Eaton MEM HRC Fuse Selection:

In steady-load circuits, the HRC fuselink selected should be equal to - or slightly higher than - the amperage of the circuit: or of the apparatus being controlled, whichever is the lower.

Fluctuating-load circuits (e.g. - motor, capacitor or transformer circuits) are dealt with individually below.

Protection of Cables

Eaton fuselinks with gG characteristics protect cables against both overload and short circuit currents. The current rating of the fuselink (In) should be equal to or less than the current carrying capacity of the cable (Iz) when the circuit is protected by the fuselink alone.

Fuselinks may also be used for back up protection, for example in motor circuits, where the motor starter will provide the overload protection and the fuselink will provide short circuit protection. In this case, the maximum size of fuselink which can be used for cable protection depends upon the type of cable used and is calculated by the formula given in clause 434-03-03 of the Wiring Regulations (BS7671).

The table below shows the maximum fuselink rating for the two most common types of cable, 70°C PVC/copper (k=115) and 90°C thermosetting (XLPE)/copper (k=143).

Cable Protection Against Short Circuit Faults