Discuss Earth Loop Impedance Table 17th Edition in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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WarrenG

Hi Guys,

Here is a handy 17th Edition Loop Impedance Table.

This table gives you a direct comparison with your Zs tests results and is calculated @ the 0.8 Rule of Thumb figure.

Enjoy! :)

Warren
 
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Hi Guys,

Here is a handy 17th Edition Loop Impedance Table.

This table gives you a direct comparison with your Zs tests results and is calculated @ the 0.8 Rule of Thumb figure.

Enjoy! :)

Warren


What do you mean by the 0.8 rule of thumb figure?? What is that??
 
DO you have to point 8 of your thumbs at something?? I've got 2 and am willing to lend tham out!
 
When taking a Zs reading, we cannot use the direct measurement to compare with the Zs earth loop tables in the Regs.

We have to take into account ambient temperature (at the time of test) and the conductor operating temperature. Both have an effect on the resistance. There is therefore a 0.8 rule to apply for your max Zs reading.

Example:

Regs book Page 49, Table 41.3, Type B BS EN 60898, 6A Zs = 7.67 ohms

7.67 x 0.8 Rule of Thumb = 6.13 ohms

17th Table - BS EN 60898, 6A Zs = 6.13 ohms

So the table gives you a direct comparison for your Zs readings.

Hope this helps!

Warren
 
OSG. The big one quotes the max allowed under perfect conditions then you have to adjust it by allowing for max operating temp etc. The 0.8 is allowing for worst case scenario but if your Zs is greater than the 0.8 adjusted figure it doesnt necessarily mean it has failed there are longer calcs that can be done to take into account each individual installation. Hope this is of use.
 
Warren

You posted a table with max eli details earlier this year. Im new to the forum, can you tell me how to get a hold of the table.

Cheers

Hugo
 
Thanks. I've got the tables in the Regs, but I thought that someone had taken the time to put them into another format; Word or Exel.

Just lazy mate!:)

Regards

Hugo
 
the tables in the on site guide and guidance note 3 give the values after the 0.8 calculation
bs 7671 gives the max before calculation
have a look on page 111 table b.4
osg page 103 table 2 d
for examples
 
Hi Guys,

Here is a handy 17th Edition Loop Impedance Table.

This table gives you a direct comparison with your Zs tests results and is calculated @ the 0.8 Rule of Thumb figure.

Enjoy! :)

Warren

where is it??
and does anybody have 100% values?
These 80% values are also in the NICEEIC test book
 
Just come across this post through a strange journey.

If anybody is using this table, please be aware that the BS3871 values in this table have been calculated at 240V and not 230V as is needed to conform with BS7671:2008.
 
A generator will not have a fixed earth, so whatever values you record will be much higher than is permitted. (see table in above post). However since it is on RCD, which of course is mandatory then is theory the values can be as high as 1766 ohms. Just record the values, and in the comment box state that it is a generator with an earth spike, thus giving high readings, but acceptable as is protected by an RCD.
 
When taking a Zs reading, we cannot use the direct measurement to compare with the Zs earth loop tables in the Regs.

We have to take into account ambient temperature (at the time of test) and the conductor operating temperature. Both have an effect on the resistance. There is therefore a 0.8 rule to apply for your max Zs reading.

Example:

Regs book Page 49, Table 41.3, Type B BS EN 60898, 6A Zs = 7.67 ohms

7.67 x 0.8 Rule of Thumb = 6.13 ohms

17th Table - BS EN 60898, 6A Zs = 6.13 ohms

So the table gives you a direct comparison for your Zs readings.

Hope this helps!

Warren

Am I right in saying that this is for an ambient temp of 10 deg C?

If so and the ambient temp at the time was 20 deg C then you could apply a correction factor of 1.04 to the OSG (0.8) figure. Then your Zs reading would have to meet the corrected figure.
 

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