Fuse Boxes Selection Guide
Fuse boxes are divided into flush-mounted and surface-mounted; capacity is calculated from the total width of the devices on the rail, in 18 mm modules.
This guide covers the points to look at when choosing products in the Fuse Boxes category.
Fuse box types
- Flush-mounted box: the housing is recessed into the wall, and only the frame and cover remain on the surface.
- Surface-mounted box: screwed to the wall surface; the cables enter from the surface or through cable trunking.
- Sealed small boxes: Viko's single, 1-2 and 3-4 way surface-mounted models.
- Halogen-free housing: the abbreviation H.F in Viko product names indicates halogen-free material.
- Model with terminal block: one of the TP Elektrik flush-mounted boxes is listed as having a terminal block.
How to calculate the number of modules
The capacity of the box is the total width of the devices arranged side by side on the rail. According to DIN 43880, one module is 18 mm; the housing of a single-module device is 17,5-18 mm wide.
- List the devices to be fitted: the residual current device, one miniature circuit breaker for each circuit, and any other DIN rail devices such as a surge arrester and a timer relay.
- Add up the widths. A single-pole miniature circuit breaker is 1 module and a two-pole residual current device is 2 modules; the width of other devices is given in the manufacturer's data.
- Leave free space for circuits to be added later and choose the first capacity above the total.
Example: a two-pole residual current device and six single-pole miniature circuit breakers add up to 8 modules; an 8-way box would be completely full, and if spare space is wanted, a 12-way box is needed.
The devices are listed in the Miniature Circuit Breakers, Residual Current Devices and Miniature Circuit Breakers with Residual Current Protection categories. The number of circuits and fuse currents are determined in the project; for a preliminary assessment you can use the Current and Fuse Calculation from Active Power tool.
What IP 30 and IP 42 mean
The TP Elektrik boxes in this category are listed as IP 30 and IP 42. According to IEC 60529, IP 30 is a housing protected against objects larger than 2,5 mm and not protected against water. IP 42 indicates protection against objects larger than 1 mm and against vertically dripping water when the housing is tilted by 15°. Neither includes protection against splashing water or water jets.
Multi-row boxes and related categories
Plastic boxes with multiple rows and higher capacity are in the MCB Panels category; in product names they appear as ABS and PC housing with an opaque or transparent cover. Meter Boxes for meter mounting, and Panel Neutral Terminal Blocks and Panel Ground Terminal Blocks for the neutral and ground connections inside the box are separate categories; the compatibility of a terminal block with the box is verified from the manufacturer's data.
Brands in this category
- Viko: halogen-free flush-mounted and surface-mounted fuse boxes and sealed small surface-mounted boxes. In the Viko catalog the device rail is specified as galvanized sheet steel; the neutral and ground terminal blocks appear in the catalog under separate product codes.
- TP Elektrik: IP 30 surface-mounted and IP 42 flush-mounted MCB boxes.
Order notes
- Products are sold by the piece; fuses, residual current devices and other devices are not included with the box.
- For Viko products the number of modules and the mounting style are written in the product name (such as 12-Way Flush-Mounted); you can type this phrase into the search to find the product.
- TP Elektrik product names carry the stock code and the housing size (such as 3340-264-0400, 190x260).
- Most of the boxes in this category are made-to-order; the lead time is confirmed before the order.
Comparison and selection table
| Selection Criterion | Flush-Mount Fuse Box (2 – 36+ Modules) | Surface-Mount Fuse Box (1 – 36+ Modules) | Weatherproof (IP65) Enclosure Fuse Box |
|---|---|---|---|
| Mounting Method | Recessed into masonry wall or hollow drywall partition | Screwed directly onto wall, column or machine surface | Damp, dusty indoor rooms and outdoor weather-exposed walls |
| Module Capacity | 6, 8, 12, 16, 24, 36 DIN modules (1, 2 or 3 rows) | 1/2, 2/4, 6, 9, 12, 18, 24, 36 DIN modules | 4, 8, 12, 18, 24, 36 modules with sealing gasket |
| Door & Terminals | White or smoked transparent door, earth/neutral terminal bars | Clear or opaque hinged lid, pre-scored cable knockouts | Gasketed polycarbonate window, metric gland knockouts |
| Sizing Tip | Leave 20%–25% spare module space for future circuit expansion | Specify drywall-clip boxes for hollow gypsum walls | Mandatory for carports, gardens, wash bays & solar PV |
Frequently asked questions
How many modules should a fuse box for a home have?
There is no fixed number; the box is chosen according to the number of circuits in the project. Each single-pole miniature circuit breaker takes up 1 module, a two-pole residual current device 2 and a four-pole residual current device 4 modules. Add up these widths, leave free space for circuits to be added later and choose the first capacity above the total. The number of circuits and fuse currents are determined in the electrical project.
What is the difference between a flush-mounted and a surface-mounted fuse box?
The housing of a flush-mounted box is recessed into a cavity cut in the wall, and only the frame and cover remain on the surface; the cables come from inside the wall. A surface-mounted box is screwed to the wall surface and the cables enter from the surface or through cable trunking. The choice depends on whether the wall can be cut open and whether the installation is flush or surface. In this category both types are available in both Viko and TP Elektrik products.
What does H.F in a fuse box name mean?
H.F stands for halogen free. Halogen-free plastic does not contain halogen elements such as chlorine and, when it burns, does not release corrosive chlorinated gas as halogenated plastics do. Being halogen-free does not mean the box is non-combustible. The Viko flush-mounted and surface-mounted fuse boxes in this category are listed with the H.F designation in their product names.
Does a fuse box come with a rail and terminal blocks?
In the Viko catalog the device rail of the boxes is specified as galvanized sheet steel; the neutral and ground terminal blocks appear in the catalog under separate product codes. One of the TP Elektrik flush-mounted boxes is named as having a terminal block. Verify from the product page whether the neutral and ground terminal block is included with the product in the order; the miniature circuit breaker and residual current device are always purchased separately.