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if you have an existing installation where the earth bar in C.U is being used as the MET( main bonds/main earth) and you now split the tails via henly/switchfuse to install a submain. is there anything stopping you splitting the main earth in a seperate MET then feeding the existing C.U. and switchfuse from the seperate MET making sure that CPC is sized correctly between MET and the C.U earth bar. i only ask as sometimes the mainbonds cannot be easily removed to connect to a single MET.
 

topquark

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Mentor
Arms
if you have an existing installation where the earth bar in C.U is being used as the MET( main bonds/main earth) and you now split the tails via henly/switchfuse to install a submain. is there anything stopping you splitting the main earth in a seperate MET then feeding the existing C.U. and switchfuse from the seperate MET making sure that CPC is sized correctly between MET and the C.U earth bar. i only ask as sometimes the mainbonds cannot be easily removed to connect to a single MET.
No, nothing stopping you doing that, but you should then connect the bonding to the new MET directly.

Have seen plenty that aren't like that though, where the CU is acting as an EMT (but also has final circuit CPC's connected). With careful placement of the new (external to CU) MET normally possible to do it properly.
 
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  • #3
yes totally agree, mainbonds should be in the MET,just sometimes the main bonds are buried and no slack to move. I guess its either move them to the new MET if possible or they will have to be re run.

sorry i misread your post re connect bonding directly to MET.
 
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  • #4
cant see another way as the the earth for the sub main can not be run from the existing MET ( C.U. earth bar) oh well least i know and can factor in future quotes.
 

ipf

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Separate MET (earth block) at the side of your Henleys, or wherever appropriate. Cut main earth and connect both ends into block. Options for other connections are then available, be they main earth or bonding.
 
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  • #6
been thinking . if the main earth is split via additional MET to earth a submain for example and then continues to main CU earthbar in 16mm which contains the main bonding conductors. is there really any electrical reason to move the main bonds to the new MET. i know the regs state that the main bonds should be run directly to the met but in reality what has changed by splitting the earth, i cant really see any problem as the bonding is connected to the new MET via the 16mm earth to the C.U. earth bar and the sub main earth is not reliant on the earthing to CU. not ideal but i cant think of a reason why as al connections are secure.
 

ipf

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See 411.3.1.2. It's how you read it IMO. 'Shall connect to the MET'. It doesn't say 'directly'. Unless there are difficulties, connect all to the MET. I may be wrong, but interpretation comes into it, again.
 
E

Engineer54

The external earth connection point will become your installations MET, and the CU(s) earth bar(s) your installations EMT(s). Frankly, for domestic CU's, i would Always choose to have the external earth connection point as my installations MET for all main earthing and bonding connections and leave the CU earthing bar (EMT) to look after the installations CPC's.

Apart from anything else, it makes isolation for testing purposes etc, far, far easier!!!
 
E

Edd

As your only installing a sub main and not installing the bonding then I would put it as a deviation on the EIC and leave it as is. As above though its how you read the reg. If I find it on a periodic I put C3, and put MET in CU as an observation. If theres slack then bring them to the MET, it will help your testing.
 
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ipf

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Mentor
Arms
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The external earth connection point will become your installations MET, and the CU(s) earth bar(s) your installations EMT(s). Frankly, for domestic CU's, i would Always choose to have the external earth connection point as my installations MET for all main earthing and bonding connections and leave the CU earthing bar (EMT) to look after the installations CPC's.
Me too, just mentioning the interpretation.
Apart from anything else, it makes isolation for testing purposes etc, far, far easier!!!
No doubt.
......
 
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