Minor works testing

[flameport]

However Anthony Hinsley in his book Testing Electrical Installations argues that you should disconnect the main equipotential bonding before an EFLI test.

That book should be burnt. Mr Hinsley has very strange ideas about testing, some of which would create dangerous situations.

 

[securespark]

PEB's should not be removed during EFLI testing, because they are normally connected when the installation is live and in use.

However, during a Ze test, the PEB's should be disconnected to allow an accurate measurement of the earth path via the main earthing conductor only. You don't want to include the parallel earth paths which may "artificially" reduce the Ze figure.

For example, I tested a TT-fed installation the other day. The Zs at a socket outlet was 0.34 Ohms.

However, when testing Ze with the PEB's disconnected, the reading was 224 Ohms.

Similarly, I tested a socket fed via a TN-S supply with a poor earth connection.

The Zs was 525, the Ze 1300 and something.

Makes a huge difference!

 

[ColJack]

I was tought that you disconnect the MEB from the CU to test the Ze, since just removing the PEB's still doesn't remove all the paths to earth such as bathroom bonding and such..

so the ony way to get a true Ze reading is to seperate the main earth from the system entirely...

 

[securespark]

I'm sure that's what I said...

 

[ColJack]

no, you said you remove the PEB's when testing the Ze..
no mention of removing the MEB from the MET...

and as I said that still leaves bathroom bonding in place and connected tot he MEB so you get paralel earth paths..

 

[Spark123]

Pop the means of earthing out of the MET and test to that, then it is in isolation.
(Remember to isolate the supply first!)