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What is a MICC/Pyro Junction Box and MICC/Pyro cable?

What is a junction box?

A Junction BoxA junction box is metal enclosure housing electrical components, it serves as the communal destination connection for electrical wiring. The junction boxes protect the electrical connections from the weather elements, as well as preventing accidental electrical shock.Junction boxes form an integral part of an electrical circuit protection system especially in commercial buildings where fire proofing is a necessity to maintain emergency lighting or emergency power.

An MICC (Mineral Insulated Cable Co., Ltd) junction box carries out the same functions as normal junction boxes. The only difference is the internal connectors are designed to suit the different sizes of MICC (Mineral-insulated copper-clad cable) fire rated cables.

Micc - Junction Box For Mi Wiring CablesMineral-insulated copper-clad cables are a variety of electrical cables made from copper conductors inside a copper sheath, insulated by inorganic magnesium oxide powder. The name is often abbreviated to MICC or MI cable, and colloquially known as pyro. A similar product sheathed with metals other than copper is called mineral insulated metal sheathed (MIMS) cable, includes the junction box. The main function of MICC cable is to ensure that in the event of a fire that all the building emergency and essential circuits such as exit lighting, fire sensors, fire alarm circuits, service lifts, fire pumps and smoke extractors continue to function both during the building evacuation and the firefighting efforts.

It is the performance of the mineral insulated fireproof wiring cable which can provide this essential function.

Fire Survivival CableThe polymeric cables which are halogen-free, are typically made from polymers like polyethylene (PE & XLPE) because it is easy to process and cheap, however, although polyethylene is halogen-free it has a naturally high fire load and is thus likely to propagate flame. Secondly, materials like Polyethylene are commonly used as they are halogen-free; however, the burning Polyethylene will produce large amounts of carbon monoxide. Carbon monoxide is often claimed to be statistically responsible for most toxicity deaths in fires.

Plastic cable can overload due to short circuits or damage from falling objects which can generate further large amounts of smoke and toxic gases. As outlined in the NES713 standards, HCL toxicity levels 500ppm can cause fatalities. In addition, HCL corrodes expensive computer networks and equipment. Even low smoke halogen-free (LSHZ) cabling, after a few fire research institute investigations, show it is not much better than traditional cable.

The mineral insulated fireproof wiring cable which has been developed by experts at MICC is made from inorganic material eliminating the production of smoke and poisonous gas during a fire.  It also provides for an extremely mechanically strong cable that can withstand falling objects and water spray. In the environment which is full of heavy acrid smoke MICC fireproof wiring cable increases and enhances the chances that people will escape safely. It is suitable for underground constructions such as road tunnels, vehicle parking, and cable tunnels. It is also highly recommended and, in some cases, covered by local or national standards for installation in train stations, airports, docks, theaters and other high occupancy locations such as public buildings, art galleries and museums.

MICC mineral insulated (MI) cable is composed of inorganic material namely a copper conductor or conductors, mineral insulation-magnesium oxide (MgO) and the copper sheath. As stated in the IES228 standard, the melting point of the copper conductor and sheath is 1083 degrees Celsius. The melting point of the high purity MgO is 2800 degrees is Celsius. Mi cable will continue to function reliably in an environmental temperature up to 1000 degrees Celsius. This is the unique ability of MI wiring cable over that of the traditional wiring cable. There are different ways to manufacture Mineral Insulated cable. MICC use the Seamless tube technique as opposed to a welded tube, to ensure a totally flawless cable. The purpose of MI Cable is to act as the most durable cable on the planet for mission-critical applications. Seamless tube MICC cables have no inconsistency in the metallurgic structure of the tube and no risk of introduced contaminants as there is no welding. Thus, for these mission-critical applications, MICC seamless tube cables provide optimal lifetime security.

MICC MI cable is a standalone product, the product contains no polymer, uses no zinc, and does not require conduit protection. It is unaffected by the issues associated with cable-in-conduit systems and there have been no changes to the product that has consistently met the requirements for a two-hour fire resistive system when tested to UL2196 and ULC-S139 standards. The test UL2196 is consider by far the most realistic fire cable test in the world and is much more rigorous than any other test. The temperature is higher at 1020 deg C, the test is at full scale and required 5 samples both vertically and horizontal, water spray is with a firemen hose.

 The characteristics of the MICC/Pyro cable and Junctions:

Fire Safe Wiring SystemsFireproof: Mi cable will not burn, or support combustion.  By continuing to function when exposed to fire, it maintains vital emergency services.  The inorganic bare cable will not emit smoke, toxic gas propagate flame.

Wiring ad Cable and Conduit Combined: The cable sheath provides an excellent earthing medium and core protection, yet the overall diameter is smaller than other types of cables with equivalent current ratings and it is sufficiently pliable to permit intricate routing.

Pliable: MICC MI cable is fully annealed and as such is extremely malleable, enabling it to be easily bent to follow intricate shapes without detriment to its electrical characteristics.

Inherent Flameproof Barrier:  MICC MI cable has a solid construction with a non-flammable sheath.  The highly compacted insulation will resist the transmission of vapours, gases, or flames between items of equipment connected by the cable.

Mechanically Strong: The cable also withstands considerable abuse such as bending, flattening, and twisting, without electrical failure.  It is also resistant to rodent attack.

Non-Ageing: MICC MI cable is permanent and will not degrade with age as its sheath, conductors and insulation are for all practical purpose indestructible and completely stable. Hence the cable can be removed and re-used many years after initial installation, with subsequent savings in re-wiring cost.

High Corrosion Resistance: MICC MI cable, with its copper sheath, has a resistance to corrosion and for all normal environments need no additional protection. Where it may be exposed to chemicals specifically corrosive to copper, cables with an LSF protective outer covering are available.

Waterproof:  MICC MI Cable has a metal sheath which is impervious to water and gas.

Excellent Earth Continuity: The copper sheath eliminates the need for a separate circuit protective conductor. The excellent low resistance copper sheath conforms to the requirements of the IEE wiring Regulations (BS7671).

Radiation Resistance: MICC MI Cables are eminently suitable for installation in nuclear radiation environments because of their inorganic construction.

Zero Energy: Bare cable will not contribute to the energy of a fire.  A thin LSF outer covering offers minimal fuel to a fire situation.

MI With Small Overall Diameter: MICC MI cable have much smaller diameter than other types of cables with equivalent current ratings.  This ensures a neat installation with no deep chasing in walls.  A thin layer of plaster can accommodate the cable, or it can be run inconspicuously on the surface.

High Operating Temperature: Bare cooper sheath MICC MI Cables withstand continuous operating temperature up to 250 degrees Celsius, although the cable can be operated for periods up to temperatures approaching the melting point of copper (1083 degrees Celsius).

Competitive Installed Cost: MICC Cable eliminates the cost and potential structural damage caused by repair and replacement work associated with other cable types.  It also prevents the disruption to business operations through the need for building closure to allow such work to take place.

High Degree of Electrical Screening: The solid copper sheath of MICC MI Cables provide an excellent electrostatic screen. In addition, it also maximises electromagnetic compatibility (EMC), enabling the cable to be installed with minimum separation from other cables.  For specialised data communication applications, cable with twisted conductors is also available.


Pyrosales also sells the tools and accessories for installation of the MI Cable and Junction Boxes.

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