comparison of plastic and metal boxes for vending machines 

Plastic vs metal: what to choose for protecting circuit breakers

The choice between a plastic and metal vending machine box is not just a matter of aesthetics, but a critical decision that affects fire safety and the durability of electrical wiring. In our practice, we have seen cases where saving 500 rubles on a housing led to complete burnout of the panel due to the destruction of plastic under the influence of ultraviolet radiation or mechanical shock. Let's give a straight answer right away: for indoor installation in residential premises with a dry microclimate, high-quality non-flammable plastic (ABS) is optimal, while for streets, production workshops, garages and places with a risk of vandalism, the only correct solution is powder-coated metal. This article will help you avoid fatal mistakes when completing an electrical panel.

Fundamental Material Differences

The electrical products market offers two main ways to protect modular equipment: polymers and steel. Understanding the physical and chemical properties of these materials allows the engineer to predict the behavior of the shield after 10–15 years of operation. Plastic boxes, most often made of ABS plastic or polycarbonate, have high dielectric strength and ease of installation. However, their main enemy is time and the external environment. Cheap plastic turns yellow over time, becomes brittle and loses impact resistance. Metal casings, usually made of cold-rolled steel with a thickness of 0.8 to 1.2 mm, provide mechanical armor for machine guns. Their weakness is corrosion when the protective layer is damaged and the need for high-quality grounding.

It is important to note that the concept of “plastic” is too general. There is a difference between budget polystyrene boxes, which melt at temperatures above 70°C, and professional self-extinguishing polycarbonate boxes, which can withstand heat up to 650°C without flame propagation. Likewise, metals vary: galvanized steel resists rust better than black, but requires more complex edge finishing. In one of our projects at a warehouse in Novosibirsk, the client insisted on installing a plastic shield in an unheated room. After three winters, temperature changes from -30°C to +20°C led to the formation of microcracks in the case, through which dust and moisture penetrated, causing a short circuit. This cost the company a line downtime for two days.

Comparison of plastic and metal boxes for vending machines based on key parameters

To make an informed decision, it is necessary to consider the technical characteristics of both types of housings in the context of actual operating conditions. We have prepared a detailed table, based on laboratory tests and field observations, that shows where each material exhibits its strengths and weaknesses.

Analyzing the table, it becomes obvious that the choice is dictated by the environment. If you are installing a panel in an apartment where there is no risk of being hit by a hammer or exposed to frost, plastic benefits due to price and the absence of the need for grounding. However, if we are talking about an input device in a private house on a pole or in a garage, metal becomes the uncontested leader. Pay attention to the “aging” parameter: many customers forget that transparent plastic doors on the street become cloudy after two years, making it impossible to visually monitor the condition of the machines without opening the panel.

The influence of climatic factors on the choice of enclosure

Russia has a huge variety of climatic zones, and what works in Sochi is categorically unacceptable for Yakutia. The temperature coefficient of expansion of materials plays a decisive role. Plastic has a high linear expansion coefficient. With sudden changes in temperature, characteristic of the off-season in the middle zone, plastic cases can “play,” which leads to a violation of the tightness of the joints and condensation getting inside. The metal also expands, but its structural rigidity compensates for these movements, maintaining the integrity of the seals.

Ultraviolet radiation is another hidden killer of plastic electrical panels. Even if the shield is installed under the visor, the reflected light can trigger the process of photodegradation of the polymer chains. We recommend using only enclosures with added UV stabilizers if installation is planned outdoors. Otherwise, after 3-4 years the lid may fall apart the first time you open it. Powder-coated metal boxes do not have this drawback, since the paint contains pigments that block the UV spectrum. However, here it is important to monitor the integrity of the layer: one deep scratch to the metal will become a source of rust, which will eat through the wall in a couple of years.

Humidity and chemically aggressive environments also dictate their own rules. In car washes, chemical laboratories or swimming pools, chlorine vapors and constant humidity quickly destroy cheap paint on metal. Here, specialized plastic boxes made of polypropylene or PVC show better chemical resistance. They do not rust and do not react to most reagents. But remember: such plastic often has a lower fire resistance class. Always check the certificate of conformity before purchasing.

Safety and standards: GOST, IEC and real practice

When purchasing equipment for industrial facilities or apartment buildings, you cannot rely only on the words of the seller. There are strict regulations governing the use of electrical installation products. In Russia, the main document is GOST R 51321.1 (complete low-voltage distribution and control devices). This standard is harmonized with international IEC 61439. It specifies requirements for strength, protection against electric shock and thermal conditions.

One of the critical points that installers often ignore is the flammability class of the housing material. Standards require materials used in electrical panels to withstand the glow wire test (GWIT) at 650°C or 850°C depending on the installation location. Cheap Chinese plastic boxes sold on construction markets without certificates often melt at 200°C. In the event of overload and fire inside such a shield, the housing itself becomes fuel, contributing to the rapid spread of fire along the wall. Metal panels, by definition, meet the most stringent fire safety requirements, since steel does not burn.

