Consumer unit change for 1st assessment

[mrmatt]

Hi all planning to do a consumer unit change for my first assessment. I know the configuration and board I am going to use however currently there is no main bonding and the current earthing cunductor from the service head is around 6mm in size and tails are 16mm. I was going to install 25mm tails and install an earth block to connect main bonding into,

The pictures below show the current service head. The earth cable goes directly into the current fuseboard. Obviously a 25mm cable will not fit into the termination on the service head.

Do i connect my 25mm earth cable to the earth block I install and into the consumer unit, and leave the current cable from the service head and connect to the block I install or is it best to upgrade this cable also to the largest that will fit in the service head?(or would you use 16mm)

Is it within the regs to leave a smaller size earth cable between my earth block and service head

Hope this makes sence

Thank Matt

 

[Johno]

The supply earth goes into your new earth block, and then you need to install a 16mm earth to your board.

I know that often the supply earth looks too small and shabby, but as long as you are getting satisfactory Ze results then don't worry about it.

 

[Guest123]

Why are you using 25mm earth???

 

[ezzzekiel]

25mm earth?

the earth between the supply and met is dno responsability, if there is no probs to change it then just upgrade, otherwise leave it for dno

 

[mrmatt]

Thanks guys, Ill be using 16mm earth got confused last night and was tired. (the tails i was looking at buying came as a set of 3 all 25mm)

is there anything else I need to be aware of for the assessment. I know there are many threads on here discussing such so Ill take a look in those also

Thanks for the replies

 

[nickblake]

What supply is it TNS or TNCS or is that earth going to the CDU ,supply appears to come from the bottom but the earth from the top ??

 

[mrmatt]

What supply is it TNS or TNCS or is that earth going to the CDU ,supply appears to come from the bottom but the earth from the top ??

i think its TNC-S its an old service head I believe that the newer ones have the earth connection in a sealed part. The unsheathed cable you see on the pic goes into the earth block on the old fuseboard.

 

[nickblake]

I thought it may have been then remove it when you change the board and replace it with a 16mm,earth
but before appling power to the new board ensure that you carry out a Zs test ,if this is for your assesment as im sure you have said, make sure all your bonding is in place Water gas oil etc that is a must take all the bonding to the earth block in the CDU

 

[mrmatt]

Havnt tried it yet but I have my doubts that a 16mm cable will fit into the hole? and this is the problem if it des not

 

[nickblake]

Im sure it will fit the holes are quite big

 

[SirKit Breaker]

Im sure it will fit the holes are quite big

Make sure you back the screw all the way out as well as the cable may be a tight fit, but as Nick states it should go in.