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[Figureman52]

Hope someone can help.

I have a couple of floodlights wired  together and operated through an ordinary light switch off the lighting circuit, which is not RCD protected. If I connected another feed to them via a separate pir detector coming off the ring main, which is RCD protected, would it work, or is it likely to keep tripping out?

Thanks.

[dave the builder]

That is a BIG NO NO ! 
and if you have to ask ,you should seek out professional help.
and your current light switch controlling the lights should be a double pole switch anyway ,preferably a switched fused spur
 

[Lizzie Zoom]

That is a BIG NO NO ! 
and if you have to ask ,you should seek out professional help.
and your current light switch controlling the lights should be a double pole switch anyway ,preferably a switched fused spur

Indeed!!

Last year I had to urgently disconnect a security light on the side of my daughters house that was running off the ceiling rose in her bedroom without any isolation switches, fused spurs, and running on 2.5 cable, which really reflected the lack of knowledge of legal electrical installations and regulations by whatever idiot installed it all!

As Dave says, if you lack the knowledge to carryout such work, then do not do it and only allow suitably qualified electricians to do so.  That could avoid you being prosecuted if things go very wrong.

[dave the builder]

Yes , there are some bad DIYers out there that give us proper cowboy builders a bad name 
Electricity is very expensive and you don't want it leaking out all over people 

[Figureman52]

Thanks for the advice. It felt wrong to me anyway, which is why I asked.

[Marks DTM Calib]

That is a BIG NO NO ! 
and if you have to ask ,you should seek out professional help.
and your current light switch controlling the lights should be a double pole switch anyway ,preferably a switched fused spur

Not if its off a lighting circuit it doesn't, single pole is absolutely fine.

The real issue is the wattage of the outside lights, if they are stonking halogen jobs then they will exceed the rating of the lighting circuit.

Agreed you need a fused spur (plus appropriate rated fuse) with isolator if they are fed from a ring main to provide the correct upstream protection. 

[Marks DTM Calib]

That is a BIG NO NO ! 
and if you have to ask ,you should seek out professional help.
and your current light switch controlling the lights should be a double pole switch anyway ,preferably a switched fused spur

Indeed!!

Last year I had to urgently disconnect a security light on the side of my daughters house that was running off the ceiling rose in her bedroom without any isolation switches, fused spurs, and running on 2.5 cable, which really reflected the lack of knowledge of legal electrical installations and regulations by whatever idiot installed it all!

As Dave says, if you lack the knowledge to carryout such work, then do not do it and only allow suitably qualified electricians to do so.  That could avoid you being prosecuted if things go very wrong.

Virtually nothing wrong at all with that Lizzie, 2.5mm is fine assuming it fits the terminals ok, feeding an outside light of the lighting circuit is also OK as long as the circuit is not overloaded, isolation in this application only has to be available to the live connection.

[STEMO]

I have two outside security lights fed from a single pole switch in the kitchen, on the lighting circuit. The are 10W leds.

[Viral_Jim]

I have two outside security lights fed from a single pole switch in the kitchen, on the lighting circuit. The are 10W leds.

From the sounds of it, it's a miracle you haven't burned down half the street. Lizzie will be along imminently to chastise you vigorously!

[dave the builder]

That is a BIG NO NO ! 
and if you have to ask ,you should seek out professional help.
and your current light switch controlling the lights should be a double pole switch anyway ,preferably a switched fused spur

Not if its off a lighting circuit it doesn't, single pole is absolutely fine.

The real issue is the wattage of the outside lights, if they are stonking halogen jobs then they will exceed the rating of the lighting circuit.

Agreed you need a fused spur (plus appropriate rated fuse) with isolator if they are fed from a ring main to provide the correct upstream protection. 

It's an outside light ,so special location, requires double pole isolation from the lighting circuit which someone decided to connect it to,
fused spur is a double pole switch
if the outside light is powered by a plug (with correct sized fuse),which can be removed from a socket *with RCD protection (thus giving double pole isolation) it is effectively a portable appliance, not notifiable.
in this case, the lighting circuit is RCD protected ,(from what the OP said)
However, not all installations are up to date ,dual RCD consumer units or better.
some are ye olde wylex re-wirable  antiques with no RCD or even decent overcurrent protection 

I have two outside security lights fed from a single pole switch in the kitchen, on the lighting circuit. The are 10W leds.

so when water gets into your cheap Chinese LED security lights , how do you isolate them ? assuming your still alive ?
are your lighting circuits RCD protected ?
you'll need a torch to see to reset the RCD because  it will have taken out your lights too (if night time ,but such problems rarely happen in daylight or at convenient times)

[Migv6 le Frog Fan]

My outside security light is wired to a 13 amp plug and plugged into a socket in the bedroom. 

[dave the builder]

My outside security light is wired to a 13 amp plug and plugged into a socket in the bedroom. 

wow , do you have a massive back garden that requires 3 kw of lighting 
or have you put the correct rated fuse in the plug 
also, have you checked your upstairs sockets are rcd protected ?
some older installations had downstairs RCD protected sockets only (in case you plug a mower in and decide to mow the lead) some don't even have RCD at all .

