Type of service head

saucyjack · Aug 19, 2025

Hi guys. Could someone help me determine the original configuration of this service head? It is obviously single phase at the output, but did this start life as a three phase head that's been converted (for whatever reason) to single phase, or am i wide of the mark? Any advice appreciated!

westward10 · Aug 19, 2025

It is hard to say what is going on there. I suspect the cable earth at some point has broken down and one of the phases is now earth hence the link to the neutral. Why the other two phases go into a single fuse carrier is not clear maybe they are both now at the same potential. Only the DNO can say for sure.

James · Aug 19, 2025

That looks like a temporary lash up/bodge.
i would ask the dno to come and have a look at it.

littlespark · Aug 19, 2025

There’s been times in the past where a 4 core SWA has had cores doubled up to create a larger CSA for a single phase circuit…. but not on a DNO supply.

PS Electrics · Aug 19, 2025

westward10 said:
It is hard to say what is going on there. I suspect the cable earth at some point has broken down and one of the phases is now earth hence the link to the neutral. Why the other two phases go into a single fuse carrier is not clear maybe they are both now at the same potential. Only the DNO can say for sure.

Has the 3 phase cable been doubled up to provide a higher supply rating?

westward10 · Aug 20, 2025

PS Electrics said:
Has the 3 phase cable been doubled up to provide a higher supply rating?

Possibly, looks like it has been like that for years. The red ident disc is certainly old.

PS Electrics · Aug 20, 2025

littlespark said:
There’s been times in the past where a 4 core SWA has had cores doubled up to create a larger CSA for a single phase circuit…. but not on a DNO supply.

You learn something new every day Apparently this is called Bunching and is done on long runs to avoid Voltage Drop. Found it out in the following document

https://www.nationalgrid.co.uk/downloads-view-reciteme/652670

DNO need contacting that might be a fused Neutral in one leg?

saucyjack · Aug 20, 2025

Hi guys.
Thank you all for the replies; from what you all say it looks like the DNO could do with being involved at this point, particularly with the possibility of the fused neutral. Once again, cheers for al the help!