Electrical enclosures are indispensable in electrical applications, and the material causes multiple differences in their functions. If you are hesitating over which kind to purchase, read this article for details of the differences between plastic and metal electrical boxes, and you may be inspired.
Now let’s dive in.
What is an Electrical Enclosure?
An electrical enclosure is a box designed to contain and protect electrical equipment from environmental influences such as dust, moisture and chemicals, which is very practically used in residential, commercial and industrial electrical applications. It attaches switches, knobs and displays.
It is multifunctional, except for protecting against environmental hazards, it can also reduce the risks of corrosion, overheating or mechanical failures, improve system lifespan and reliability, and enhance safety by preventing electrical users from electrical shock. Some complex-designed electrical boxes can even support heat dissipation and reduce electromagnetic interference (EMI) and radio frequency interference, which is vital in hazardous areas such as petrochemical plants and coal mines.
According to different installation ways, electrical enclosures can be classified into various types like wall-mounted, floor-standing, pole-mounted, flush-mounted, surface-mounted, and free-standing, and they also various shapes including standard rectangular, square, round or octagonal and ceiling boxes.
If classified by materials, electrical enclosures can be divided into plastic and metal; both have their own characteristics, which will be introduced in the following part at length.
Plastic Electrical Enclosures
The first kind of electrical enclosure is the plastic electrical enclosure, which is light, corrosion-resistant and price-effective, always applied in residential areas and followed by many DIY enthusiasts and electrical contractors.
The plastic used for making the electrical enclosure is rigid plastic, which can be mostly divided into ABS, PVC, Polycarbonate and Fiberglass. Their composition includes flame-retardant additives and stabilizers, which can prevent the material from degrading over time. The characteristics of different kinds of plastics are also various, and the comparison is listed in the following chart.
| Characteristics | ABS | PVC | Polycarbonate | Fiberglass |
| Material | Composite of acrylonitrile, butadiene, and styrene plastics. | Composite of chlorine and carbon. | Made of just a single type of plastic, giving a strong bond to its molecules, leading to better strength and stability, and it’s light. One of the easiest materials to modify | Composite material made from fine glass fibers reinforced with a plastic resin. |
| Tensile Strength | 4,500 psi | 6,300 psi | 10,000 psi | 9,000-18,000 psi High-performance grades like S-glass can reach over 650,000 psi. |
| Impact Strength (notched Izod impact strength) | 4 ft-lb/in | 10 ft-lb/in | 12 ft-lb/in | 4-16 ft-lb/in |
| UV Resistance | Not UV resistant discolor and degrade | can be applied to direct sunlight | UL 746C f1 (Capable of enduring long-term exposure to outdoor ultraviolet radiation, rain and moisture erosion) | Has natural UV resistance, but long-term exposure degrades the resin, causing fiber frosting (fading, chalkiness, and weakening of the material’s structural integrity) |
| Flame Retardancy | Can reach UL94 5Va by adding the thickness or special coating. (If the UL Flame reaches 5Va, the enclosure won’t be burned through, melted, and can self-extinguish after catching fire) | UL94 5Va (the highest level of UL Flame Retardancy) | UL94 5Va (the highest level of UL Flame Retardancy) | Can reach UL94 5Va through the use of a composite with a flame-retardant resin system and reinforcing fibers, like carbon fiber. A standard fiberglass can not reach this rating. |
| Thermal Aging (RTI, Relative Thermal Index) | 185° F | 140° F | 221° F | 176° F-293° F |
| Color | Opaque beige. Often colored gray or black. | Water clear, white, black, or grey. | Water clear (this color makes polycarbonate able to be made into transparent covers, very convenient for you to check the internal condition.) | Off-white or yellowish in itself, or other colors that are used for various applications. |
Taken together, ABS is more suitable for making boxes for indoor applications, while polycarbonate is relatively more suitable in worse environmental conditions for its better strength, UV resistance (related to the ability for outdoor application), flame retardancy, thermal aging (related to heat tolerance) and colorability.