It is also worth mentioning the IP protection level (Ingress Protection). For a bathroom, the minimum acceptable is IP44, but we highly recommend IP65. Plastic boxes are easier to make airtight thanks to injection molding technology, where there are no welds. Metal panels are assembled from sheets, and the quality of sealing depends on the production culture and the quality of the sealing rubber. In our practice, there was a case when an expensive metal shield of a well-known brand leaked due to the fact that the factory forgot to glue the corner with a sealant. Water got into the differential switch, causing false alarms every half hour. Checking the tightness before installation is a mandatory procedure.

Grounding metal enclosures is a matter of life and death. If a phase breaks through to the body of the metal shield, and there is no grounding or has poor contact, the entire cabinet will be under 220V voltage. Touching such a surface is deadly. In this regard, plastic shields are safer for an unskilled user, since they are dielectrics. However, modern standards of PUE (Electrical Installation Rules) require grounding of any conductive parts, and if there are metal slats or locks in the plastic box, they must also be grounded.

Economic Analysis: Initial Price vs. Cost of Ownership

Many customers make the mistake of looking only at the price tag in the store. A plastic box with 12 modules costs on average 2–3 times less than its metal counterpart. The savings seem obvious. But let's calculate the total cost of ownership (TCO) over a 10-year horizon. Let's imagine a scenario for installing a shield in the entrance of an apartment building. The plastic box is susceptible to vandalism: it is easy to kick it or set it on fire. Replacing broken plastic will require new costs for materials and electrician work, plus downtime for the apartment’s power supply. The metal box, even if it receives a dent, will continue to function.

For industrial plants, equipment downtime due to electronic failure costs thousands of dollars per hour. The use of cheap plastic is unacceptable here. The reliability of a metal cabinet that protects expensive controllers and frequency converters pays off many times over. In addition, metal cabinets often have a better ventilation system and the ability to install additional accessories: heating fans, thermostats, large-capacity grounding bars. Plastic boxes are limited in their upgrade options: drilling an extra hole in a finished product is difficult and risky.

Another aspect is liquidity and recyclability. A good metal shield can be dismantled, repainted and used on another object. The plastic case, after dismantling, often has broken latches, a scratched surface and is considered a disposable product. For large-scale projects that require hundreds of panels, the difference in price is leveled out by the volume of the discount, and the issue of reliability comes to the fore.

Selection recommendations for different scenarios

Based on our experience and market analysis, we have formulated clear recommendations for different situations. Avoid universal advice “take what you like,” as compromises in electricity are dangerous.

• Apartments and residential buildings (indoor installation):Choose high-quality plastic boxes made from self-extinguishing ABS plastic. They are aesthetic, lightweight and safe. Make sure the door locks in the open position - this is critical for ease of installation. Avoid very cheap models with thin walls that sag when the screws are tightened.
• Private houses (street, facade):Only metal panels with powder painting and a degree of protection not lower than IP65. It is mandatory to have a visor over the shield, even if it has a high degree of protection. Consider heating the panel in winter so that condensation does not kill the automation.
• Garages, workshops, warehouses:Metal is preferred due to the risk of mechanical damage from tools or transport. If the room is dry and heated, a reinforced plastic box is acceptable, but metal is more reliable.
• Production workshops:Specialized metal cabinets (floor-mounted or wall-mounted) with a ventilation system. Plastic is prohibited due to the risk of static electricity buildup and low resistance to industrial pollutants.
• Wet areas (swimming pools, baths):Special plastic boxes made of polypropylene or stainless steel. Ordinary painted steel will quickly rust here, and ordinary plastic can become brittle from chemicals.

When choosing, pay attention to the brand. Well-known manufacturers (ABB, Schneider Electric, IEK, EKF) provide a guarantee for their products and comply with the technology. Unnamed boxes from markets often have mismatched sizes (the machines are difficult to enter or hang loose), which leads to poor contact and heating. Poor contact is the main cause of fires in electrical panels.

Typical errors during installation and operation

Even a correctly chosen box can be ruined by illiterate installation. One of the most common mistakes is violating the geometry of the housing during installation. If you screw a plastic box to a crooked wall “forcibly,” the housing will become deformed. As a result, the door stops closing tightly, the IP protection drops to zero, and dust accumulates inside. Metal panels are more tolerant of wall unevenness, but they cannot be installed skewed.

The second mistake is incorrect organization of cable entries. Often, installers simply break out the plugs with pliers, leaving sharp edges that cut the cable insulation. In metal shields this can result in a short circuit to the housing. It is necessary to use special oil seals or bushings. In plastic boxes, holes should be drilled carefully, removing burrs with a knife.

The third problem is the lack of labeling. There should be space inside the box for the connection diagram. Many plastic boxes have a transparent circuit insert behind the door, but users forget to put something in there. A year later, no one remembers which machine is responsible for what. In metal panels, the diagram is often glued to the inside of the door. This is a small thing that saves hours of troubleshooting in the future.

We encountered a situation where powerful switches were installed in a plastic box, generating a lot of heat. Plastic does not conduct heat well compared to metal. As a result, the machines began to heat up and operate prematurely (thermal protection). In such cases, you need to either choose a metal casing, or provide forced ventilation, or reduce the load on the line.

