SPD for TPN 100a sub mains

sparky1888 · Dec 9, 2022

Hi Guys,

Looking for some options to provide surge protection to a 100a TPN sub main to be wired 60m from the origin

Im currently looking at installing a 4 way TPN mccb panel board with spd at the origin but it looks as if its going to cost the best part of a grand

This is obviously a far greater cost than installing a TPN 100a switch fuse but don’t really see many alternatives

Any one any ideas to keep the cost down?

pc1966 · Dec 9, 2022

Is there already some board at the source?

If it is simply a sub-main from supply point to the existing DB then just put in a switch-fuse for cable fault protection (assuming not TT!) at the source and then have the SPD at the end DB.

MCCB panels are expensive, and unless you get the fancy and expensive electronic MCCB (maybe with EL trip) they have a lower and harder to meet Zs requirement compared to the good old fuse.

If you absolutely have to have the SPD at the source then you could use a switch-fuse for the 100A over-current protection and then have a small DIN box for the SPD and a few Henley block to join it up, or some DIN terminals that can accept the size of incoming and outgoing wires as well as the link to SPD, or some line-taps in the DIN box, etc. Just keep the cables from block to SPD short (less then 25cm).

pc1966 · Dec 9, 2022

Just to add that the big Type 1+2 SPD often have double terminals and so are a junction as well as very short (low inductance) connection. For example: