Aluminum Transformer Set Screw Bars — also known as Aluminum Set Screw Bus Bars, Aluminum Multi-Tap Connectors, or Aluminum Mechanical Splice Connectors — are versatile, high-conductivity current-carrying bars used to connect multiple conductors at transformer terminals, distribution panels, switchgear, and power distribution equipment. Cable Glands India manufactures and exports precision Aluminum Set Screw Bars that meet the demanding requirements of the US electrical market and conform to global standards including UL 486A and CSA standards.
What Are Aluminum Transformer Set Screw Bars?
An Aluminum Set Screw Bar is a precisely machined, multi-hole electrical connector bar designed to accept and mechanically terminate multiple conductors simultaneously using set screws (machine screws that bear directly onto the conductor). Each hole in the bar accommodates one conductor, and the set screw — typically a cup-point or cone-point machine screw with a hex socket — is tightened onto the conductor to create a secure, low-resistance electrical connection without the need for crimping tools.
In transformer applications, Set Screw Bars are used at the low-voltage (LV) secondary terminals of distribution transformers (typically 120/240V, 208V, 480V systems in the USA) to distribute the transformer output to multiple circuit breakers, bus bars, or feeder cables. They are also used in switchgear, padmount transformers, unit substations, and motor control centers (MCCs).
Key Features of Aluminum Set Screw Bars
- Material: High-conductivity aluminum alloy — AA6061-T6 or AA1350-H19 (electrical grade) — offering the ideal balance of conductivity, strength, and corrosion resistance.
- Set Screw Design: Grade 5 or Grade 8 hex socket set screws in zinc-plated or stainless steel finish for reliable conductor clamping torque.
- Multiple Tap Holes: Available in 1-hole through 12-hole configurations to accommodate multiple taps.
- Conductor Range: Compatible with conductor sizes from #14 AWG through 1000 kcmil (depending on size).
- AL/CU Rated: Suitable for use with both aluminum and copper conductors (when listed AL/CU rated).
- Tin Plating Option: Tin-plated aluminum bars for enhanced contact resistance and bi-metallic compatibility.
- Mounting: Pre-drilled mounting holes for panel or enclosure bus bar mounting.
- Insulation: Bare aluminum (standard) or with insulating sleeve/cover for safe working environments.
Aluminum Set Screw Bar Material Grades & International Equivalents
The selection of aluminum alloy for electrical Set Screw Bars is critical to ensure adequate conductivity, mechanical strength, and corrosion resistance. Here is a comprehensive cross-reference of the alloy grades commonly used:
| Property | USA (AA/ASTM) | India (IS/BIS) | UK/Europe (EN) | Germany (DIN) | ISO |
|---|---|---|---|---|---|
| Electrical Grade Aluminum | AA 1350-H19 (EC Aluminum) | IS 5082 Grade E91E | EN AW-1350A / EN 13599 | AlE / E-Al | ISO 209 Al 99.5E |
| Structural Grade Aluminum | AA 6061-T6 | IS 733 / IS 1285 HE20TF | EN AW-6082 / EN AW-6061 | AlMgSi1 / 3.2315 | ISO 209 AlMg1SiCu |
| Conductivity (%IACS) | AA1350: 61% | AA6061: 43% | E91E: ~61% | 1350A: 61% | E-Al: 61% | Al 99.5E: 61% |
| Tensile Strength | AA1350: 159 MPa | AA6061-T6: 310 MPa | E91E: ~160 MPa | HE20TF: 260–310 MPa | 1350A: ~160 MPa | E-Al: ~160 MPa | — |
| Set Screw Grade | ASTM A574 Gr.8 (Stainless: ASTM F880) | IS 1367 Cl.8 / IS 3741 | ISO 4029 / EN ISO 4026 | DIN 916 / DIN 6912 | ISO 4026 / ISO 4029 |
| Tin Plating (on AL) | ASTM B545 | IS 1573 | BS EN ISO 2093 | DIN 50961 | ISO 2093 |
| RoHS Compliance | Yes | Yes | Yes | Yes | EU 2011/65/EU |
Aluminum Set Screw Bar Configurations & AWG/kcmil Ratings
Set Screw Bars are categorized by the number of taps and the conductor size range they accommodate. The following table provides a guide to common configurations:
| Configuration | Conductor Range (AWG/kcmil) | Number of Set Screws per Hole | Typical Application | Voltage Rating |
