1. PURPOSE – This engineering article is about Instrument/Electrical Control Panel Internal Wiring Colour Requirement in plants based on BS 7671 British Standards.
2. Instrument/Electrical Control Panel Internal Wiring Colour Requirement
- This article applies to all control panels, switching panels, and interfacing panels designed by Company..
- This standard does not necessarily apply to panels/control boxes purchased as part of a standard package supplied by others.
- If applicable, this standard shall be overriden by local or national code requirements.
3. RELATED DOCUMENTS
3.1 British Standards Institute (BSI)
BS 7671 Requirements for electrical installations. IEE Wiring Regulations, Section 514, Tables 51A and 51B.
4. DEFINITION
4.1 Power Supplies 380V and above are high voltage, 3 phase, supply wiring for motor switchgear.
4.2 Power Supplies 240 VAC are the following:
- Internal distribution of 240 VAC power from panel isolator to panel circuit breakers (MCB).
- From MCB to each individual item of panel mounted equipment requiring 240 VAC supply.
- From isolator to 240V/110V ac step down transformer.
4.3 Power Supplies 110 VAC are the following:
- Internal distribution of 110 VAC power from panel isolator to panel circuit breakers (MCB).
- From MCB to each individual item of panel mounted equipment or circuit requiring 110 VAC supply.
4.4 Power Supplies 24 Vdc are the following:
- Internal distribution of 24 Vdc power from panel mounted 24 Vdc power supply unit to panel circuit breakers (MCB) or fused distribution system.
- From distribution system to each individual item of panel mounted equipment or circuit requiring 24 Vdc supply.
4.5 Control Signal 110 VAC is internal panel logic/digital circuits rated at 110 VAC.
4.6 Control Signal 24 Vdc is internal panel logic/digital circuits rated at 24 Vdc.
4.7 4-20 mA Signal is internal panel, analogue control, circuit rated at 4-20 mA (or 1-5 V).
4.8 Instrument Earth is isolated earthing of signals/cable screens to minimise interference in low current signal circuits.
4.9 Safety Earth refers to personnel and equipment protection to prevent exposure to voltage levels liable to cause injury or damage.
4.10 For further information, refer to BS7671.
COLOUR REQUIREMENTS
| • Power Supplies 380V and above | black, black, black, blue, green/yellow |
| • Power Supplies 240 VAC | brown (L)/Blue (N) |
| • Power Supplies 110 VAC | white (L)/yellow (N) |
| • Power Supplies 24 Vdc | red (+)/black (-) |
| • Control Signal 110 VAC | white |
| • Control Signal 24 Vdc | grey |
| • 4-20 mA Signal | black (+)/white (-) (pair cable screened) |
| • Instrument Earth (isolated) | green |
| • Safety Earth | green/yellow |
Instrument and Electrical Control Panels and Equipment