Metal Electrical Enclosures
Another choice is the metal electrical enclosure. Before the appearance of the plastic electrical enclosure, the metal electrical enclosure was the standard configuration in the market. It is sturdy and durable with high reliability, always applied in commercial and industrial areas, providing outstanding protection in demanding applications.
Metal electrical enclosures can also be divided into three types according to different materials: Carbon steel, Stainless steel, and Aluminum.
| Characteristics | Carbon steel | Stainless steel | Aluminum |
| Price | Most price-effective | Less price-effective | Price-effective |
| Weight | Lighter than others. | ||
| Corrosion Resistance | Need to coat to resist corrosion. | High corrosion resistance. It has antibacterial and antifungal performance for its pore-free characteristic, ideal for application in medical, pharmaceutical and food industries. | Natural rust prevention |
| Electromagnetic interference | Shield against electromagnetic interference. | ||
| Heat conduction | Nice heat conduction property. Have effective heat dissipation. |
Comprehensive Comparison between Plastic & Metal
Knowing the differences between plastic and metal enclosures helps you directly notice the pros and cons of each. The following comparison chart clearly presents these differences for you.
| Plastic Electrical Enclosure | Metal Electrical Enclosure | |
| Price | Cost less | Costs more, but has long-term value for its longer service life. Aluminum can be more cost-effective. |
| Weight | Better. Light-weight, so it’s easier for transportation and installation. | Heavier than plastic, making the transportation and installation process more complicated. Aluminum enclosures are lighter. |
| Processability | Short processing cycle and high turnover rate.
| It cannot be melted, more suitable for high-temperature conditions. |
| Electrical conductivity | Plastic is non-conducting, which makes it safer and ideal for humid environment applications. | Conductive. Not suitable for use in damp environments. |
| Grounding |
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| Installation | Better. Easier to install, simplify or even speed up the installation process.
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| Sealing Performance | The plastic box body and the box cover are integrally formed through large-scale injection molding, with few and neatly arranged seams, but its sealing performance is limited by the material. Under continuous high temperatures, the plastic box body may slightly deform, damaging the flatness of the sealing surface and causing leakage, while at low temperatures, both the plastic and the sealing strip will become hard, thereby affecting the sealing effect. | The metal structure has high strength and is not prone to deformation at high temperatures, which enables it to maintain the flatness of the sealing surface and the pressure. |
| Static Electricity | Better. Prone to accumulating static electricity. | Does not accumulate static electricity by itself. |
| Electrical Load | Can not bear high-power electrical load. | Better. Can bear a larger electrical load; for example, it’s suitable for installing ceiling fans or large lamps. |
| Corrosion Resistance | Better. High corrosion resistance and very suitable for damp environments. It can resist most types of corrosion like rusting or chemicals, which is very useful when exposed to harsh environments or placed in highly demanding conditions such as those in the chemical industry. |
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| Heat Resistance | If the temperature is too high, the plastic may melt or crack, thereby damaging the internal electronic components. | Better. Can bear high temperatures or temperature changes. |
| Sturdiness | Not as good as metal electrical boxes.
| Better. Highly sturdy. Hard to bend, deform, twist or flatten. |
| Impact Resistance |
| Better. Can withstand huge impact forces. |
| Durability | Not as good as metal, but enough for not overly harsh applications | Better durability and longer service life |
| Fireproof | High-quality plastic boxes have a better flame-retardant ability, such as UL 94 5VA, which depends on their resin and flame-retardant grade. | Better. Metal itself does not burn and can withstand higher temperatures, becoming a better choice in flammable applications. |
| Ultraviolet-proof | High-quality plastics have excellent UV resistance and can effectively prevent the rapid aging of the box, while inferior plastics may age more quickly, and ultraviolet rays may cause the plastic molecule chains to break, making the material brittle and reducing its impact strength. | The paint film of the metal may suffer from problems such as fading, loss of luster and powdering due to prolonged exposure to sunlight, but the structural strength of the metal matrix itself is not affected by ultraviolet rays, resulting in little effect on the structural strength of the box. |
| Versatility | No electromagnetic shielding function. | Have nice Electromagnetic interference (EMI), radio frequency interference (RFI) shielding performance and heat dissipation. Aluminum especially has excellent heat dissipation, which can help keep the operating temperature of sensitive electronic components within a safe range. |
| Appearance and Design Flexibility | Great design options and flexibility. Can be made into various shapes and sizes, and can be color-coded or branded. Complex features, shapes, characters and surface textures can all be easily incorporated into the molds used for plastic part production. |
These all will increase manufacturing time and costs. |
| Maintainance | Low requirements for maintenance, but it may need to be changed if it is broken or aging. | Can last longer but you may need to regularly check it if it is put in a humid environment. |
Applications of Plastic and Metal Electrical Enclosures
All of the differences between plastic and metal boxes determine their difference in applications. Learning about their applications can help you to more easily make your choice.
