Earthing tags are an important part of any electrical installation or equipment. They provide a vital safety function by connecting exposed metalwork and structures to the main earth terminal. This ensures that any electrical fault currents are safely directed to earth rather than posing a risk of electric shock to users. Here we’ll look at what exactly earthing tags are, why they are needed, and how to correctly install and use them.
What Are Earthing Tags?
Earthing tags, also known as earth tags or earth straps, are simple fitting devices designed to provide an earthing connection point on electrical equipment and metal structures. They consist of a lug made from electroplated copper which is securely crimped or brazed to a braided earthing conductor cable.
The cable will then be connected to the main earth terminal or bar to safely earth the attached equipment or structure. Earthing tags are commonly made from copper or copper alloy and are available in a wide range of sizes to suit different cable conductors and applications.
The lug portion of the tag is normally fitted with a hole used to bolt directly to any conductive surface which requires earthing. This provides a solid and secure electrical connection. The braided cable tail can then be safely routed and terminated at the desired earth bonding point.
Why Are Earthing Tags Needed?
Earthing tags serve a critical electrical safety purpose. By bonding all exposed conductive surfaces to the main earth terminal, any stray currents due to electrical faults or transient voltages will be safely directed to ground. This equalises the potential of the surfaces to earth and prevents the risk of electric shock.
Some key reasons why earthing tags are essential include:
- Electric shock protection – Earthing provides protection from shock by directing fault currents away from personnel. Touching live equipment can be fatal without earthing.
- Surge protection – Earthing helps dissipate potentially damaging voltage surges due to lightning strikes or grid spikes. This protects sensitive electronics from damage.
- Electromagnetic compatibility – Earthing tags prevent interference by maintaining equipment, cabinets and structures at the same ground potential. This avoids issues with EMI/RFI.
- Static electricity – Bonding items to ground avoids build up of static charges which could discharge as sparks and damage electronics or be a fire hazard.
Earthing alone does not provide full electrical safety. It works in conjunction with other measures like insulation and residual current devices (RCDs) to minimise all round risk. However, earthing remains a fundamental requirement of any safe electrical installation.
Where Are Earthing Tags Used?
Earthing tags have a very wide range of applications across electrical and industrial settings. Some common examples include:
- Bonding metal panels, machine casings and cabinets to ground.
- Providing earthing points on switchboard enclosure frameworks.
- Earthing cable trays, ducts, trunking and baskets holding power cables.
- Grounding telecoms and data equipment frameworks and racks.
- Earthing metal roofs, mast structures and lightning conductors.
- Bonding metal water and gas pipework to ground potential.
- Grounding antennas, aerials, masts and satellite dishes.
- Earthing armoured cables and cable glands.
- Grounding metal air conditioning ducts and ventilation systems.
- Providing bonding points on generator frames and fuel tanks.
So in summary, earthing tags can be applied anywhere a conductive surface or structure needs to be securely bonded to the main earth for safety reasons. Their versatility makes them a common component in many electrical installations.
Earthing Tag Conductor Size
Earthing tags are available in a range of conductor sizes to suit different applications and grounding cable current-carrying capacities. The larger the conductor size, the more current it can safely carry to earth in a fault condition.
Common sizes include:
- 16mm2 conductor – Can carry around 470A under fault conditions. Use for major item grounding like switchboards.
- 10mm2 conductor – Can carry approximately 300A under fault conditions. Used for distribution boards, machine tools etc.
- 6mm2 conductor – Can carry approximately 185A under fault conditions. Used for general earthing applications.
- 4mm2 conductor – Can carry approximately 115A under fault conditions. Used for smaller installations and equipment.
The size used will depend on the prospective earth fault current ratings determined during the installation design stage. It’s important to select a tag rated for the potential maximum fault current to ensure safety and prevent damage.
Using undersized earthing tag conductors could result in the cable overheating and failing in a major fault scenario. Always check relevant standards and regulations when sizing earthing system components.
