National Grid Electricity Distribution (NGED) has made the decision to standardise the fuse installed within domestic style cutouts to 80A.
Historically domestic and small commercial connections that have been provided to customers may have incorporated a cutout fused at 100A. This was deemed acceptable where the installation was terminated within an area where the temperature was less than 20°C during the peak demand period and where the earth fault loop impedance was no greater than 0.38 ohms. Although the fuse had a nominal rating of 100 amps, customers would seldom consume a power level near the maximum permitted and would typically have a much lower load.
However, with the inclusion of low carbon technology where the load profile is moving from ‘cyclic’ to ‘sustained’ and where the peak power consumption has moved from the winter to any season. NGED has made the decision to reduce the fuse size installed within domestic style cutouts to ensure that the current flow is restricted to within the thermal capacity of the installed equipment.
To read the policy, including our Q & A section, click here.