Plastic Electrical Enclosures
- Outdoor installation
For daily outdoor use, more people choose plastic boxes for their lower cost and nice protective properties against rust, moisture, ultraviolet rays and dust.
- Consumer Electronic
Plastic electrical boxes are lightweight, portable and have high design flexibility, and their non-conductive characteristics ensure safety, so they are nice for the application of daily use electronic equipment.
- Marine and offshore industries
The excellent corrosion resistance of the plastic electrical enclosure plays an important role in resisting the erosion caused by seawater and highly corrosive chemicals.
- Food Processing
Plastic electrical enclosures are easy to clean because they are non-conductive and do not rust, which is very practical in protecting food safety. Besides, their chemical corrosion resistance and moisture-proofing performance can ensure the purity of the production process.
- Chemical Plant
The nice corrosion resistance of the plastic box makes it a better choice for use in chemical plants and sewage treatment plants.
- Auto Industry
Using plastic boxes to wrap electronic components in auto parts can prevent rust and reduce vibration.
- Renewable Energy Sources
Plastic electrical enclosures are also usually applied to protect components of solar and wind energy systems due to their waterproof and UV-resistant properties.
Metal Electrical Enclosures
- Manufacturing Industry
Metal electrical enclosures are widely used in manufacturing to protect the electrical system in the machine and ensure the safety of the components and the smooth operation of the machine.
- Energy
Metal electrical enclosures used in the energy field prevent outdoor ultraviolet rays, rain, snow, sandstorms, salt fog (in coastal areas) and extreme temperatures, and provide excellent heat dissipation and shield the electromagnetic interference.
In nukes, their nice grounding performance is of great importance in ensuring the safety of personnel and equipment.
Metal electrical enclosures are used in telecom areas for their functions of preventing electromagnetic interference (EMI) and radio frequency interference (RFI)
- Transportation
The systems used for signal management and traffic control in transportation are protected by metal electrical enclosures.
- Electromagnetic sensitive environment
Sensitive electronic devices such as frequency converters, PLCs, and servo drives require metal enclosures to shield against electromagnetic interference.
- Flammable environment (Petrochemical plant, gas station, flour processing plant, spray painting room…)
Metal electrical enclosures are standard and mandatory requirements in flammable environments, and marked with the corresponding certification marks (such as ATEX, IECEx, UL). They can accommodate internal explosions, safely discharge static charges, help control the surface temperature, and provide strong physical protection.
How to Choose the Best One for You?
After reading the above part, you may have a comprehensive knowledge of the characteristics of plastic and metal electrical enclosures now, so here is the most critical question: which one is more suitable for you? When considering this question, you can take the following factors into account, which not only help you decide the material but also cover other critical factors in choosing electrical enclosures:
Factors Related to Material Choosing
- Cost: The first step is to estimate the budget you want to use for purchasing electrical enclosures. You can get a quote from the supplier and evaluate the initial purchase cost, installation cost and potential maintenance cost for each material option. Plastic boxes are more affordable. Metal ones have a higher initial investment, but are more durable and have lower maintenance costs.
- Installation Environment: The environment largely decides the requirements of the electrical boxes’ corrosion-resistant ability and sealing grade. If the enclosure is exposed to a demanding industrial environment with extremely high strength requirements, or outside with corrosive chemicals, high humidity or explosive gases, choosing metal boxes is better than plastic.
