Electrical enclosure FAQs, answered by experts

The most recent regulations do not specify the maximum number of branch circuits allowed in panel-boards or distribution boards.

In the U.S., this limit is specified by the manufacturer and the information can be found in the data plate fine print, located on the inside of the enclosure door. In fact, the National Electrical Code (NEC) 2008 edition no longer sets a maximum number of overcurrent protective devices (OCPDs) that could be contained in a branch circuit panel. Therefore, it is possible to connect as many circuits as possible, as long as the maximum amperage per stab is not exceeded.

This differs from pre-2008 NEC regulations. These distinguished between lighting and appliance panel-boards, where the maximum number of OCPDs was set to 42, and power panel-boards, where more than 42 devices were allowed.

British standards differ slightly. BS7671:2018 does not state a maximum number of sockets-outlets that a ring or radial circuit can serve, similar to the NEC guidelines. However, it is important not to exceed the nominal rating of the OCPDs. As a result, while the number of BS1363-compliant socket-outlets shall be such that every portable luminaire and appliance can be fed from a conveniently accessible socket outlet, the floor area covered by a circuit is limited.

For example, a ring circuit protected by 30 to 32 ampere OCPDs and wired in 2.5 mm2 cables can have an unlimited number of socket outlets as long as the floor area served is not larger than 100 m2.

As a leading supplier and manufacturer of enclosures, Spelsberg can assist you in selecting the most suitable distribution boards that can accommodate the number of branch circuits you require. You can explore our complete offering here: https://www.spelsberg.co.uk/product-finder/

If your requirements are not satisfied by any of the solutions available, we are able to customise and supply specialist distribution boards that meet the specific needs of your intended application.

If you’d like more specific information about the maximum number of branch circuits in Spelsberg distribution boards or have specific needs, please feel free to send me a private message to discuss the best solution for your project.

It is very important to understand the properties of the equipment you are installing and how they will handle the local environment. For the majority of cases, the ambient temperatures will not affect the performance of a good quality enclosure, but the fact that you have asked this question probably means you are looking at a more specialist application.

There are four main plastic materials as well as three metals used in the manufacture of electrical enclosures and the properties of each one will determine the most appropriate choice.

Polystyrene enclosures offer a cost effective solution capable of operating between -25°C and 40°C. This temperature range also applies to ABS enclosures.

For situations that need a higher maximum temperature, polyester, or glass reinforced polyester (GRP) enclosures can withstand ambient temperatures up to 60°C. These products also offer excellent corrosion and chemical resistance.

For the widest range of operational temperatures, polycarbonate enclosures can be used in ambient temperatures between -35°C and 80°C. This premium material offers excellent resistance to impact as well as chemicals and corrosion.

If your requirements are not satisfied by a plastic enclosure, aluminium, mild steel and stainless steel should meet the demands of your application. Again, the temperature range for these is similar to polycarbonate with a minimum around -35°C and a maximum of approximately 75°C.

It is important to remember that many aspects of an application need to be considered when selecting an enclosure, including ingress protection rating, the surrounding environment and any pertinent standards or certifications.

Once you have identified the most suitable material, you can use the product finder on the Spelsberg website to filter by material type and make your selection process easier.

Further information on material choices can be found here: https://www.spelsberg.co.uk/…

Fastening an enclosure to a wall directly may affect its ingress protection (IP) rating if the wall or base of the unit is compromised. Therefore, if protection against dust and moisture is essential for the enclosure and its application, it is important to find a suitable fixing method that will not compromise the IP rating.

There are three main ways to securely attach an enclosure to the wall while maintaining the IP rating. They can be fastened by means of mounting plates, external feet or internal fixing positions.

It is possible to fit a mounting plate onto the wall before installing the enclosure. In this way, dust and water protections are maintained. Mountings incorporated into the enclosure structure are also available. These can be external, which completely separate the fixing positions from the body of the enclosure. Otherwise, the mounting points can be internal, but isolated from the wiring using grommets supplied with the enclosure.

All three are used throughout the Spelsberg range. For the internal mounting option, we provide cover screws that ensure maximum adherence to the enclosure, even when the device is mounted on a slanted surface, ensuring IP performance is maintained.

If you have specific questions about enclosure mountings for a project that you’re working on please feel free to send me a private message and I will help to identify the best enclosure for your needs.

For more information on IP ratings in different electrical enclosures visit https://www.spelsberg.co.uk/news/news-press/detail/ip-ratings-and-what-you-need-to-know/

A number of aspects need to be considered and accounted for when choosing electrical housings for precast concrete constructions. Firstly, the enclosures have to be resistant to leakage and prevent any ingress of concrete during pouring. Secondly, the housings should remain in a fixed position without moving. Strength and stability are also essential, so as not to compromise the integrity of the installation after the concrete has set. Finally, the electrical enclosures should be easy to install.

Currently, the only electrical housing solution specifically designed for use in precast concrete applications belongs to Spelsberg’s IBT series. The offering includes universal boxes, junction boxes, installation boxes, wall and ceiling transfers, special boxes and accessories such as sealing plugs, caps, blank bases, punch tools, cleats and support bars.

Thanks to its design, the IBT range is suitable for both prefabricated, precast concrete panels and cast-in-place concrete. The enclosures are fixed to metal or wooden formwork using magnets, epoxy or nails, and the interconnecting conduits are installed before pouring the concrete. When this is set, the formwork is taken off, and the face of the IBT housing is visible. As a result, on-site engineers can easily remove or drill through the face of the housing to gain access for cabling.

In this way, the solution from Spelsberg protects the electrical infrastructure from ingress by concrete and provides security of positioning, ease of assembly, simplicity of use on-site and a high-quality aesthetical finish.

For additional information on Spelsberg’s IBT enclosures, visit: https://www.spelsberg.co.uk/solutions/concrete-construction/overview/

If you have specific requirements for your intended precast concrete construction project, please feel free to send me a private message to discuss the solution that best fits your needs.

The most important aspect to consider when mounting a printed circuit board (PCB) into an enclosure is preserving the integrity of both the PCB and the enclosure. Failure to do so, e.g. drilling holes into the structures, could compromise the functioning of the PCB or affect the properties of the enclosures, e.g. IP rating, thermal resistance or impact protection. Therefore, pre-designed solutions are to be favoured.

Some manufacturers equip their enclosures with vertical guides within the side walls. However, this solution can result in the cable glands potentially fouling on the PCB once fitted through the side wall. Also, this design will often limit space within the enclosures, possibly blocking the entry for cables and other components.

Through many years’ experience working with electrical designers and installers, Spelsberg has addressed these issues by designing the PCB kit. This is installed in the corners of the enclosure, enabling cable gland entry and preventing any fouling effects.

The kit can be used on our TK range of polycarbonate (PC) and polystyrene (PS) enclosures, and is available in two variants, based on the size and design of the PCB. More precisely, for smaller applications we suggest using TK MLH-55/75, while we recommend using TK DST for larger PCBs and enclosures.

If you’d like more information about mounting PCBs into Spelsberg electrical enclosures or have specific requirements for your intended application, please feel free to send me a private message to discuss the solution that best fits your needs.

For TK MLH-55/75’s product specifications, visit: https://www.spelsberg.co.uk/industrial-housing/with-/-without-metric-knock-outs/19411001/