Advice on extension wiring

no8080 · Mar 21, 2011

Hi,

I am after some advice,

I am having an extension build to my dining room, I have a modern house, 2007 and I want to install the electrics myself. I am a skilled enough person have good knowledge of electric wiring, safety etc.

I questions are basically to check if there is anything new or different I have to do in order to comply with any new regs, etc. I fairly confident the work does not need to be covered under part p, but as part of the building consent for the extension the details of this work have been roughly covered in the original plans sent to building control.

My plans are to extend the current lighting and ring main circuits, basically I want to add a new light fitting to the existing dining room lighting circuit, so it runs off the same switched circuit, I will use 1 run of cable to supply the neutral and switched live from the existing light fitting to the new one.

Then a set of LV downlights (12v 20watts max per bulb) in the ceiling, running off a transformer controlled via a normal light switch, so a new wiring leg taken off the existing lighting circuit and a new cable to the light switch for the switch control.

1.5mm twin & earth cable for the lighting.

The existing sockets are a ring main, using 2.5mm cable, so I plan to break the ring in the ceiling and add a juction box and then run 4 double sockets and then rejoin back to the ring main via another junction box.

2.5mm twin & earth for the sockets.

Any cable that runs down the walls behind plasterboard or insulation will be covered in plastic capping or trunking.

Does this sound OK,

Thanks in advance

Neil

IQ Electrical · Mar 21, 2011

no8080 said:
Hi,

I am after some advice,

I am having an extension build to my dining room, I have a modern house, 2007 and I want to install the electrics myself. I am a skilled enough person have good knowledge of electric wiring, safety etc.

I questions are basically to check if there is anything new or different I have to do in order to comply with any new regs, etc. I fairly confident the work does not need to be covered under part p, but as part of the building consent for the extension the details of this work have been roughly covered in the original plans sent to building control.

My plans are to extend the current lighting and ring main circuits, basically I want to add a new light fitting to the existing dining room lighting circuit, so it runs off the same switched circuit, I will use 1 run of cable to supply the neutral and switched live from the existing light fitting to the new one.

Then a set of LV downlights (12v 20watts max per bulb) in the ceiling, running off a transformer controlled via a normal light switch, so a new wiring leg taken off the existing lighting circuit and a new cable to the light switch for the switch control.

1.5mm twin & earth cable for the lighting.

The existing sockets are a ring main, using 2.5mm cable, so I plan to break the ring in the ceiling and add a juction box and then run 4 double sockets and then rejoin back to the ring main via another junction box.

2.5mm twin & earth for the sockets.

Any cable that runs down the walls behind plasterboard or insulation will be covered in plastic capping or trunking.

Does this sound OK,

Thanks in advance

Neil

I don't have access to Document P right now but I'm sure extra low voltage lighting is notifiable unless using pre-assembled fittings as a pre-assembled kit.

Cables buried in walls at depths of less than 50mm must have RCD protection or earthed mechanical protection.

no8080 · Mar 21, 2011

IQ Electrical said:
I don't have access to Document P right now but I'm sure extra low voltage lighting is notifiable unless using pre-assembled fittings as a pre-assembled kit.

Cables buried in walls at depths of less than 50mm must have RCD protection or earthed mechanical protection.

The ring main of the sockets is already on an RCD protected circuit, so this is ok, but the lighting circuits are not I don't believe. My CU is a split load with a mains switch and 1x 30ma RCD. The lighting circuits are on the normal non-RCD side.

The 12V lighting will be a kit type bought as a single unit, lights and transformer together, although if this is an issue with part P, I can swap them for a set of mains halogen downlights.

The lighting circuit, as this is not on a RCD, do I need the CU upgrading to an RCD for the lighting? If so I assume an RCBO for the lights would accomplish this to requirements?

Thanks

Neil

IQ Electrical · Mar 21, 2011

no8080 said:
The ring main of the sockets is already on an RCD protected circuit, so this is ok, but the lighting circuits are not I don't believe. My CU is a split load with a mains switch and 1x 30ma RCD. The lighting circuits are on the normal non-RCD side.

The 12V lighting will be a kit type bought as a single unit, lights and transformer together, although if this is an issue with part P, I can swap them for a set of mains halogen downlights.

The lighting circuit, as this is not on a RCD, do I need the CU upgrading to an RCD for the lighting? If so I assume an RCBO for the lights would accomplish this to requirements?

Thanks

Neil

It will.

Check the ELV lighting requirements, I'm going from memory!

malcolmsanford · Mar 21, 2011

special installation" means an electric floor or ceiling heating system, an outdoor lighting or
electric power installation, an electricity generator, or an extra-low voltage lighting system
which is not a pre-assembled lighting set bearing the CE marking referred to in regulation 9 of
the Electrical Equipment (Safety) Regulations 1994(a);
Taken from the Part P doc

IQ was spot on about this and if they are as you say they are pre assembled in a kit you don't need to class them as a special installation.

My major concern is though the work is not notifiable it will still need to have a MEIWC issued on the extending of the circuits, which will mean testing the circuits and obtaining the results with a calibrated meter, do you pocess either either the knowledge or the meter

You will also need to insure that the Junction Box for extending the ring final is accessible for future testing or maintenance.

IQ Electrical · Mar 21, 2011

malcolmsanford said:
special installation" means an electric floor or ceiling heating system, an outdoor lighting or
electric power installation, an electricity generator, or an extra-low voltage lighting system
which is not a pre-assembled lighting set bearing the CE marking referred to in regulation 9 of
the Electrical Equipment (Safety) Regulations 1994(a);
Taken from the Part P doc

IQ was spot on about this and if they are as you say they are pre assembled in a kit you don't need to class them as a special installation.

My major concern is though the work is not notifiable it will still need to have a MEIWC issued on the extending of the circuits, which will mean testing the circuits and obtaining the results with a calibrated meter, do you pocess either either the knowledge or the meter

You will also need to insure that the Junction Box for extending the ring final is accessible for future testing or maintenance.

It almost stretches the reason for a Minor Electrical Installation Works Certificate even though the 'new circuit' criteria is satisfied!

I'd put the whole lot on an Electrical Installation Certificate and probably just notify it too.

Dunc · Mar 21, 2011

malcolmsanford said:
You will also need to insure that the Junction Box for extending the ring final is accessible for future testing or maintenance.

Through crimps in a 'choc box' to enclose the connections and provide strain relief would negate the need for accessing the connections. Tend to do this a lot these days when extending ring mains or replacing damaged sections of cabling. Price is comparable material wise and the time taken to make them off isn't too dissimilar either.