- Physical protection: If the electrical enclosure needs to be placed in areas with high foot traffic or those prone to mechanical damage, you need to choose boxes with better impact resistance, tamper resistance and vandalism resistance.
- Heat dissipation and electromagnetic interference: If the electrical enclosure needs to be applied in hazardous areas, we recommend metal boxes for their good heat dispersion, and you can add cooling fans or heat sinks to control the temperature and shielding to reduce electromagnetic interference (EMI) if necessary.
- Application: Both plastic and metal electrical boxes have their own suitable and common applications (like the above part mentioned). Usually, when you need a box for commercial or industrial or electrical systems involving metal-sheathed cables, the metal ones would be a better choice. Samely, if you are wiring an unfinished basement where the conduits are exposed, a metal electrical box is crucial for ensuring the safety and integrity of the maintenance system. While If you are considering a residential box and using non-metallic sheathed wires, then plastic boxes might be more suitable, because they are lightweight and easy to use, and are perfect for installing light switches, sockets, or small lamps.
Other Factors
- Space: How large is the space you have prepared to install the electrical box? The space should not only contain the size of the box itself, but also the space for future expansion (used for extra wiring, upgrades and ventilation). Besides, an extra space also enhances accessibility for checking and maintaining the box.
- Certification: The electrical enclosure must comply with standards such as UL, IEC or CE, depending on your location. This is a necessary requirement for safety. For example, metal and plastic electrical boxes can both be used in conjunction with firestopping, which is essential for preserving the fire-resistance integrity of walls and ceilings.
- Design details: Many details may largely enhance functionality, safety or usability of the box, such as transparent insulating covers (Polycarbonate), safety locks, Detachable installation rail, hinges, Built-in lighting lamp, waterproof sealing rings, ventilation systems, etc.
- IP Rating: This is what you must consider when choosing electrical enclosures. A high IP rating is vital in demanding applications for enclosures.
FAQ
What is RTI?
RTI, a relative thermal index, represents its long-term heat resistance, defining the upper temperature limit for continuous use without failing.
What is NEMA and IPrating?
NEMA (National Electrical Manufacturers Association) and IP (Ingress Protection) represent the electrical enclosures’ level of protection.
NEMA is the standard of North America, including NEMA 1, NEMA 2, NEMA 3, NEMA3X, NEMA3RX, NEMA 3R, NEMA3S, NEMA 4, NEMA 4X, NEMA 5, NEMA6, NEMA6P, NEMA 12 and NEMA 13. The protective ability increases with the NEMA rating.
IP is the global standard. It is composed of two numbers, with the first number (0/5/6) representing the ability to protect against solids, and the second number (0/5/6/7) representing anti-liquid corrosion performance. A bigger number indicates better protective properties. For example, IP66 indicates that the box is completely dust-proof and can withstand a significant amount of water splashing.
Plastic vs Metal: Which One is More Weatherproof?
Comprehensively speaking, both plastic and metal enclosures can achieve extremely excellent weather resistance performance, but their strengths and potential weaknesses are different. High-quality plastic enclosures are better at corrosion and rust prevention, while metal enclosures are better in electromagnetic shielding, physical damage prevention, and high-temperature resistance.
Can You Mix Plastic and Metal Electrical Boxes?
Yes. A hybrid enclosure combines the strength, shielding and grounding capabilities of metal boxes, and the insulation, corrosion resistance and lightweight advantages of plastic boxes. For example, you can customize an electrical enclosure with a metal frame and a plastic panel.
What is the Lead Time of Electrical Enclosures?
Specific lead time can range from a few days to many months, which is decided by the complexity of the enclosure design and current supply chain conditions.
KDM—Making Ideal Enclosures for You
Not only in the electrical area, metal enclosures are widely applied in our lives. KDM, a professional sheet metal fabrication factory in China, can offer you customized services for carefully designed metal enclosures. We have professional teams waiting for your requirements all the time, and our metal sheeting service can maximize the satisfaction of your needs. If you want to custom or purchase metal enclosures, never hesitate to contact us!