Radial circuit

[grahammm]

Hi,

So there's an armoured cable running from a B32 MCB to a twin socket in the garage. That's the exisiting setup.

MCB ----> twin socket

I'm looking at doing this, is this safe? I'm running it in 2.5mm2 twin+earth.

MCB ----> twin socket ------> 13A FCU (for a fluorescent tube) ------> wired in switch for a floodlight -----> wired in switch for a floodlight.

Thanks,

Graham

 

[Iggifer]

not fully sure I understand your plan, but you will only need 2.5 from the socket to the fcu (and put a 3/5a fuse in it) then use 1mm or 1.5mm for your lighting circuit. Will be much easier to work with, particularly in lighting terminals.

What size is the armoured cable? 4mm? 2.5mm? If it's 2.5 I'd be concerned it's protected by a 32A breaker

 

[grahammm]

Hi Iggifer! Thanks for the reply and help.

I've recently moved in to somewhere and the armoured cable and twin socket was installed in the garage. I now want to expand to add a fluorescent tube for in the garage and a floodlight on front and back!

In terms of the size of the armoured cable, it's pretty chunky but I don't know as it was installed before me. I'll check!

 

[Iggifer]

it may well be printed on the black sheath

 

[riveralt]

You will also want the cable length - just to check the voltage drop.
I would get floodlights with PIR's built in.
Then I would run cable from the socket to the switched FCU then load side 1mm T&E to a single gang switch then onto your garage light.
Also from the FCU load side another 1mm T&E to the flood lights loop into one and out to the other.
Use a switched FCU because some PIR floodlights have the ability to double flick the switch to over ride the PIR.

 

[JohnW2]

Then I would run cable from the socket to the switched FCU then load side 1mm T&E to a single gang switch then onto your garage light. ... Also from the FCU load side another 1mm T&E to the flood lights loop into one and out to the other. ... Use a switched FCU because some PIR floodlights have the ability to double flick the switch to over ride the PIR.

That would certainly work, but I would personally put a double-pole switch in the feed to the two PIR floodlights, in case they get 'flooded' (by rain!) and need to be isolated to prevent an RCD tripping. With what you propose, that could be done with the switched FCU, but the OP would then loose his light in the garage until the floodlight problem was sorted out. The FCU could then be unswitched if one wanted.

Kind Regards, John

 

[ericmark]

I would tend to use switched FCU's as light switches then you have double pole switching and fuse which you can remove if a light becomes faulty.

All new wiring should be RCD protected likely easy way if not already protected is a RCD FCU.

 

[EFLImpudence]

All new wiring should be RCD protected likely easy way if not already protected is a RCD FCU.

Not mandatory if visible in a garage.

The socket should be though.

 

[ericmark]

All new wiring should be RCD protected likely easy way if not already protected is a RCD FCU.

Not mandatory if visible in a garage.

The socket should be though.

The BS7671:2008 is not law so yes not mandatory but I was lead to understand with the amendment 3 the rules had changed? I have not bought amendment 3 I expect my son will ask me to get a copy soon as being a member of the IET it's cheaper for me to buy.

The question is when is a socket not a socket? If I have a BA22d socket am I to take this does not count as a socket?

 

[EFLImpudence]

The BS7671:2008 is not law so yes not mandatory but I was lead to understand with the amendment 3 the rules had changed?

I did not mean mandatory in that way, just that RCD protection is not required for visible cables (unless required for other reasons).

The question is when is a socket not a socket?

When it's not a socket?

If I have a BA22d socket am I to take this does not count as a socket?

The RCD requirements for sockets relate to hand held tools so...

Probably best not to use BA22d for that purpose thus removing the problem.

 

[ericmark]

My gran always used a lighting socket for the smoothing iron. There were only 2 15A sockets in the house so it was normal to use a BA22d splitter with a switch on one outlet and a BA22d to 5 amp two pin adaptor and plug the iron into that which also resulted in the cable not getting in the way while ironing.

Yes I know today this is frowned on and the splitters and adaptors are no longer sold in Woolworths but they are still sockets. I have an old BA22d plug in my test kit to test the ELI I am sure many others also have them.

Even today we have

so sockets are still fitted on lighting circuits.

 

[EFLImpudence]

Yes, I, too, remember using those for the iron.


Anyway, I'm not sure what you are asking but:

411.3.3 - In a.c. systems additional protection by means of an RCD shall be provided for:
(i) socket-outlets with a rated current not exceeding 20A

Part 2 - Socket-outlet. A device, provided with female contacts, which is intended to be installed with the fixed wiring, and intended to receive a plug. A luminaire track system is not regarded as a socket-outlet system.

Does a BA22d have female contacts and does it receive a plug?

If you consider the BA22d a socket-outlet then all such lighting circuits should be RCD protected...

...but not because of a visible cable.

 

[ericmark]

Since it states "A luminaire track system is not regarded as a socket-outlet system." then clearly the regulations do not intend to include lighting plugs and sockets.

But clearly they still are plugs and sockets and as such should some one do something silly and get injured it would be for the courts to decide.

Personally I have only had one good belt in the 30 years I have lived in this house and that was from the lighting circuit which was RCD protected but 40 mS is a long time to get an electric shock for and did result in my falling to the ground.

As to if it had not been RCD protected would it have been any different I don't know and not inclined to test it. Likely it would not have made any difference I am sure falling to the ground would have disconnected me.

My fault I will admit I should have used a cable tester first horizontal cables are permitted although I had not expected to find them where I was working.

However I still feel 100% RCD protection in my house was the right move.

 

[ban-all-sheds]

So there's an armoured cable running from a B32 MCB to a twin socket in the garage. That's the exisiting setup.

MCB ----> twin socket

Yes, we know.

Why have you started a new topic?

 

[JohnW2]

Personally I have only had one good belt in the 30 years I have lived in this house and that was from the lighting circuit which was RCD protected but 40 mS is a long time to get an electric shock for and did result in my falling to the ground.

Are you saying that the RCD operated?

As I recently commented, the problem as regards normal use by householders etc. (not those 'working on a circuit') is that most lamp holders are plastic and most light fittings are Class II, hence with no exposed earthed parts. Any significant shock they receive (e.g. if the poke their finger into a lamp holder) is therefore likely to be an L-N one, hence not something that RCD protection can do anything about.

Kind Regards, John