Can a SPD be installed in a domestic installation without an earth conductor connecting it to the MET, because it will discharge the surge from the live line conductor to the neutral conductor?
That setup has a cable length from the N-E link at the cut out to the CU of about 1m, and the length of the SPD leads to the CU is about 0.5m. So...
That model of SPD reduces transients across its L-N terminals to about 1kV. That means it reduces transients across L-N at the CU to 1kV plus inductance from 0.5m x 2 of cable; and reduces the transient across L-E at the CU to 1kV plus inductance from 1m of SPD cable, plus 1m N CU-to-link cable and 1m E CU-to-link cable. The BEAMA guide to SPDs implies that you can easily add another 1kV per m of cable, so devices downstream of the CU may see L-E transients only reduced to 4kV.
Having said that, the E SPD connection isn't required for the L-N part of its functionality to work.
That setup has a cable length from the N-E link at the cut out to the CU of about 1m, and the length of the SPD leads to the CU is about 0.5m. So...
That model of SPD reduces transients across its L-N terminals to about 1kV. That means it reduces transients across L-N at the CU to 1kV plus inductance from 0.5m x 2 of cable; and reduces the transient across L-E at the CU to 1kV plus inductance from 1m of SPD cable, plus 1m N CU-to-link cable and 1m E CU-to-link cable. The BEAMA guide to SPDs implies that you can easily add another 1kV per m of cable, so devices downstream of the CU may see L-E transients only reduced to 4kV.
Having said that, the E SPD connection isn't required for the L-N part of its functionality to work.
