The Service Head

Thanks for taking the time to read this article, I’m sure you will find something in the content that will help keep you safe. My name is Chris Hector I’m a registered Approved Contractor with the NICEIC, (the UK’s leading voluntary regulatory body for electrical contractors).  The service head is where the electrical supply enters your property, runs through the main cut out fuse and continues on to your meter.  Here is an example of a service head.

service head

This is the most dangerous part of your system.  Fault currents could potentially reach into the 1000’s of Amps, more than enough to start a fire or kill someone.  As such it’s not really something you should be poking around at, but here are some simple visual checks you can make.

  • Is the service cable marked, scratched or damaged.
  • Is the service head cracked or showing signs of thermal damage.
  • Is the service head safely secured to a wall.

Here is an example of a dangerous service head I found in Nottingham.  The mounting board has disintegrated so the service head is only supported by the cables.  The casing is broken exposing the copper of the neutral wire.

dangerous service head

I called Western Power, Distribution Network Operator in my area, (DNO) and they responded within a couple of hours to solve this dangerous situation.  They removed the broken service head fitted a new mounting board and fully replaced the service head.

new mounting board and fully replaced service head

WARNING: BONDING CLAMPS

Sometimes the lead sheath of the service cable is used to earth your system.  This is perfectly acceptable if the connection is made correctly and the test results meet the required standards.

service cable used to earth your system

Bonding clamps should not be attached to the service cable as can be seen opposite.

Bonding clamps are used on copper water and gas pipes.  They aren’t appropriate for the lead sheathing of the service cable.  The locking screw can be forced through the lead sheathing and penetrate the cable creating potential fault currents into the 1000’s of amps.  More than enough to start a fire or kill someone.

If you see a bonding clamp on your service cable DO NOT TOUCH IT.

Bonding clamps used on copper water and gas pipes

Here is a picture showing the damage a bonding clamp can do.  In the centre of the rectangle the lead sheathing has been split and the yellow paper wrap is visible.  This is the last layer before you get to the live and neutral cables.  A lucky escape for whoever tightened this up and the Nottingham landlord.  Western power had to dig up the pavement and replace the cable.

picture showing the damage a bonding clamp can do

If you have any of the above issues and you are in my area you should call Western Power and inform them of your concerns (0800 096 3080). If you are not sure give me a ring and I'd be happy to professionally inspect the service head for you.

If you are elsewhere in the country you can look up your DNO on the below link: