Domestic CU change and spurs off a ring main final

freedomrun · Aug 26, 2011

If i change a domestic CU and find that some of the socket outlets on a ring main final cct are unfused spurs or maybe unfused spurs from unfused spurs, and if the Zs complies at each s/o & IR test OK - can i leave as is ? or do i need to alter the spurs in the cct to comply with 17th edition.

daiplayer · Aug 26, 2011

max 1 socket on an unfused spur...... any more and you need to put a fuse in. ( to comply with regs)

freedomrun · Aug 26, 2011

Was connecting unfused spurs to unfused spurs on a ring final cct within a previous edition of the regs, if i'm changing a CU i do not have to bring the entire install up to 17th edition standards, i'm sure of that. Should i treat the ring final as a radial and use a lower rated protective device instead maybe.

daiplayer · Aug 26, 2011

Could be one way , cant see why not, downrating to a 20A treats those spurs as radials....protected i guess.

Not sure about it though, would be interested to see everyeone elses comments

daiplayer · Aug 26, 2011

freedomrun said:
Was connecting unfused spurs to unfused spurs on a ring final cct within a previous edition of the regs, if i'm changing a CU i do not have to bring the entire install up to 17th edition standards, i'm sure of that. Should i treat the ring final as a radial and use a lower rated protective device instead maybe.

Clarify something for me.....if im doing a csu change, deos the whole installation not need to meet 17th regs? ( for example for the nic domestic installer assessment ? )

nickblake · Aug 26, 2011

If you are doing a CU change then this work needs to be to current regulations ,and is notifiable , bonding to services gas water oil etc must be installed , and a full test and EIC certificate must be completed , with the installation you may find fault which also need rectifying ie the fused spurs as mentionedany work like this that has not been rectified should be noted on the certificate and customer advised , having said all that a PIR should have been carried out prior to the consumer unit change to identify any faults especially shared neutrals no cpc's in lighting circuits once this has been done the defects in the installation can be brought to the attention of the customer

freedomrun · Aug 26, 2011

With regrad only to the question of unfused spurs (i understand that when chaniging the CU any other defects in the installation must be highlighted to the customer + any immediate dangers isolated or corrected) - if the customer has an upgrade of Cu to the new edition - and unfused spurs are found all over the place and i as the installer are not able to place fcu to those unfused spurs (customer will not have it), can i leave as is if i downgrade the protective device (treat ring as a Radial) if all Zs comply at those s/o installed. Alternatively, if i do not do any work on the ring, can i make an observation that the unfused spurs were installed on the ring under a previous edition of the regs and i do not have to be retrospective an upgrade then to the new regs as the Zs complies to the cct protective device ??

Octopus · Aug 26, 2011

I'm not convinced you should be quoting for everything that you find is not up to the 17th edition. Sure make sure on the certificate that you note such non compliances with the 17th Edition.

IMHO If you locate a very "real" hazzard you need to highlight to the customer and fix.

I'm being very simplistic but to take a BS3036 and install a dual RCD 17th ed is a major safety step forward - this in its own right should make a home much safer!

Tin hat on.

Ponty Massive · Aug 26, 2011

Murdoch said:
I'm not convinced you should be quoting for everything that you find is not up to the 17th edition. Sure make sure on the certificate that you note such non compliances with the 17th Edition.

IMHO If you locate a very "real" hazzard you need to highlight to the customer and fix.

I'm being very simplistic but to take a BS3036 and install a dual RCD 17th ed is a major safety step forward - this in its own right should make a home much safer!

Tin hat on.

Spot on.

freedomrun · Aug 27, 2011

What about downrating ring to 20A and treating it as a Radial ??

tony mc · Aug 27, 2011

If the load on the final ring is ok for a 20 A mcb there is nothing to stop you doing this.

It would still be a final ring circuit not a radial.

Better still IMO split the circuit and place 2 x 20 A MCB in the CU but again depends on the load !

Agree with both Murdoch and Ponty re RCD protection and safer !!

Des 56 · Aug 27, 2011

I suppose that when you change a consumer unit you are making a decision on what size the protective devices are going to be, based on the type of circuit and the size of the conductors

Because something had a particular rating previously,it doesn't mean you just match that size

Each installation needs to have decisions made, and each installation will or may have different solutions
I dont think there is a one off, fit all answer

Deleted member 26818 · Aug 27, 2011

freedomrun said:
If i change a domestic CU and find that some of the socket outlets on a ring main final cct are unfused spurs or maybe unfused spurs from unfused spurs, and if the Zs complies at each s/o & IR test OK - can i leave as is ? or do i need to alter the spurs in the cct to comply with 17th edition.

No you don't have to upgrade the existing installation.
You would be expected to note any defects or non-compliances with the existing installation, in the section on the Certificate for comments on the existing installation.
If you did decide to make any alterations to the existing installation, such as splitting the RFC into two separate Radials, you would then have to ensure that such work complied with the current edition.

sparkinlee · Aug 27, 2011

I agree with the comments that a new board is safer than and old one, etc, but in my opinion you need to design the new board to provide proper protection for the cable configuration you know exists.

So I think you need either to provide FCUs for the spurs, or remove the spurs from spurs, or put the whole circuit on a 20A breaker, or (as has been suggested) reconfigure the circuit into 2 radials, or whatever is appropriate.