Earthing Tag Regulations
Installation and sizing of earthing tags must comply with the relevant safety standards and wiring regulations. In the UK, key guidelines include:
- BS 7671 – UK Wiring Regulations – Mandates earthing system design, earth conductor sizing and bonding requirements.
- BS 7430 – Earthing Standards – Best practice standard for all aspects of electrical earthing installations.
- BS EN 50522 – Earthing Bonding Standards – Specifies requirements for protective conductors, earth electrodes and bonds.
Other applicable standards include those relating to specific environments like construction sites, railways, healthcare premises etc. Always check you are adhering to the latest release of all relevant standards for the installation.
While regulations set the overall standard, the specifics of installation can vary. Consult an electrical inspector or qualified electrician if in any doubt about suitable earthing methods.
How To Install Earthing Tags
Installing earthing tags correctly is vital for safety. Follow these key steps when fitting earthing tags:
1. Determine The Required Location(s)
Decide where earthing points need to be established on the equipment or structure. Spread multiple tags at suitable intervals if bonding a long section like ducting or cable tray.
2. Clean The Contact Surface
Thoroughly clean the mounting point area using a wire brush and solvent to remove any paint, grease and dirt. This ensures good electrical contact with the metalwork.
3. Drill And Tap Mounting Hole
For bolt fixing, drill and tap an appropriately sized clearance hole in the equipment panel or structural section.
4. Securely Attach The Earthing Tag
Bolt the tag lug firmly to the prepared mounting point. Use spring washers or lock nuts to maintain tightness against vibration.
5. Route The Conductor To Earth Terminal
Run the earthing conductor back to the main earth bar or terminal, cutting it to length as required. Avoid routing near hazards where possible.
6. Make Off The Conductor Connection
Remove insulation then secure the conductor firmly under an earth bar bolt, clamp or terminal block. Use cable lugs for larger conductors.
7. Test Earthing Continuity
Check earth loop impedance and carry out continuity testing to verify correct installation and low resistance.
Following good practice will ensure the tag installation provides reliable and safe earthing for the life of the electrical system. Testing and regular inspection is key.
Earthing Accessories
There are various accessories available to enhance earthing tag installation and improve electrical safety. These include:
- Insulated earthing tags – Provide protection against accidental contact with live terminals and energised equipment.
- Double earthing tags – Allow two conductors to be terminated at one point for better continuity.
- Flexible earthing braids – Maintain earthing during movement and vibration on equipment couplings or doors.
- High temperature tags – Withstand heat exposure where standard PVC insulated tags may fail.
- Armoured earthing straps – Provide mechanical protection against physical damage in harsh environments.
- Stainless steel tags – For use in corrosive areas like chemical plants to avoid deterioration.
Using appropriate accessories suited to the operating environment will extend the working life of the earthing installation and enhance overall resilience.
Earthing Tag Maintenance
While earthing tags are inherently robust, maintaining them properly ensures they continue to provide effective, low-resistance grounding protection:
- Carry out regular visual inspections to check for mechanical damage, corrosion and loose connections.
- Periodically use a low-resistance ohmmeter to measure earth loop impedance back to the main earthing terminal.
- Check earthing conductors for integrity and reconnect or replace damaged cables.
- Re-tighten loose tag fixings firmly to maintain a solid connection with the earthed item.
- Remove any accumulated dirt, grime and surface corrosion on tags to keep contact resistance low.
- Apply antioxidant grease or gel to earthing tag contact points if situated in damp conditions prone to oxidation.
Proper maintenance and testing extends the service life of tags and keeps the critical earthing system operating reliably and safely.
Summary
Installing good quality earthing tags allows exposed conductive equipment, structures and components to be securely bonded to the main earth terminal. This equalises the surface potential to earth and directs damaging fault currents safely away from personnel and sensitive electronics.
Earthing tags provide a simple termination point to connect essential protective grounding conductors. Following proper installation practices, testing and maintenance procedures ensures these tags continue to deliver effective electrical shock and fire protection for the service life of the system.
Checking applicable wiring regulations and earthing standards is vital to guide correct specification and sizing. With competent design and skilled fitting, earthing tags form a simple yet invaluable part of any electrical safety system.