RCD for lighting alterations

[Hefferl]

I need to alter an existing lighting circuit which is currently on a BS 3871 MCB (Old Style) These alterations will mean an RCD is necessary. I was considering using an RCD spur (fused down to 5A) fitted next to consumer unit (which has no RCD protection). Is this acceptable and is it the easiest / most cost effective solution here?

 

[matt.leung]

a lighting circuit does not always have to be on an RCD circuit as all u ru doing is making alterations.

 

[Hefferl]

these alterations will involve cables being concealed in wall <50 mm from surface.

 

[monkey5]

i would place rcd fcu next to fuse board and feed it from the existing fuse then feed all the lights from rcd unit,if that makes sense.

wayne

 

[PC Electrics]

Your plan is sound. But don't forget too that you need to check earthing and bonding are adequate.

 

[SPECIAL LOCATION]

I need to alter an existing lighting circuit which is currently on a BS 3871 MCB (Old Style) These alterations will mean an RCD is necessary. I was considering using an RCD spur (fused down to 5A) fitted next to consumer unit (which has no RCD protection). Is this acceptable and is it the easiest / most cost effective solution here?

All good...

My only comment would be...

I would probably leave the RCD spur with a 13A fuse in. :|

Reasons:-

• The overload protection is still provided by the 3871 MCB.
  
• The RCD protection element is provided by the spur.
  

SO

In the event of an "Earth leakage" fault the RCD spur will trip..

BUT

In the event of an "Overload" fault its a bit of pot luck..

maybe the '3871 MCB' or maybe the '1362 in the RCD' Spur...

Or maybe BOTH!

I would be considering minimising inconvenience and confusion for the customer

so leave the Spur as 13A then its just gonna be the 3871 that trips on overload.

:coffee