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Tom Christopher

Installing a 25mm 3core swa to feed an exisitng consumer unit due to the SEB moving the supply.

Planning to use a 100A 100mA time delayed rcd to feed the split load rcd board.

Sound ok?
 
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Dillb said:
Why would it need that? Nothing in BS7671 about it, and the DNO may not specify it.
Click to expand...
433.3.1 item (iii)
A device for Overload protection need not be provided at the origin of an installation where the distributor provided an overload device and agrees it affords overload protection to the part of the installation between the origin and main distribution point where further overload protection is provided.
The general consensus is that the DNO will allow 3 meters and no more for their cut out fuse to protect the tails.
Also 434.3
 
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Ian1981 said:
433.3.1 item (iii)
A device for Overload protection need not be provided at the origin of an installation where the distributor provided an overload device and agrees it affords overload protection to the part of the installation between the origin and main distribution point where further overload protection is provided.
The general consensus is that the DNO will allow 3 meters and no more for their cut out fuse to protect the tails.
Click to expand...
So as I say its speculation if its needed, nothing to say in this instance that the DNO require it fitting.
 
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My understanding is that the DNO will not generally allow their fuse to be used to protect any part of a consumer’s installation.
The 3m stipulation relates to the BS7671 requirement that overload protection must be provided within 3m of a reduction in the CCC of a conductor.
 
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This is northern powers requirements anyway
[ElectriciansForums.net] Submain Supply 100a 100mA
 
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Ian1981 said:
Why a 100mA S type rcd upfront?
Is it a TT system?
Will the dual rcd board accommodate a 25mm into the earth bar?
Will there be a switch fuse isolator fitted If the supply is over 3 meters from the cut out?
Click to expand...

PME

Yes dual board will take a 25mm

SWA will be made off into a metal enclosure with the 100a 100ma time delayed rcd. This will be mounted next to the main supply, so tails less than 3m

SWA will be above the plaster board so wont it need rcd protection?

I thought time delay to save both RCD trippings if there is a fault?
 
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spinlondon said:
My understanding is that the DNO will not generally allow their fuse to be used to protect any part of a consumer’s installation.
The 3m stipulation relates to the BS7671 requirement that overload protection must be provided within 3m of a reduction in the CCC of a conductor.
Click to expand...
Tho that is a regulation in the context you describe that has Nothing to do with the DNO tails
Read 433.3.1 and 434.3 or not
 
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Tom Christopher said:
PME

Yes dual board will take a 25mm

SWA will be made off into a metal enclosure with the 100a 100ma time delayed rcd. This will be mounted next to the main supply, so tails less than 3m

SWA will be above the plaster board so wont it need rcd protection?

I thought time delay to save both RCD trippings if there is a fault?
Click to expand...

There is no need for RCD protection for those reasons if using earthed SWA. If it did, then you RCD you selected would not have been suitable anyway.
 
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