the prefix consistent across the project — KKE Circuit enforces this when a standard is set.
• Numbers should increment without gaps within a panel; gaps appear after deletes — use Project → Renumber to compact.
• For multi-panel projects, prefix the panel: +CAB1-K1, +CAB2-K1 — KKE Circuit's panel manager handles the prefix automatically.
• Avoid letter+letter for the auxiliary number — K1A, K1B is hard to sort. Use K1.1, K1.2.

Symbol references

IEC 60617 symbol library

Categories covered:

• Switching devices: contactors, MCCBs, isolators, disconnectors, knife switches, MCB, RCD, RCBO
• Protection: fuses, surge arresters, overload relays, thermal trip
• Transformers: power, control, current, voltage, auto, isolating
• Motors: AC induction, AC sync, DC, servo, stepper
• Generators, batteries, UPSs, power supplies
• Indicators: pilot lamps, buzzers, voltmeters, ammeters
• Push-buttons: NO, NC, mushroom, illuminated, key-operated
• Selector switches: 2-pos, 3-pos, key
• Sensors: proximity, photoelectric, RTD, thermocouple, pressure, level
• Relays: control, time-delay, latching, safety
• Solenoids, brakes, clutches
• Terminals, plugs, connectors
• VFDs, drives, soft starters
• Capacitors, resistors, inductors
• Diodes, thyristors, IGBTs

NEMA ICS symbol library

NEMA ICS 19 defines a parallel set of symbols common in North American industrial drawings. KKE Circuit ships the NEMA variants as alternative geometries on the same library parts.

ISA-5.1 symbol library

Quick answer: ISA-5.1 is the American National Standard for instrumentation symbols. Every instrument is drawn as a circle (the bubble) with a tag inside (FT-101) and a line type that distinguishes panel-mounted, field-mounted, behind-panel, shared-display, computer-function and software-link instruments.

Bubble style	Meaning
Circle, no line	Field-mounted, single-function, locally accessible
Circle, single horizontal line	Panel-mounted, single-function, primary location
Circle, double horizontal line	Auxiliary panel, primary location
Circle, single dashed line	Behind panel (not normally accessible)
Hexagon	Computer function
Square with circle inside	DCS / shared display
Diamond	PLC function

Tag prefixes (first letter)

Letter	Measured/initiating variable	Letter	Modifier
F	Flow	I	Indicate
L	Level	T	Transmit
P	Pressure	C	Control
T	Temperature	R	Record
A	Analysis	S	Switch
H	Hand (manual)	E	Element (sensor)
Q	Quantity / total	V	Valve / final element

So FT-101 = Flow Transmitter, loop 101. LIC-205 = Level Indicating Controller, loop 205. PSH-310 = Pressure Switch High, loop 310.

ISO 1219 pneumatic & hydraulic symbol library

ISO 1219-1 (graphical symbols) and ISO 1219-2 (circuit diagrams). KKE Circuit's library covers:

• Pumps & compressors (fixed-displacement, variable-displacement)
• Reservoirs & receivers
• Filters & FRLs
• Directional control valves: 2/2, 3/2, 4/2, 4/3, 5/2, 5/3
• Check valves & pilot-operated check valves
• Flow controls (fixed, variable, pressure-compensated)
• Pressure controls (relief, reducing, sequence)
• Cylinders (single-acting, double-acting, telescopic)
• Hydraulic & pneumatic motors
• Accumulators
• Mufflers & silencers

ISO 10628 P&ID symbol library

ISO 10628-1 / -2 covers P&ID specifically — process equipment (pumps, compressors, vessels, heat exchangers, columns), pipe components (fittings, reducers, expanders), valves (gate, ball, butterfly, plug, globe, needle, diaphragm, check), and fluid handling.

ISA-5.1 line types

Line type	Visual	Purpose
Process pipe	Solid line	Main process flow
Pneumatic signal	Line with double slashes (//)	Pneumatic instrumentation signal
Electric signal	Dashed line	4-20 mA, 0-10 V, etc.
Hydraulic signal	Line with single slashes (/)	Hydraulic actuation signal
Capillary	Line with X marks	Sealed liquid connection (filled bulb thermometer)
Software / data link	Dashed line with circles	DCS / PLC / fieldbus link
Mechanical link	Line with circles or wave	Mechanical linkage (rotating shaft, lever)

In KKE Circuit, the line type is set on the line's property panel; the auto-colour rule still applies based on the connected pin's fluid kind.

