SELECTION OF MAINS SPDs to BS:EN 62305

Three Phase Systems

Earthing System
Lightning Protection Level (LPL)
Main Distribution Board (MDB)
Sub-Distribution Board (SDB) (unless feeding outside circuits) (figure given is cable length, not distance)
Electronic Equipment (less than 5m cable length)
TN-C
I & II
KM1+2-25-3+0 SC
KM2-20-3+0 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-3+0 SC (>50m from MDB)
KM1+2-25-3+0 SC (>100m from MDB)
TN-C
III & IV
KM1+2-12.5-3+0 SC
KM2-20-3+0 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-3+0 SC (>50m from MDB)
TN-S
I & II
KM1+2-25-4+0 SC
KM2-20-4+0 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-4+0 SC (>50m from MDB)
KM1+2-25-4+0 SC (>100m from MDB)
TN-S
III & IV
KM1+2-12.5-4+0 SC
KM2-20-4+0 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-4+0 SC (>50m from MDB)
TN-C-S
I & II
KM1+2-25-4+0 SC
KM2-20-4+0 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-4+0 SC (>50m from MDB)
KM1+2-25-4+0 SC (>100m from MDB)
TN-C-S
III & IV
KM1+2-12.5-4+0 SC
KM2-20-4+0 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-4+0 SC (>50m from MDB)
TT
I & II
KM1+2-25-3+1 SC
KM2-20-3+1 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-3+1 SC (>50m from MDB)
KM1+2-25-3+1 SC (>100m from MDB)
TT
III & IV
KM1+2-12.5-3+1 SC
KM2-20-3+1 SC (>10m from MDB)
KM3-10-3+1 SC
KM1+2-12.5-3+1 SC (>50m from MDB)

Single Phase Systems

Earthing System
Lightning Protection Level (LPL)
Main Distribution Board (MDB)
Sub-Distribution Board (SDB) (unless feeding outside circuits) (figure given is cable length, not distance)
Electronic Equipment (less than 5m cable length)
TN-C
I & II
KM1+2-25-1+0 SC
KM2-20-1+0 SC (>10m from MDB)
KM3-10-1+1 SC
KM3-275-A
KM1+2-12.5-1+0 SC (>50m from MDB)
KM1+2-25-1+0 SC (>100m from MDB)
TN-C
III & IV
KM1+2-12.5-1+0 SC
KM2-20-1+0 SC (>10m from MDB)
KM3-10-1+1 SC
KM3-275-A
KM1+2-12.5-1+0 SC (>50m from MDB)
TN-S
I & II
KM1+2-25-2+0 SC
KM2-20-2+0 SC (>10m from MDB)
KM3-10-1+1 SC
KM3-275-A
KM1+2-12.5-2+0 SC (>50m from MDB)
KM1+2-25-2+0 SC (>100m from MDB)
TN-S
III & IV
KM1+2-12.5-2+0 SC
KM2-20-2+0 SC (>10m from MDB)
KM3-10-1+1 SC
KM3-275-A
KM1+2-12.5-2+0 SC (>50m from MDB)
TN-C-S
I & II
KM1+2-25-2+0 SC
KM2-20-2+0 SC (>10m from MDB)
KM3-10-1+1 SC
KM3-275-A
KM1+2-12.5-2+0 SC (>50m from MDB)
KM1+2-25-2+0 SC (>100m from MDB)
TN-C-S
III & IV
KM1+2-12.5-2+0 SC
KM2-20-2+0 SC (>10m from MDB)
KM3-10-1+1 SC
KM3-275-A
KM1+2-12.5-2+0 SC (>50m from MDB)
TT
I & II
KM1+2-25-1+1 SC
KM2-20-1+1 SC (>10m from MDB)
KM3-10-1+1 SC
KM1+2-12.5-1+1 SC (>50m from MDB)
KM1+2-25-1+1 SC (>100m from MDB)
TT
III & IV
KM1+2-12.5-1+1 SC
KM2-20-1+1 SC (>10m from MDB)
KM3-10-1+1 SC
KM1+2-12.5-1+1 SC (>50m from MDB)