periodic certification requirements on 16th edition consumer unit

[millymolly35]

Hi, I need some help and this is my first time on here so please forgive me if this question has been repeated many times. Im looking to convert my house and let rooms individually so need to have some mains wired smoke and heat detectors installed and a periodic check, however ive had various conflicting informaiton about my consumer unit. I currently have a 16th edition time delayed split hager board, with one RCD that is 240 V 100Ma, this is on a TT earthing system. I have been told by one electrician that I need a new consumer unit as the RCD is obsolete and cannot be replaced and that I need to get the Ma down to 30Ma. However ive also been told by another electrician that I will be wasting my money as they will be replacing it with the same board, as a TT earth requires a 100MA incomer ?? and that the current conusmer unit will just show a mark 4 requirement on my periodical. As an alternative it has been suggested to use a RCBO to cover the switches that are currently protected off the 100Ma RCD, I have two blanks available on the board, but dont know if this is enough. Any help would be massively appreciated as its taken me ages to understand the little bit I have so far.
Thanks

 

[Sintra]

Ok if you are getting work done then only the circuits that are being installed or modified need to be compliant to the 17th edition. So if you are having to get the consumer unit changed to allow for modifications then it needs to be installed to the 17th edition and an EIC issued.

If for example you were only getting a periodic report done on the existing installation then even your socket outlets do not comply to the 16th edition as these needed to be protected by a 30mA RCD on a TT system. The 100mA RCD would surfice for the lighting and and other non socket circuits.

 

[millymolly35]

Sintra thanks, the only work im having done is the installation of the mains wired smoke and heat detectors which I understand run off the lights anyway, these are two of the circuits which are on the 100Ma I also have two blanks on that side and an emmersion circuit, although we no longer actually have an emersion heater so im assuming that is not required. All the socket circuits run off the other side which is a 30Ma, so from what your saying as these are already at a sufficient level the consumer unit in itself is fine ?? and an RCBO for the lights would just give extra protection but its not essential ??
Thank you

 

[Sintra]

Right got the drift now, if you add the smoke detectors to the lighting circuit then this addition needs to comply to the 17th.
There are a few ways to achieve this.
1. Move the lighting circuit onto the side of the consumer unit protected by the 30mA RCD.
2. Leave the lighting circuit were it is on 100mA time delayed side of consumer unit and change the circuit breaker to a 30mA RCBO.
3. At the point on the lighting circuit were the new cables for the smoke detectors connect to the existing circuit install a 30mA RCD protected fused connection unit.

 

[Deleted member 9648]

The smoke alarms will only require 30ma RCD protection if they include cables buried in the fabric of the building @ <50mm deep...as long as this is not the case they can be protected on the 100ma side......If they are supplied from an existing lighting circuit they must have an independant means of isolation.

 

[bugsy]

One word of caution, if your going to swap your lighting to the RCD side of the CU make sure the landing light dosent use borrowed neutral

 

[millymolly35]

ummm, as clear as mud im starting to think :-( Now I know why you have to be careful to get a fully competant sparky its like a mindfield. The electrician who was going to put the smoke and heat alarms in has suggested using radio frequency ones, therefore not requiring any connecting wires to be run into the walls, they will be run off the lights and each lightling circuit has its own MCB - one for upstairs one for downstairs, he has said that this is fine to leave as it is, but also that he can replace these with RCBO's on these two circuits as they are on the 100MA side. Im concerned that the regs of rented property are more stringent than domestic properties and want to ensure that I get this right the first time, and am not made to make more changes later on. I think the 30Ma RCBO's seem the easist way of ensuring the wiring complies to regulations, that is if ive read what you have all written correctly. Thanks for all of your help its really apprecitated.

 

[baldelectrician]

Where in the UK are you?

 

[millymolly35]

im in kent unfortunatley a long way from scotland

 

[malcolmsanford]

There are a couple of lads from Kent on here, Johnnoboy is in rochester and may be able to give you a little advice. Unfortunately I'm in saudi but the wife is competant and is in Broadstairs................................

 

[millymolly35]

Broadstairs is just around the corner, if she is taking on work can you get her to give me a call on 07779 109733 as im starting to loose the will to live trying to figure out who is actually giving me correct advice. thanks

 

[jon jordan]

One word of caution, if your going to swap your lighting to the RCD side of the CU make sure the landing light dosent use borrowed neutral

hi sorry to hijack this thread but what would you do if the board was a split load on 2 x rcd's and you had borrowed neutral upstairs.?

is there a way around this without rewiring upstairs lighting circuit.
cheers jon

 

[malcolmsanford]

Are you talking about a CU change, as on a PIR there is nothing you could do but code it a 2.

On a CU change then you would have to really just put them on the same RCD as the borrowed neutral would trip if you split the circuits onto 2 different RCD.s On your EIC you would have to mark it down as a departure on the regs under 120.3 and I would also note it on the comments on the existing installation section, that you have advised the client of what you had to do and that the situation should be remidied