Wide multi-hole bar
About 100 mm wide and 600 – 800 mm long with roughly 30 – 36 holes in two or three rows. Used as a main earth bar in plant rooms, communication rooms and large distribution boards.
Grounding and bonding
Aluminium Ground Bus Bar: Earth Bar Material Guide
A ground (earth) bus bar is the common connection point that ties equipment, cabinet and structural bonding conductors to the earthing system. Aluminium ground bars in 1060, 1350 or 6101 carry fault current at about half the weight and a fraction of the metal cost of copper, provided the cross-section is increased and joints are made correctly. Metline supplies the aluminium bar cut to length, drilled to your hole pattern and plated where needed.
- Alloys
- 1060 · 1350 · 6101 · 6063
- Conductivity
- About 55 – 62 % IACS
- Common sizes
- 25 – 100 mm wide, 6 – 10 mm thick
- Finish
- Bare or tin-plated
What a ground bus bar does
Unlike a phase or neutral busbar, a ground bar carries no current in normal service. Its job is to provide a low-impedance path during a fault, so that protective devices trip quickly, and to hold every bonded metal part at the same potential so nobody can be exposed to a dangerous touch voltage.
In a distribution board or control cabinet, the ground bar collects the protective (PE) conductors of each outgoing circuit and connects them to the main earthing terminal. In a substation or plant room, larger earth bars link switchgear frames, cable armour, transformer tanks and the earth electrode system. In telecom and data rooms, bonding busbars collect the bonding conductors from racks, cable trays and surge protection.
Because a ground bar must survive the full prospective fault current for the clearing time of the protective device, it is sized by short-circuit withstand rather than continuous ampacity. That is the key difference when you design it in aluminium.
| Bar | Normal current | Purpose |
|---|---|---|
| Phase busbar | Carries load current | Distributes power to outgoing circuits |
| Neutral busbar | Carries unbalanced and harmonic current | Return path for single-phase loads |
| Ground / earth bus bar | None in normal service | Fault-current path and equipotential bonding |
Aluminium or copper for a ground bar?
Copper and tinned copper are the traditional choice, and many telecom specifications call for them. Aluminium is widely used for earth bars in power distribution, switchgear, industrial plants and large installations where weight and cost matter, and where the governing specification permits it.
| Property | Aluminium 1350 / 1060 | Aluminium 6101-T6 | Copper (C11000, for comparison) |
|---|---|---|---|
| Conductivity (typical) | About 61 – 62 % IACS | About 55 – 57 % IACS | About 100 % IACS |
| Density | 2.70 g/cm³ | 2.70 g/cm³ | 8.89 g/cm³ |
| Cross-section for equal resistance | About 1.6 × copper | About 1.8 × copper | 1.0 |
| Weight for equal resistance | About 50 % of copper | About 55 % of copper | 100 % |
| Mechanical strength | Low (soft temper) | Good; self-supporting long bars | Moderate |
| Oxide film | Hard, insulating; joints need preparation | As 1350 | Conductive oxide; easier joints |
In practice: choose aluminium for large earth bars, switchgear earth runs and long horizontal bars where weight, cost and stiffness count; choose a tin-plated aluminium bar where many copper lugs are bolted on; and follow the specification where it names copper explicitly. Metline supplies aluminium only, so when copper is mandatory we can help with the aluminium parts of the system, such as the main busbars or copper-clad aluminium bar where it is accepted.
Sizing an aluminium ground bar
Protective conductors are sized with the adiabatic equation used in IEC 60364-5-54 and similar codes: S = I√t / k, where S is the cross-section in mm², I the fault current in amperes, t the disconnection time in seconds, and k a factor that depends on the conductor material and its permitted temperature rise. For aluminium, k is roughly two-thirds of the copper value (for example 95 against 143 for PVC-insulated separate conductors in the IEC table), so the aluminium section must be about 1.5 times larger for the same fault duty.
- Find the fault levelTake the prospective earth-fault current at the board and the clearing time of the upstream device.
- Apply the adiabatic checkCalculate the minimum section with the aluminium k factor for the insulation and installation conditions in your code.
- Allow for holesSubtract the section lost to drilled holes at the narrowest point; this is often what governs a heavily drilled bar.
- Check mechanical needsBars over about 600 mm long, or carrying many heavy cables, benefit from 6101-T6 or a thicker section to stay rigid.
- Confirm the lugsMake sure the bar width and hole spacing suit the lug sizes, with room for a socket around each nut.
The table gives section, weight and the approximate copper section of equal resistance for common bar sizes in 1350 or 1060. Weights are calculated from 2.70 g/cm³ before drilling.
| Bar size (mm) | Section (mm²) | Weight (kg/m) | Equivalent copper section (mm², approx.) |
|---|---|---|---|
| 25 × 6 | 150 | 0.41 | 94 |
| 40 × 6 | 240 | 0.65 | 150 |
| 50 × 6 | 300 | 0.81 | 188 |
| 50 × 10 | 500 | 1.35 | 312 |
| 75 × 10 | 750 | 2.03 | 469 |
| 100 × 6 | 600 | 1.62 | 375 |
| 100 × 10 | 1000 | 2.70 | 625 |
Equivalent copper section uses a 1.6 conductivity ratio for 1350/1060. For 6101-T6, use about 1.8. Always confirm the final size with the fault calculation for your installation.
Typical ground bar sizes and hole layouts
Cabinet bar
About 50 – 75 mm wide and 400 – 600 mm long, 20 – 30 holes. Fits distribution and control cabinets with flexible wiring.
Narrow space-saving bar
About 25 – 40 mm wide and 300 – 500 mm long, 12 – 24 holes. For compact enclosures and mounting rails.
