Buried cables, RCDs, new CU.

[Lectrician]

Lets start a debate...

If you swap out a CU in a house, it's accepted it will be a dual split or RCBO type, offering 30mA protection to all circuits (exceptions here and there).

In a commercial, where do you stop?

For example, an existing 8 way TPN DB is fully loaded, having 24 single phase circuits, half a dozen with RCBO protection, as feeding sockets. You need to add more circuits. You could add a second 8 way DB adjacent, giving you another 24 single phase ways, and use these for your new circuits.

Or...

You could swap out the DB, because it was obsolete, damaged, or you just wanted one neat enclosure, with a 16 way TPN type, doubling you're capacity. Would you be obliged to install 30mA protection to every circuit where cables are buried in a wall? In many commercial installs, this could be all circuits....

 

[Spark123]

Personally I just wouldn't want the agro of the C3 on the next EICR and the customer complaining of it only being replaced not long ago, so bring it up to regs.

 

[flameport]

Would you be obliged to install 30mA protection to every circuit where cables are buried in a wall? In many commercial installs, this could be all circuits....

Yes, as the options are either do that and complete the certificate stating it complies with BS7671 - or not, and then the certificate can't be completed as the installation will not comply.

 

[JohnW2]

Yes, as the options are either do that and complete the certificate stating it complies with BS7671 - or not, and then the certificate can't be completed as the installation will not comply.

What certificate are you talking about - an EIC? If so, surely the work (being certified) can comply with current regs, even if the installation doesn't.

... unless, that is, you're thinking of the requirement for RCD protection of buried cables as being a 'DB issue' rather than a 'cable issue'. The impression I get is that most people regard it as the latter - such that they do not consider it to be non-compliant, per se, to install a DB which does not give the protection to buried cables that would be necessary for the cables to be compliant with current regs.

Kind Regards, John

 

[leckie12]

It's down to the extent of the work being covered by the EIC. What would you describe the work being done as covering? If for example you are replacing a DB you are not required to tick boxes relating to the routing of cables in correct zones, it would be NA. You have installed a new DB and protective devices, you fill in the schedules that relate to that only. If you have fitted an RCBO or an RCD that gives additional protection to a circuit then you can tick the box because it relates to part of the work you have carried out. Although you might prefer to fit an RCBO into a TPN board to protect buried cables, if the client doesn't want to "improve" their installation you cannot make them, but you could comment on the existing installation.

 

[JohnW2]

It's down to the extent of the work being covered by the EIC. What would you describe the work being done as covering? If for example you are replacing a DB you are not required to tick boxes relating to the routing of cables in correct zones, it would be NA.

That was, of course, exactly my point.

Kind Regards, John

 

[leckie12]

Indeed John, I was just expanding the point for the OP

 

[Lectrician]

That's the way I see it too. There is a good practice guide for domestic installs, which bangs on about being permitted to swap out a CU if the lights have no earth if a sticker is placed on the board, but it also says all circuits must comply to BS7671. Contradiction.

I think if I approached the NIC for an answer, they would cover their backs and say you need to install RCBO protection to all circuits.

 

[JohnW2]

That's the way I see it too. ... I think if I approached the NIC for an answer, they would cover their backs and say you need to install RCBO protection to all circuits.

They might well say that, and for the reason you suggest. but where (if anywhere!) does that process stop. Would they suggest that every aspect of every final circuit had to be fully compliant with current regs in order for a CU change to be certifiable as 'compliant'?? If they really wanted to be silly, I suppose they could even say that 'old colours cable' in any of the final circuits renders the CU change 'non-compliant'!

Kind Regards, John

 

[leckie12]

lectrician, have a read of items 1.2, 3.1 and 3.2 of BPG1.

Think why you are replacing the board. in your example you are replacing it in order to increase the quantity of available circuit ways. Your are intending to reconnect existing circuits plus add others. If the additional circuits are new then they obviously need to comply fully with the current versions of BS7671. You have no obligation to upgrade the existing circuits to the latest standard although you may advise your client to improve their installation to the latest standard. The same advice you are giving by giving a C3 code if carrying out an EICR. However, you must not leave the installation in a worse condition that it was prior to the alteration. So if the existing MCB's were say type BS3871 30A type B and you were replacing with a 32A BS 60898 type B, the max EFLI of the new device is lower than the previous device and you would need to ensure that the device would still operate within the prescribed time. So that is an example of the alteration you would make possibly having an effect on the safety of the existing installation. However, your alteration would make no difference to the safety of a cable buried in a wall.

So if you rang the NICEIC or similar, they may suggest you explain the benefits of fitting an RCD for additional protection for existing cables buried in the wall, but they would not insist on it.

 

[leckie12]

If you are swapping a DB, the best advice is to carry out an EICR prior to the replacement. If there are any C2 or C1 codes they should be addressed of course.

 

[Adam_151]

At the end of the day, I cannot really see anyone able to say you're doing is wrong as long as the installation is no less compliant with 7671 than before*. As to Spark123s concern, perhaps if there is someone from the client who understands what you are telling them..... then price it both ways and give them the choice of whether to go for the extra RCBOs or not, document their decision on the scope of works on the EIC.



*say for example, 15th edition install, a DI has come along and slapped an RCD main switch in the board and it keeps going out and you are replacing the board to put RCBOs on the sockets, You'd not be came to justify leaving other circuits with concealed cables not on RCD as they were RCD protected prior to you starting work

 

[Risteard]

I certainly wouldn't argue that if a protective device is being replaced that it shouldn't be one which would provide necessary protection for whatever reason.

So if replacing a distribution board it would be unwise not to add the RCD protection and if something happened few would stand up for you.

 

[Risteard]

At the end of the day, I cannot really see anyone able to say you're doing is wrong as long as the installation is no less compliant with 7671 than before*.

New work must comply with BS 7671. There is no provision for work simply not being less compliant than before.

 

[EFLImpudence]

The new work is replacing a distribution board; is there a regulation which states that distribution boards, new or otherwise, must contain RCDs?