|---|---|---|---|---|
| Single Tap | #6 AWG – 350 kcmil | 1–2 | Single cable termination at transformer lug | 600V, 1000V |
| 2-Hole Multi-Tap | #14 AWG – 2/0 AWG | 1 per hole | Branch circuit distribution | 600V |
| 4-Hole Multi-Tap | #14 AWG – 4/0 AWG | 1 per hole | Panel sub-feeders | 600V |
| 6-Hole Multi-Tap | #14 AWG – 250 kcmil | 1 per hole | Transformer secondary distribution | 600V |
| 8-Hole Multi-Tap | #14 AWG – 250 kcmil | 1 per hole | MCC & switchgear bus connections | 600V / 1kV |
| 10-Hole Multi-Tap | #14 AWG – 4/0 AWG | 1 per hole | Large distribution panels | 600V |
| 12-Hole Multi-Tap | #14 AWG – 1/0 AWG | 1 per hole | High-density tap applications | 600V |
Related Products to Aluminum Set Screw Bars
Copper Set Screw Bars
For applications where maximum conductivity is required, or where aluminum conductors must be transitioned to copper bus bars, Copper Set Screw Bars (manufactured from C11000 / ETP Copper or C10200 / OF Copper) provide superior electrical performance. Cable Glands India supplies both aluminum and copper set screw bar configurations to suit all customer requirements.
Aluminum Compression Lugs
Aluminum Compression Lugs (mechanical lugs / crimp lugs) work alongside set screw bars in transformer termination assemblies where a crimp connection is preferred over a set screw connection. Available in long-barrel and standard-barrel configurations for conductor sizes from #6 AWG to 1000 kcmil.
Transformer Neutral Bars
Aluminum Neutral Bars are used at the transformer secondary neutral terminal to connect multiple neutral conductors. Similar in construction to set screw bars but specifically configured for neutral assembly mounting.
Aluminum Ground Bars
Aluminum Ground/Earth Bars provide a common grounding point for multiple equipment ground conductors in distribution panels, transformers, and switchgear. Available with pre-drilled mounting holes and insulated standoff options.
Bus Bar Hardware & Mounting Brackets
Complete bus bar assembly hardware including insulated mounting standoffs, inter-phase spacers, bus bar clamps, and stainless steel hardware sets are available to complement the aluminum set screw bar range.
Applications of Aluminum Transformer Set Screw Bars
Aluminum Set Screw Bars are specified across a wide range of power distribution applications in the USA and internationally:
- Pad-Mount Transformers: Secondary terminal connections in 15kV–35kV distribution transformer tanks serving commercial and industrial customers.
- Dry-Type Transformers: Terminal connections in 480V–600V dry-type transformers for building power distribution.
- Switchgear & Switchboards: Bus tap connections for branch circuit feeders in medium and low-voltage switchgear lineups.
- Motor Control Centers (MCCs): Horizontal bus tap connections in MCC bucket assemblies.
- Residential & Commercial Load Centers: Neutral bars in residential load centers (100A–400A service panels).
- Industrial Panel Boards: Multi-tap connections for large industrial power distribution panels up to 4000A.
- Renewable Energy: DC bus bar connections in solar inverter and battery storage systems.
- Data Center Power: PDU (Power Distribution Unit) bus bar tap connections.
Standards & Certifications for Aluminum Set Screw Bars
Aluminum Set Screw Bars from Cable Glands India are manufactured to meet the following applicable standards for the USA and global markets:
- UL 486A-486B – Wire connectors for use with aluminum and/or copper conductors (USA)
- CSA C22.2 No. 65 – Wire connectors (Canada)
- ANSI C119.4 – Connectors for use between aluminum-to-aluminum or aluminum-to-copper conductors
- ASTM B800 – Aluminum conductors, compact round (for conductor compatibility)
- IEEE C2 (NEC Table 310.15) – National Electrical Safety Code ampacity compliance
- IEC 61238-1 – Compression and mechanical connectors for power cables (international)
- RoHS Directive 2011/65/EU
- REACH Regulation
Why Choose Cable Glands India for Aluminum Set Screw Bars?
