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Max Zs depending on mA of RCD. Ze/Ra then above 200Ohms is not considered stable by the regs and if you enquire the DNO normally state 21 Ohms for their electrode
 
Max Zs permitted is the maximum value that the OCPD need to trip. It is not the DNO value or the 200 ohm stable value.
There is no requirement for Zs to be of a value to operate the OCPD within the required time in the event of a fault to earth. The preferred means of earth fault protection on a TT is an RCD (411.5.2) and the maximum Zs value will be in accordance with table 41.5. (411.5.3).
The maximum value whether you like it or not is 1667 ohms for a 30ma RCD and that is the value to be recorded on a cert for a 30ma RCD.
 
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There is no requirement for Zs to be of a value to operate the OCPD within the required time in the event of a fault to earth. The preferred means of earth fault protection on a TT is an RCD (411.5.2) and the maximum Zs value will be in accordance with table 41.5. (411.5.3).
The maximum value whether you like it or not is 1667 ohms for a 30ma RCD and that is the value to be recorded on a cert for a 30ma RCD.

Yeah that is what I said ‍♂️
 
Just realised that this thread was about Zs not Ze or Ra..
My comment about the DNO figure of <200 was Ze..
 
If it helps the NICEIC online certification gives you 200 as the autofill value to select on their forms
 
I go by what the dno insist on and the only figure that is realistically acceptable <200

Which DNO insists on less than 200?
I've never heard of this before and considering the DNO have nothing to do with a consumers own earth electrode I don't see how it's any of their business getting involved?

If you enquire a DNO will give you a figure of 21ohms max for their side of things.
 
Which DNO insists on less than 200?
I've never heard of this before and considering the DNO have nothing to do with a consumers own earth electrode I don't see how it's any of their business getting involved?

If you enquire a DNO will give you a figure of 21ohms max for their side of things.

The Manx dno
 
Like Dave said it’s not their earthing connection, it’s upto the installer and the installer alone to determine the suitability of the electrode they install
 
I agree with the others saying winding a clamp on to it may have damaged their cable, they will want to take a look at that.
 

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