Short equipment bar
About 50 mm wide and 200 – 300 mm long, 8 – 16 holes. Short bonding points between equipment and the cabinet earth.
Terminal-style bar
Narrow bar with tapped holes and clamping screws for many small PE conductors in a row.
Long horizontal earth run
Straight lengths up to several metres along switchgear line-ups, usually 6101-T6 for stiffness, jointed with bolted splice plates.
Hole patterns usually follow the two-hole lug spacing of the conductors being connected (for example 5/8 in or 1 in centres for North American two-hole lugs, or metric spacings for DIN lugs). Send a sketch with hole diameter, pitch and edge distances and we cut and drill to it.
Making reliable joints on aluminium ground bars
Almost every problem with aluminium grounding comes from poor joints, not from the bar itself. Aluminium forms a hard insulating oxide within minutes of exposure, it creeps under sustained bolt load, and it corrodes galvanically when wet and in contact with copper. Each of these is solved by good practice:
- Surface preparation: wire-brush or abrade contact areas and apply an oxide-inhibiting joint compound immediately, before bolting
- Plating: tin-plated aluminium contact faces give stable, low resistance against copper lugs; see tin-plated aluminium bus bar
- Bimetal transitions: where copper and bare aluminium meet outdoors or in damp rooms, use bimetallic washers or Al-Cu transition pieces
- Spring washers: Belleville (conical) washers maintain clamping force as aluminium relaxes and through thermal cycles
- Rated hardware: lugs and connectors marked for aluminium (AL or AL/CU) and torqued to the manufacturer value
- Inspection: periodic torque checks or thermography on large earth bars in critical installations
Mill-finish aluminium is fine for dry indoor cabinets where joints are prepared properly. Tin plating is the usual upgrade for many-lug bars and humid locations. Anodising is not used on contact areas because the anodic film insulates.
Standards that apply to ground bars
| Standard | What it covers | Point to note for aluminium |
|---|---|---|
| IEC 60364-5-54 | Earthing arrangements and protective conductors | Gives the k factors and minimum sections for aluminium protective conductors |
| NFPA 70 (NEC) Article 250 | Grounding and bonding in North America | Restricts bare aluminium grounding conductors in contact with masonry or earth, and near earth outdoors |
| IEEE Std 80 | Safety in AC substation grounding | Conductor sizing and fusing temperatures for substation grounding materials |
| ANSI/TIA-607 series | Telecom bonding and grounding (PBB and SBB, formerly TMGB and TGB) | Busbars are normally specified in copper; confirm before choosing aluminium |
| ASTM B236 / B317 | Aluminium bar for electrical purposes (1350 and 6101) | Material specification for conductivity, temper and dimensions |
| IEC 61439 | Low-voltage switchgear and controlgear assemblies | Short-circuit withstand of the protective circuit in the assembly |
Local wiring rules override general guidance. Have a qualified engineer confirm material, size and installation method for your project.
Where aluminium ground bars are used
Distribution boards and MCCs
Earth bars along the base or rear of panels, collecting the PE conductors of every outgoing feeder.
Switchgear and substations
Continuous earth bars along switchgear line-ups and bonding bars for transformers and cable sealing ends.
Industrial plants
Main earth bars in plant rooms, bonding bars for process equipment, cable trays and structural steel.
Renewable energy
Earth bars in solar combiner boxes, inverter stations and battery containers, where aluminium cabling is already common.
Data and communication rooms
Equipotential bonding of racks and trays where the project specification permits aluminium.
Buildings
Main earthing terminals and equipotential bonding bars in plant rooms, where accepted by local rules.
References and standards
- IEC 60364-5-54 – Low-voltage electrical installations: Earthing arrangements and protective conductors
- NFPA 70 – National Electrical Code, Article 250 Grounding and Bonding
- IEEE Std 80 – Guide for Safety in AC Substation Grounding
- ANSI/TIA-607 – Generic Telecommunications Bonding and Grounding (Earthing) for Customer Premises
- ASTM B317/B317M – Aluminum-Alloy Extruded Bar, Rod, Pipe and Structural Shapes for Electrical Purposes (Bus Conductor)
Aluminium ground bus bar: frequently asked questions
What is the difference between a ground bus bar and a neutral bus bar?
A neutral bar carries return current from loads in normal operation. A ground bar carries current only during a fault and bonds metal parts to earth. They are connected together only at the point required by the earthing system, typically the main service or source.
Should a ground bus bar be copper or aluminum?
Both work. Copper is more compact and is often mandated in telecom specifications. Aluminium is lighter and cheaper for the same fault capacity but needs about 1.5 – 1.6 times the cross-section and properly prepared joints. Follow your project specification and local code.
Which aluminium alloy is best for an earth bar?
1350 or 1060 give the highest conductivity and are ideal for short, well-supported bars. 6101-T6 is slightly less conductive but much stiffer, which suits long or self-supporting bars. 6063 is used where the bar is part of an extruded profile.
Can you drill the holes to our layout?
Yes. We cut aluminium bar to length and drill or tap holes to your drawing, including hole diameter, pitch, row spacing and edge distances. Tin plating can be added after machining.
Can copper lugs be bolted to an aluminium ground bar?
Yes, if the joint is designed for it. Use tin-plated bar or bimetallic washers, AL/CU-rated lugs, joint compound and Belleville washers, and torque to the lug maker value. Keep bare copper-to-aluminium joints out of wet locations.
Do you supply insulators, brackets and lug kits?
No. Metline supplies the aluminium bar, cut, drilled and plated to order. Insulating supports, brackets, fasteners and lugs are sourced by the panel builder or installer to suit their enclosure system.
Ordering aluminium ground bars?
Send the alloy, bar size, length, hole layout, plating and quantity. We check the drawing and reply with a delivered price.