Cable Glands India stands apart as a trusted manufacturer and exporter of Aluminum Set Screw Bars for the US and global electrical market:
- Precision CNC Machining: All set screw bars are CNC-machined from certified aluminum extrusion or bar stock, ensuring precise hole sizing, thread accuracy, and surface finish for reliable conductor termination.
- Certified Alloy Materials: We use certified AA1350-H19 (EC grade) and AA6061-T6 aluminum, with full material traceability and batch-specific test certificates.
- AL/CU Dual Rating Capability: Tin-plated versions tested and listed for both aluminum and copper conductor compatibility.
- Competitive Export Pricing: Direct manufacturer pricing that gives USA distributors and transformer manufacturers a significant cost advantage over domestic equivalents.
- Custom Configurations: We manufacture custom set screw bars to client drawings — any number of tap holes, any conductor range, any mounting configuration.
- Fast Turnaround: Standard configurations in stock; custom orders in 3–5 weeks.
- Full Documentation: UL test reports, material certificates, RoHS/REACH declarations, and packing documentation for smooth US customs clearance.
- Dedicated Technical Support: Our engineering team assists with product selection, current-carrying capacity calculations, and application-specific requirements.
Frequently Asked Questions – Aluminum Transformer Set Screw Bars
Q1. What is a Transformer Set Screw Bar used for?
A Transformer Set Screw Bar is used to mechanically and electrically connect multiple conductors to a common point on a transformer terminal, bus bar, or distribution panel. The bar features multiple holes — each sized to accept a specific range of conductors — and set screws that clamp down on each conductor to create a secure, low-resistance connection. They are widely used in pad-mount transformers, dry-type transformers, switchgear, and load centers across the USA.
Q2. Why is aluminum used for Set Screw Bars rather than copper?
Aluminum is used for Set Screw Bars primarily because of its favorable weight-to-conductivity ratio and significantly lower cost compared to copper. AA1350-H19 aluminum has an electrical conductivity of approximately 61% IACS — adequate for most power distribution applications. Aluminum bars also offer excellent corrosion resistance when properly alloyed and are approximately 70% lighter than equivalent copper bars, making them easier to handle and install in large transformer assemblies.
Q3. Can aluminum set screw bars be used with copper conductors?
Yes, but with an important qualification: only AL/CU-rated (dual-rated) set screw bars should be used with copper conductors on aluminum bars. These bars feature tin plating or other bi-metallic treatment to prevent galvanic corrosion at the aluminum-copper interface. Standard (unplated) aluminum bars are intended for aluminum conductors only. Always check the product listing to confirm AL/CU compatibility before connecting copper conductors to an aluminum bar.
Q4. What AWG sizes do aluminum set screw bars accommodate?
Aluminum Set Screw Bars are available in a wide range of conductor sizes. Depending on the specific product, hole sizes accommodate conductors from #14 AWG (small control wiring) up to 1000 kcmil (large power feeder cables). Multi-tap bar configurations allow different holes in the same bar to accept different conductor size ranges. Cable Glands India offers bars sized to any AWG/kcmil specification required by the customer.
Q5. What voltage ratings are aluminum set screw bars available in?
Standard Aluminum Set Screw Bars are rated for 600V AC (which covers the vast majority of USA distribution applications: 120V, 208V, 240V, 277V, 480V, and 600V systems). Higher voltage ratings of 1kV, 2kV, and up to 35kV are available for medium-voltage applications in padmount and substation transformers. Higher-voltage bars feature increased creepage distances and may incorporate insulating barriers between phases.
Q6. What is the difference between a set screw bar and a compression (crimp) lug?
A set screw bar uses mechanical set screws to clamp conductors in place — no special tooling is required beyond a torque wrench and hex key. A compression (crimp) lug requires a hydraulic or mechanical compression tool to permanently deform the connector barrel around the conductor. Set screw connections offer the advantage of being easily re-tightened or re-terminated in the field; compression connections are generally considered more reliable for permanent, high-current applications. Both types are used in transformer terminations depending on the specification.
Q7. What torque should be applied to set screws in aluminum set screw bars?
Set screw torque values are specified by the manufacturer and are typically listed on the product label or in the installation instruction sheet. For aluminum conductors in particular, it is critical to apply the specified torque — under-torquing creates a high-resistance connection, while over-torquing can damage the conductor or strip the thread. Typical torque values for set screws on aluminum bars range from 35 to 375 in-lbs (4 to 42 Nm) depending on the screw size and conductor size. Always follow the manufacturer’s torque specifications and use a calibrated torque wrench.