P&ID fluid line colour conventions

Quick answer: Although ISA-5.1 does not mandate colour, industry practice (and many corporate engineering standards) colours process lines by their fluid: water blue, oil red, compressed air cyan, hydraulic oil dark red, steam orange, fuel gas yellow. KKE Circuit applies these conventions automatically based on the pin's fluid kind.

Fluid	KKE Circuit colour	Hex
Water	Blue	#1976D2
Oil	Red	#C62828
Compressed air	Cyan	#00ACC1
Hydraulic oil	Dark red	#8B1A1A
Steam	Orange	#F57C00
Fuel gas	Yellow	#FBC02D
Nitrogen / inert gas	Light grey	#9E9E9E
Wastewater	Dark blue	#0D47A1

Cable & engineering standards

IEC 60364-5-52 cable sizing

Quick answer: IEC 60364-5-52 is the international standard for low-voltage cable sizing. It specifies the current-carrying capacity (Iz) of cables based on their cross-section, conductor material (copper or aluminium), insulation type (PVC, XLPE, EPR), installation method (in conduit, on tray, buried, in air), ambient temperature, and number of grouped circuits. KKE Circuit's cable sizer is a direct implementation of the IEC 60364-5-52 tables and derating rules.

The sizing process:

1. Determine the design current (Ib) — the steady-state current the circuit must carry.
2. Pick a protective device rating (In) such that In ≥ Ib.
3. Apply derating factors: ambient temperature (Ca), grouping (Cg), thermal insulation (Ci), soil resistivity (for buried).
4. Compute the required cable Iz = In / (Ca × Cg × Ci).
5. From IEC 60364-5-52 tables, pick the smallest cross-section whose tabulated Iz at the chosen installation method exceeds the required Iz.
6. Voltage drop check: confirm voltage drop is below 4% (lighting) or 5% (power) over the cable run length. If it fails, increase the cross-section.

Cable installation methods

Method	Description	Typical use
A1	Insulated conductors in conduit in a thermally insulated wall	Domestic concealed wiring
A2	Multi-core cable in conduit in a thermally insulated wall	Domestic concealed wiring
B1	Insulated conductors in conduit on a wooden wall	Surface conduit
B2	Multi-core cable in conduit on a wooden wall	Surface conduit
C	Single- or multi-core cable clipped direct to a non-metallic surface	Surface clipping
D1	Multi-core cables in ducts in the ground	Underground ducts
D2	Multi-core cables direct in the ground	Direct burial
E	Multi-core cable in free air	Tray, ladder, brackets
F	Single-core cables in free air, touching	Tray, ladder, brackets
G	Single-core cables in free air, spaced	Tray, ladder, brackets

Ambient temperature derating factors

Ambient (°C)	PVC Ca	XLPE Ca
25	1.06	1.04
30	1.00	1.00
35	0.94	0.96
40	0.87	0.91
45	0.79	0.87
50	0.71	0.82
55	0.61	0.76

Cable grouping derating factors

Number of circuits	Cg (touching)
1	1.00
2	0.80
3	0.70
4	0.65
5	0.60
6	0.57
9	0.50

Voltage drop calculation

Voltage drop on an AC circuit is approximated as:

Vdrop = (√3 × I × L × (R cosφ + X sinφ)) / 1000      (three-phase)
Vdrop = (2   × I × L × (R cosφ + X sinφ)) / 1000      (single-phase)

where I is current in amps, L is one-way length in metres, R and X are resistance and reactance per kilometre at operating temperature, cosφ is the load power factor.

KKE Circuit pulls R and X from its cable database and applies the formula automatically.

Copper PVC vs. XLPE cable selection

Property	PVC	XLPE
Max conductor temperature	70 °C	90 °C
Current-carrying capacity	Lower	~30% higher
Cost	Lower	Higher
Halogen content	Yes	No (LSZH variants available)
Common use	Indoor, domestic, light industrial	Industrial, motor circuits, MV