How do I test an earth stake - please help!

[matt25]

Hi, I am not an electrician but desperatly need to know the basic guide on how to test an earth stake and what test equipment is required? I'd appreciate any response to be really basic, enough for a me to understand! Many thanks in advance.

 

[Liamsparks]

There are two different Methods for testing TT which I'll explain later when I'm sat at home. But please consider that testing is not easy and should be taken seriously therefore I suggest asking an electrician to do it. Because regarding which method of testing you choose a different tester is required.

 

[matt25]

Hi, I am simply trying to understand it bit will not be carring out myself! Trying to gain some knowledge so as not to have rings run around me.

 

[truckster]

Usual method is to use a Loop Tester which is connected to the phase and neutral at the consumer unit and the green/yellow cable connected to the stake. The reading is in ohms and should be below 200, the lower the better.

Alternatively you can use an earth electrode tester which is a long winded way of doing it, most sparks will use the loop tester.

 

[johnboy6083]

the easiest method is the EFLI method. it is exactly the same as taking a Ze measurement, using the earth rod, instaed of a suppliers earth. this method is only to be used on domestic TT systems.

For large premeises, the easiest method is the fall of potential method. Lenny posted a guide a while ago. ill try and find it

 

[matt25]

Thanks for the advice, much appreciated.

 

[malcolmsanford]

http://www.------.org/publishing/wiring-regulations/mag/2006/21-ttsystem.cfm?type=pdf

The above link was designed for the 16th edition but is a very good explanation of a TT and therefore how to test and Earth electrode.

 

[matt25]

Hi, thank you.

Would anyone have the patience to write a step by step guide please?

 

[richy3333]

Hi, thank you.

Would anyone have the patience to write a step by step guide please?

Everything you might want to know is in Guidance Note 8, Earthing and Bonding particularly for RA method, else measure Ze. You shouldn't undertake either test though, unless you know what you are doing

 

[Dean Williams]

just out of interest, why can't you use the Loop tester to test the electrode on an installation other than a domestic?

 

[johnboy6083]

it isnt very accurate. also because it says so in the OSG.

 

[topquark]

Hold one in each hand and wander the land. When the two cross over there's electricity beneath

 

[IQ Electrical]

just out of interest, why can't you use the Loop tester to test the electrode on an installation other than a domestic?

There is no specified building type for the loop tester method, the only stipulation is that the installation is protected by an RCD.

 

[richy3333]

it isnt very accurate. also because it says so in the OSG.

How so, and surely it's what BS7671 says that matters no the OSG?

 

[IQ Electrical]

How so, and surely it's what BS7671 says that matters no the OSG?

When you're measuring Ra values of around 100 Ohms as you are for most RCD protected TT systems then accuracy isn't quite so critical so the EFLI method is perfectly adequate.

If however, you're measuring Ra or Rb values for say a generator or transformer then accuracy is far more important so an earth electrode resistance tester is the instrument of choice (This is a common 2391-10 question).

 

[Geordie Spark]

Usual method is to use a Loop Tester which is connected to the phase and neutral at the consumer unit and the green/yellow cable connected to the stake. The reading is in ohms and should be below 200, the lower the better.

Alternatively you can use an earth electrode tester which is a long winded way of doing it, most sparks will use the loop tester.

Has anyone used a Metrel/Alphatek1557 mft for this?

If so, what setting do you use?

 

[Engineer54]

When you're measuring Ra values of around 100 Ohms as you are for most RCD protected TT systems then accuracy isn't quite so critical so the EFLI method is perfectly adequate.

If however, you're measuring Ra or Rb values for say a generator or transformer then accuracy is far more important so an earth electrode resistance tester is the instrument of choice (This is a common 2391-10 question).

And..... Don't forget Lightning Protection systems, need to use an earth electrode resistance tester here too!!!

 

[Engineer54]

Has anyone used a Metrel/Alphatek1557 mft for this?

If so, what setting do you use?

Like other MF Testers when used for earth rod testing using aux test electrodes, .... It's fine for domestic and light to medium commercial installations!!!