What is Sandwich Type Busway? A Complete Guide vs. Cable & Selection Tips
In modern high-rise buildings, industrial plants, and data centers, Sandwich Type Busway is rapidly replacing traditional power cables for high-current distribution. But what exactly is Sandwich type busway, and why are engineers making the switch?
This article provides an in-depth analysis of Sandwich type busway, including its advantages over cable, key technical parameters, and how to select the right system for your project.
What is Sandwich Type Busway?
sandwich type busway is an efficient power transmission system. It consists of copper or aluminum conductors insulated with high-grade materials (such as polyester film) and enclosed in a grounded metal housing.
The defining feature of sandwich type busway is the minimal air gap between conductors and between conductors and the enclosure. This "sandwich" design maximizes heat dissipation while significantly reducing overall volume.
Unlike air-type busway, Sandwich type busway has no internal air gaps. This provides higher dynamic and thermal stability and greater current-carrying capacity. It is the preferred choice for basements, electrical rooms, high-rise risers, and harsh industrial environments.
Why Choose Sandwich Type Busway Over Cable? 4 Key Advantages
For large-current transmission (typically above 630A), sandwich type busway offers overwhelming advantages compared to traditional cable systems.
1. Higher Current Capacity & Lower Voltage Drop
When transmitting high currents (e.g., 1600A or more), multiple parallel cables suffer from eddy currents and the skin effect, leading to energy loss.Sandwich type busway uses rectangular conductors with uniform current density. Even over long distances, voltage drop remains minimal—ideal for large factories and high-rise buildings.
2. Superior Heat Dissipation & Longer Service Life
Cable insulation acts as a thermal barrier, trapping heat and accelerating aging (typical cable lifespan: 25-30 years). In contrast, the metal enclosure of Sandwich type busway acts as a heat sink. Combined with high-temperature insulation (rated up to 130°C+), sandwich type busway can last 50+ years with proper maintenance.
3. Easy Tap-Off & Flexibility
Once cables are installed, adding a new outlet (e.g., for an additional machine) requires costly rewiring.Sandwich type busway features tap-off boxes that allow you to add or move power take-off points anywhere along the busway run—like building blocks. This is invaluable for factories with changing production layouts.
4. Space Saving & Neat Installation
Vertical riser space in high-rise buildings is extremely valuable. To carry 2000A, cables may require 4–6 runs in parallel, consuming massive space. A single Sandwich type busway handles the same current cleanly, with a tidy, professional appearance that simplifies fire safety inspections.
Key Technical Parameters & Selection Criteria
When selecting Sandwich type busway, pay close attention to the following specifications to avoid costly mistakes:
| Parameter | Description | Selection Tip |
| Rated Current | 250A to 6300A+ | Choose with a 10-15% margin above calculated load. |
| Ingress Protection (IP) | IP54: Dust & splash proof (indoor). | Use IP65+ for chemical plants, tunnels, or outdoor links. |
| Insulation Material | Polyester film (Class B/F) or epoxy resin. | Epoxy resin cast is best for corrosive, humid, or explosion-proof areas. |
| Enclosure Material | Aluminum alloy or galvanized steel. | Aluminum alloy is lighter, corrosion-resistant, and non-magnetic (reduces eddy currents). |
| Temperature Rise Limit | IEC/GB standards: enclosure ≤55K, joints ≤70K. | Lower temperature rise = longer life and lower losses. |
Common Applications
High-Rise Buildings: Offices, hotels, hospitals — from transformer room to floors.
Industrial Plants: Automotive assembly, machining, electronics — powering production lines.
Data Centers: Reliable, low-impedance power to server racks.
Commercial Complexes: Shopping malls, airports — for large HVAC and lighting loads.
Installation & Maintenance Best Practices
Although Sandwich type busway is robust, joint connection quality is the lifeline of the system.
Torque Control: Always use a torque wrench to tighten joint bolts to the manufacturer’s specified value. Insufficient torque causes high contact resistance and overheating.
Water & Fire Protection: When busway passes through floors or walls, install transition boxes and use proper firestopping materials.
Insulation Testing: Before energizing, use a megohmmeter to test insulation resistance between phases and phase-to-ground to ensure no moisture ingress.
Summary
sandwich type busway offers superior high-current capacity, long service life, and outstanding flexibility. While the initial material cost may be higher than cable, its excellent heat dissipation, low failure rate, and 50+ year lifespan provide a significantly lower Life Cycle Cost (LCC) .
Final Recommendation:
For projects with current >630A and multiple tap-off points → prioritize Sandwich type busway.
For high humidity, corrosive, or outdoor environments → specify epoxy resin cast sandwich type busway.