Q8. Do aluminum set screw bars require an oxide inhibitor (joint compound)?
When connecting aluminum conductors to aluminum set screw bars, the use of an oxide inhibitor (also called anti-oxidant joint compound, e.g., Noalox, Penetrox) is strongly recommended. Aluminum naturally forms an insulating oxide layer on its surface. Joint compound penetrates and prevents this oxide layer from forming at the electrical contact interface, ensuring long-term low-resistance connections and preventing progressive corrosion. Many UL-listed aluminum connector products specify that joint compound must be used to maintain the listing.
Q9. Are your aluminum set screw bars listed to UL 486A?
Cable Glands India manufactures aluminum set screw bars to the dimensional and material specifications of UL 486A-486B. For specific UL listing marks, we can provide products that have been third-party tested by accredited laboratories. Customers requiring formal UL listing marks on products for NEC-regulated installations should specify this at the time of order, and we will arrange appropriate third-party certification. Contact our sales team for details on available certifications for your specific application.
Q10. How are aluminum set screw bars mounted in transformer compartments?
Aluminum Set Screw Bars are typically mounted to the transformer compartment wall or mounting plate using pre-drilled mounting holes in the bar and insulating standoff bushings. The standoffs provide electrical isolation between the bar and the mounting surface. Mounting holes are typically 1/4″ or 3/8″ diameter, and stainless steel machine screws are used for corrosion resistance. Bar mounting height and spacing must comply with the required creepage and clearance distances per the applicable voltage rating.
Q11. Can aluminum set screw bars be used in outdoor transformer applications?
Yes. Aluminum alloy (especially AA6061-T6) has excellent natural corrosion resistance due to its stable oxide layer, making it suitable for outdoor transformer enclosures. For highly corrosive environments (coastal, industrial), tin-plated aluminum set screw bars provide additional protection against corrosion and bi-metallic galvanic action. Enclosure IP ratings and ventilation requirements for the transformer compartment should also be considered to protect the bar and terminations from direct moisture exposure.
Q12. What is the current-carrying capacity (ampacity) of aluminum set screw bars?
Ampacity depends on the cross-sectional area of the aluminum bar, ambient temperature, installation conditions, and any de-rating factors. For AA1350-H19 aluminum at 75°C conductor temperature (standard NEC rating basis), a 1″ x 1/4″ bar carries approximately 250–350A; a 2″ x 3/8″ bar carries approximately 600–800A. Precise ampacity calculations should be performed per NEC Table 310.15 or IEEE C2 guidelines, considering the specific cross-section, temperature rise, and installation environment. Contact our technical team for assistance with ampacity calculations for your specific application.
Q13. Do you supply custom-length aluminum set screw bars?
Yes. Cable Glands India manufactures custom-length aluminum set screw bars to customer drawings or specifications. We can machine bars to any length, any number of tap holes, any hole diameter and spacing, and any mounting hole configuration. Custom bars are available in both AA1350-H19 (EC grade) and AA6061-T6 (structural grade) aluminum with optional tin plating. Lead time for custom bars is typically 3–5 weeks depending on complexity and quantity. Please submit your drawing or specification for a quotation.
Q14. What packaging and shipping options are available for USA orders?
Aluminum Set Screw Bars are packaged individually in protective poly bags, then in labeled inner boxes, and outer export cartons. Full documentation (CoC, MTC, packing list, commercial invoice) is provided with every shipment. Shipping options to the USA include sea freight (LCL for smaller orders, FCL for large volumes), air freight for time-critical orders, and DHL/FedEx/UPS courier for samples and small quantities. We work with established freight forwarders experienced in US import procedures to ensure smooth delivery and customs clearance.
Contact Cable Glands India for Aluminum Set Screw Bars
Whether you need standard stock configurations or custom-engineered Aluminum Transformer Set Screw Bars, Cable Glands India is your reliable manufacturing partner. We serve transformer OEMs, electrical panel builders, switchgear manufacturers, and distributors across the USA with competitive pricing and consistent quality.
📧 Email: sales@cableglandsindia.com
📞 Phone: +91 22 4344 9300
🌐 Website: www.cableglandsindia.com