Final summary and selection strategy

A comparison of plastic and metal boxes for vending machines shows that there is no ideal material, there is only an optimal solution for a specific task. Plastic wins in ergonomics, price and dielectric properties for indoor projects. Metal has no alternative where vandal resistance, fire safety and operation in extreme conditions are important.

Our recommendation is simple: don't skimp on the case. The electrical panel is the heart of your power system and must be well protected. If your budget is limited, it is better to buy a smaller number of machines, but place them in a high-quality metal cabinet, than to fill them to capacity with cheap plastic. Remember that the cost of replacing burnt wiring or repairs after a fire is not comparable to the difference in price between a plastic and metal box.

Before purchasing, be sure to ask the supplier for a certificate of conformity and a product passport. Check the thickness of the metal (for metal panels) and the smell of the plastic (a strong chemical smell indicates low quality raw materials). If you are in doubt about the choice for a specific facility, consult with the project's chief energy engineer.

Professional solutions for complex industrial tasks

В то время как для бытовых нужд выбор часто сводится к балансу цены и эстетики, в тяжелой промышленности требования к оборудованию многократно возрастают. Здесь недостаточно просто защитить автоматы от пыли; необходима гарантия работы в условиях экстремальных температур, высокого давления и агрессивных химических сред. Именно в таких сегментах ключевую роль играют специализированные производители, такие какWuxi Kaisheng Electric Power and Petrochemical Equipment Co., Ltd..

Компания специализируется на разработке и производстве высокотехнологичного оборудования для энергетики и нефтехимии, где надежность металлических конструкций является критической. Хотя основной фокус ООО «Уси Кайшэн» направлен на создание теплообменного оборудования (титановые кожухотрубные теплообменники, аппараты ASME, воздушные охладители), их экспертиза в работе с материалами — углеродистой, нержавеющей и легированной сталью, титаном, медными и никелевыми сплавами — напрямую коррелирует с требованиями к промышленным электрощитам.

Продукция компании, сертифицированная по строгим международным стандартам PED и ASME, демонстрирует высочайшую коррозионную стойкость и способность выдерживать колоссальные нагрузки. Этот опыт создания компонентов для нефтепереработки, судостроения и опреснения морской воды подтверждает: когда речь идет о защите критической инфраструктуры, металл, обработанный по передовым технологиям, не имеет альтернатив. Подходы, применяемые «Уси Кайшэн» при изготовлении трубных решеток из нержавеющей стали 321 или сплавов N06625, являются эталоном качества, к которому должны стремиться и производители корпусов для ответственных промышленных электрощитовых.

Frequently Asked Questions

Можно ли использовать пластиковый бокс на улице?
Теоретически можно, если он имеет степень защиты IP65 и выполнен из УФ-стабилизированного поликарбоната. Однако мы категорически не рекомендуем это делат ь в климатических зонах с морозными зимами. Пластик становится хрупким на морозе и может лопнуть от снеговой нагрузки или града. Металлический щит с подогревом — единственное надежное решение для улицы в России.

Нужно ли заземлять пластиковый электрощит?
Сам корпус из пластика заземлять не нужно, так как он не проводит ток. Однако, если внутри щита установлена металлическая DIN-рейка, металлический замок или дверца с металлизированным покрытием, эти элементы должны быть заземлены согласно ПУЭ. Игнорирование этого правила создает риск поражения током при пробое изоляции.

Какой материал лучше защищает от пожара?
Metal definitely wins. Стальной корпус работает как огнеупорный барьер, сдерживая пламя внутри. Пластик, даже с добавками антипиренов, при длительном воздействии высоких температур разрушается, открывая доступ огню к окружающим материалам. Для объектов с высокими требованиями пожарной безопасности (школы, больницы, ТЦ) использование металлических щитов часто является обязательным требованием инспекторов.

Почему пластиковые боксы желтеют со временем?
Это процесс фотодеградации под воздействием ультрафиолетового спектра солнечного света. Дешевые сорта пластика начинают менять цвет уже через год. Качественные материалы с UV-фильтрами сохраняют белый цвет 5–7 лет, но на открытом солнце этот процесс неизбежен. Металлические щиты не желтеют, но могут выцветать, если использована некачественная краска.

Влияет ли материал бокса на температуру работы автоматов?
Да, влияет. Металл обладает высокой теплопроводностью и работает как радиатор, отводя излишнее тепло от автоматов, особенно при высоких нагрузках. Пластик является теплоизолятором. В плотно загруженном пластиковом боксе температура может быть на 5–10 градусов выше, чем в металлическом, что может привести к преждевременному срабатыванию тепловой защиты автоматов. При плотной компоновке в пластике необходимо делать запас по току автоматов (например, ставить 16А вместо расчетных 16А, если допускается, или 20А вместо 16А с учетом коэффициента).

Выбор правильного корпуса — это инвестиция в спокойствие. Мы готовы помочь вам подобрать оптимальное решение для вашего объекта, учитывая все нюансы эксплуатации.Изучите наш каталог электрощитового оборудования, чтобы ознакомиться с наличием сертифицированных моделей. Свяжитесь с нами сегодня для получения технической консультации и расчета стоимости заказа.