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Topic Title: Earthing Conductor Installation / High Zs
Topic Summary:
Created On: 21 January 2019 08:53 am
Status: Read Only
Linear : Threading : Single : Branch
 Earthing Conductor Installation / High Zs   - PWatts - 21 January 2019 08:53 am  
 Earthing Conductor Installation / High Zs   - AJJewsbury - 21 January 2019 12:20 pm  
 Earthing Conductor Installation / High Zs   - gkenyon - 21 January 2019 01:56 pm  
 Earthing Conductor Installation / High Zs   - chrispearson - 21 January 2019 01:59 pm  
 Earthing Conductor Installation / High Zs   - OMS - 21 January 2019 02:35 pm  
 Earthing Conductor Installation / High Zs   - PWatts - 21 January 2019 03:56 pm  
 Earthing Conductor Installation / High Zs   - Alcomax - 21 January 2019 04:21 pm  
 Earthing Conductor Installation / High Zs   - PWatts - 21 January 2019 04:24 pm  
 Earthing Conductor Installation / High Zs   - Alcomax - 21 January 2019 05:37 pm  
 Earthing Conductor Installation / High Zs   - chrispearson - 22 January 2019 09:48 am  
 Earthing Conductor Installation / High Zs   - AJJewsbury - 22 January 2019 11:01 am  
 Earthing Conductor Installation / High Zs   - mapj1 - 22 January 2019 11:06 am  
 Earthing Conductor Installation / High Zs   - John Peckham - 22 January 2019 11:06 am  
 Earthing Conductor Installation / High Zs   - PWatts - 22 January 2019 04:21 pm  
 Earthing Conductor Installation / High Zs   - mapj1 - 22 January 2019 04:27 pm  
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 21 January 2019 03:56 pm
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PWatts

Posts: 5
Joined: 05 June 2015

Many thanks for all of your replies.
It may well be that this Installation would never have achieved a 5s disconnection time , it was installed way before I began working here and was only recently picked up on an EICR .Any past Certificates cannot be found unfortunately so we are where we are and we need to rectify this installation as soon as we can .
The Ze at 0.03 ohms is low as the Main switch room sits adjacent to the main Incoming Transformer.
We have asked a local Contractor to assist us and are awaiting his findings. The underground joint which is a 120mm to a 185 mm is suspect and maybe breaking down with the Earth link across the Armouring.
I have contacted Schneider Technical a few times and they have assured me that a Zs reading of between 0.121 and 0.146 is required (depending on the short time setting of either 5 or 6).Yes this is very low so we have thought about fitting a Micrologic electronic Trip Unit if we can get one to fit in the enclosure as the existing MCCB is a Merlin Gerin Compact NS250 SX..
As such a low Zs is required I don't know if replacing the joint would help solve this and it would be difficult to cut it out and remake it anyway.
There are no Earthing Rings/Banjos or Earth fly leads at either end either but I am not sure that by fitting these (which we will be) will bring the Zs down to 0.121 ohms.
Just heard from the contractor and he is proposing 200 m of 120mm Earthing conductor .
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