NYMJ are a type of cable that is PVC insulated, grey PVC sheathed, and 300/500 volt rated to BS EN 50265-2-1. The NYM cable is primarily used and is suitable for industrial or home applications. It is common to find the NYM-J cable placed in applications that are dry, moist, or wet open areas such as under plaster or in concrete.
NYM cable uses include for wiring inside buildings and they are available in single or multicore versions. At Meteor, you can find NYM-J cable options available in 3, 4, and 5 cores. The main difference between the NYY and NYM cable is that the latter includes NYMJ products with a copper core and single or more than one core cable that is shielded by an outer PVC sheathe.
An example of this is how the NYY-J cable and NYMJ cable use a green/yellow earthing or ground wire. In comparison, the NYM cable of the O variety and NYY-O cable doesn’t use that additional earthing cable.
What is NYM cable nomenclature?
NYM-J cable nomenclature has to do with the ampacity – the current carrying capacity of a NYMJ cable is known as its ampacity. This NYMJ property is unique for each wire or cable and is influenced by the conductor material of the NYM-J cable, number of conductors, and cross-sectional area. Thermal conductivity of the NYMJ cable and the thickness of its insulation are factors to be considered as well.
Can NYM-J Cables be Used in Outdoor Applications?
The NYM cable is known for its high level of durability and so can be laid outdoor in humid, dry or rainy environments. At the same time the NYM-J cable can also be implemented indoor in brickwork and concrete structures. The only types of installations that are not permitted for the NYM cable is under compressed, solidified reinforced concrete.
Is the NYMJ Cable Heat Resistant?
Insulated and sheathed in PVC, this cable has a voltage rating od 300/500V and the PVC insulation dictates a maximum conductor operating temperature of +70oC. However, the NYM cable can be used in installations where the temperature drops as low as -35oC.
More About NYMJ LSF Cables
LSF stands for Low Smoke & Fume and NYMJ LSF cables are primarily made up of a modified PVC compound which produces a lower amount of HCL gas and smoke on burning compared to PVC cables. Any NYM cable can produce 15% to 22% of HCL gas on burning but this depends on the quality of the NYM-J cable.
The PVC present in any NYM cable is modified to different degrees that are dependant on the manufacturer’s choice of additives. This means that the LSF NYMJ cables generally produce high volumes of dense black smoke and HCI emissions as well.
There is not much standard that can dictate what the emission differentials between LSF NYMJ cables and PVC cables should be. Some LSF NYM cable products produce 15% HCL while others can hike up to 24%.
The LSF NYMJ cables available for purchase at Meteor do contain halogen, so they should not be confused with Low Smoke Halogen Free (LSHF) cables. The percentage of PVC present in these cables differ depending on which manufacturer has made them, which is why installed LSF NYM cable products in public places becomes a type of lottery.
Some points to remember about NYMJ cables are that these are often purchased to cut cost and should be considered to have a significant improvement over PVC cables. In addition, LSF NYMJ cables are not recommended for public, large commercial buildings, near sensitive electronic equipment, and where escape is limited in case of fire.
