When planning to electrify your home or replace your old equipment, you inevitably face the question of choosing the right housing for metering devices. Electricity meter shield It is not just a plastic box, but the first link in the chain of security of your home. It is from its quality, tightness and proper configuration that the durability of expensive equipment and protection against electric shock depends.
Property owners often underestimate the importance of this element by choosing a cheapest option or relying on chance. However, PUE (Rules of electrical installations) They dictate strict requirements for the installation site and the execution of the cabinet. Incorrect choice of material or class of protection can lead to failure of electronics due to moisture or, worse, to a fire situation.
In this article we will discuss in detail what distinguishes street and interior boxes, how to correctly calculate the place for machines and what energy sales company requires when filling. A well-assembled node of accounting is calm for years to come and no problems with the regulatory authorities.
Classification of electric shields: material and purpose
The main separation of shields occurs according to the material of manufacture of the case and the intended installation site. Metal products are traditionally considered more reliable in terms of vandal protection and fire safety. Plastic (polycarbonate or ABS plastic) benefits in weight, dielectric properties and corrosion resistance, but may be less resistant to mechanical damage when impacted.
For internal installation in residential buildings and apartments, plastic boxes are most often used. They are aesthetic, easy to install and do not require grounding of the case (although a metal mounting panel inside is mandatory). Metal shields They are more often used in industrial buildings, garages or where there is a high risk of physical exposure to equipment.
If you plan to install on the street, the choice is narrowed to specialized sealed models. The protection class is critical. IP. For the street, the minimum permissible is considered to be IP54but it is better to be guided by IP65 and higher. Such housings are equipped with seals around the perimeter of the door and plugs for inlet holes.
⚠️ Note: The use of a conventional apartment shield on the street is strictly prohibited. Even under the canopy, humidity and temperature changes will cause condensation, which will lead to a short circuit.
Also, it is worth considering the type of installation: invoice or built-in. Embedded models save space in the corridor, but require a niche in the wall, which is not always possible in concrete floors. Overheads are universal and are attached directly to the surface of the wall or DIN-rail inside the cabinet.
Requirements for street boxes and protection classes
Installing a metering unit outdoors is always a challenge for the equipment. Street shield It must withstand extreme temperatures, ultraviolet radiation and direct water intrusion. Manufacturers use special additives in plastic or powder anti-corrosion coatings for metal to extend the life of the product.
The key parameter here is the protection class. IP. The first number indicates protection from solid objects, the second - from moisture. For the street, the second digit should be at least 4, and preferably 5 or 6. This ensures that water jets or heavy snow do not penetrate inside the live parts.
Particular attention should be paid to the temperature regime. Standard plastic shields can become brittle in the cold below -20°C. For harsh climates, there are special frost-resistant modifications made of polycarbonate, retaining properties up to -40 ° C and even below.
An important element of street boxing is the observation window. It allows the meter to be taken without opening the door and breaking the seal. The window should be made of durable, not cloudy with time material.
The layout and internal filling of the shield
Choosing a body, you need to think in advance of its "stuffing". A counter shield is a modular system where all elements are attached to a DIN rail. The standard width of one module (single-pole machine) is 18 mm. You need to provide space not only for the meter itself, but also for the input machine, protective shutdown devices (see below).CCD) and escaping machine guns.
A typical connection scheme requires the installation of an input machine in front of the meter for the possibility of safe replacement of the meter. After the meter is usually put a general RCD or differential machine, protecting all the wiring in the house. Next are the machines for the rosette groups and lighting.
☑️ Checking the configuration of the shield
Don’t forget to organize the space for the wires. Cross modules or switchboards should be installed inside the shield to carefully dilute phases and zeros. The chaotic bundle of wires is not only ugly, but also makes it difficult to maintain and cool appliances.
Direct-on meters often require additional expansion modules or special seats, as the dimensions of modern electronic meters may differ from standard modular dimensions.
Table: Comparison of popular shield models
To simplify the choice, consider the comparative characteristics of several typical market representatives. These parameters will help determine which one powershield It is suitable for your specific operating conditions.
| Model/Type | Materials | IP Protection Class | Number of modules | Features |
|---|---|---|---|---|
| ABB Mistral 41 | Plastic. | IP65 | 18-72 | Removable frame, transparent door |
| IEK KMPN | Metal | IP31 | 12-36 | Budgetary, for premises |
| Schneider Kaedra | Plastic. | IP65 | 12-54 | High impact resistance |
| Street. boxing | Metal/Plastic | IP54 | Under the counter | Window, lock, hinged |
When choosing, pay attention to the presence of DIN-rails in the kit. In cheap models, it may be absent or too short, which will require the purchase of additional accessories. Also important is the possibility of installing a second internal door for filling the introductory machine.
Why do you need a second door in the shield?
The second internal door (or curtain) is necessary so that the energy sales company can seal the input machine and the meter, leaving access to the remaining machines (exhaust lines) open to the user. This allows you to turn on/off the lights in your home without calling an inspector.
Rules for installation and sealing
Installation of the shield is a process that requires strict compliance with the norms. Before starting work, electricity must be turned off. The height of the meter installation is usually regulated from 0.8 to 1.7 meters from the floor for ease of taking readings. The fastening should be rigid, eliminating vibration.
Particular attention is paid to introductory holes. In street shields, they should be tightly closed with plugs. The cable is inserted through special sealed inputs (seals) to exclude moisture from the cable shell inside the housing.
⚠️ Warning: Before the final tightening of all connections and closing the covers, make sure that access to the terminals of the counter and introductory machine allows you to install seals. If the seal cannot be put, the energy sales will refuse acceptance.
To connect, use only a copper wire with a section corresponding to the load (usually at least 10 mm2 for entering the house). The ends of the wires should be pressed with tips or carefully serviced, especially if screw clips are used.
Security and Typical Errors
The most common mistake is saving on the protection class. Installation of a shield with IP31 It is guaranteed to cause problems in one or two seasons. Moisture condenses inside, oxidizes contacts and can cause an arc break.
The second mistake is overheating. If the shield is metal and is standing in the sun, it can heat up to high temperatures. This affects the accuracy of the electronic counter and heat disengagement machines. It is critical to install shields in shaded areas or use visors.
The third problem is the lack of stock on modules. Often when buying a shield "back-to-back" forget that additional devices may be needed: voltage relays, power limiters or ultrasound. As a result, you have to change the entire building or make "kolkhoz" extensions.
Properly selected and installed shield is a guarantee that your accounting system will last the entire interval without failures and penalties from power companies.
Frequently Asked Questions (FAQ)
Can I install the counter on my own?
Technically, any person with electrical installation skills can install the case and connect the wires. However, the introductory machine and the meter itself must be sealed by a representative of the energy sales company. Unauthorized violation of the seal entails heavy fines. Therefore, if you change the shield completely, it is better to coordinate the work with your energy supplier.
How high is the street shield to be installed?
According to the PUE, the height of the installation should provide convenient access for taking readings. This is usually a range of 0.8 to 1.7 meters. If the shield hangs on the support, often make two tiers: the upper for the counter (inaccessible without stairs, but visible), the lower for automatic machines, or use telescopic racks.
Do I need to ground a metal shield?
Yes, metal housings of electrical installations must be grounded. This protects a person from electric shock in the event of a phase breakdown on the body. To do this, there is a grounding terminal on the inner wall of the shield, to which the PE conductor is connected.
What to do if there is condensation in the shield?
The appearance of condensate indicates insufficient tightness or a sharp temperature drop. The integrity of seals, plugs and glands must be checked. In some cases, it helps to install a special heater for electric panels, which is turned on automatically at low temperature and high humidity.