STAY SAFE people , this newfangled electrickary is nasty stuff
(check your electric bill if you don't believe me £££  )

 

[Lizzie Zoom]

That is a BIG NO NO ! 
and if you have to ask ,you should seek out professional help.
and your current light switch controlling the lights should be a double pole switch anyway ,preferably a switched fused spur

Indeed!!

Last year I had to urgently disconnect a security light on the side of my daughters house that was running off the ceiling rose in her bedroom without any isolation switches, fused spurs, and running on 2.5 cable, which really reflected the lack of knowledge of legal electrical installations and regulations by whatever idiot installed it all!

As Dave says, if you lack the knowledge to carryout such work, then do not do it and only allow suitably qualified electricians to do so.  That could avoid you being prosecuted if things go very wrong.

Virtually nothing wrong at all with that Lizzie, 2.5mm is fine assuming it fits the terminals ok, feeding an outside light of the lighting circuit is also OK as long as the circuit is not overloaded, isolation in this application only has to be available to the live connection.

I was making the point that whoever used 2.5 cable to a lighting circuit was showing a lack of knowledge, as no electrician would use that rated cable in such a manner.

As for a switch to the live, there was nothing in any form of switch and isolating fused spur. Therefore if the external light had become faulty it would trip the lighting circuit breaker and, without climbing up ladders to find the fault, would have resulted in the lighting being off for some time as anyone investigating the fault would not have known for a bit that the outside light was causing the problem.  There was no visible sign of any connection internally, and no way to isolate the external circuit.  To me that is at least bad and unsafe practice.

[STEMO]

Yes, mine are RCD protected. They were neither cheap nor Chinese, I fitted them, not a cowboy builder. 
The lights are sealed units, with a tail, which is wired into a weatherproof junction box.

[Varche]

How many forum members does it take to answer an electrical question?

23 including one real cowboy builder to give the correct answer, ten other also correct answers, one to call the fire brigade and one smart ass to make a funny comment .


PS STEMO. 10 w LED security lights? They are underpowered. Even pointing in the right direction they will be unable to illuminate your neighbours bedroom fully as they switch on and off each time a fox, cat or Amazon delivery van goes by. Two of these for example but they would need their own fused spur!   https://www.ebay.co.uk/itm/300W-LED-FLOOD-LIGHTS-INDUSTRIAL-HIGH-BAY-STADIUM-SECURITY-FLOODLIGHTS-UK/291414522263?hash=item43d9a8b997:m:mAsdOYnC3QPp3ttlhaUTTBg:rk:3:pf:0

[dave the builder]

Virtually nothing wrong at all with that Lizzie, 2.5mm is fine assuming it fits the terminals ok, feeding an outside light of the lighting circuit is also OK as long as the circuit is not overloaded, isolation in this application only has to be available to the live connection.

what about nuisance tripping of the RCD  , circuit identification , local isolation for maintenance etc 
just because building regulation part p dropped mention of outside lights , does not give carte Blanche to ignore bs7671  . or revert to  15th edition practice               

I was making the point that whoever used 2.5 cable to a lighting circuit was showing a lack of knowledge, as no electrician would use that rated cable in such a manner.

As for a switch to the live, there was nothing in any form of switch and isolating fused spur. Therefore if the external light had become faulty it would trip the lighting circuit breaker and, without climbing up ladders to find the fault, would have resulted in the lighting being off for some time as anyone investigating the fault would not have known for a bit that the outside light was causing the problem.  There was no visible sign of any connection internally, and no way to isolate the external circuit.  To me that is at least bad and unsafe practice.

indeed , shoddy work
call the installer back and attach his/her genitals direct to the main incomer 
2.5 is an issue(not because of the size of conductor) BUT if it is flat twin and earth , it is not uv stable, so not ok to run unprotected outside to a light 

How many forum members does it take to answer an electrical question?

23 including one real cowboy builder to give the correct answer, ten other also correct answers, one to call the fire brigade and one smart ass to make a funny comment .

if building control and IET can't agree , what chance has joe public

PS STEMO. 10 w LED security lights? They are underpowered. Even pointing in the right direction they will be unable to illuminate your neighbours bedroom fully as they switch on and off each time a fox, cat or Amazon delivery van goes by. Two of these for example but they would need their own fused spur!   https://www.ebay.co.uk/itm/300W-LED-FLOOD-LIGHTS-INDUSTRIAL-HIGH-BAY-STADIUM-SECURITY-FLOODLIGHTS-UK/291414522263?hash=item43d9a8b997:m:mAsdOYnC3QPp3ttlhaUTTBg:rk:3:pf:0

or other appropriate means of double pole isolation and overcurrent & RCD protection 
these LED rarely pull anything like the stated rated current 
but will pull more ,IF a person is in contact with live parts 

[STEMO]

10W is enough to see us out and in. In fact, I had to point one downwards as a neighbour said they were too bright. So up yours, Roy Rogers 

[dave the builder]

10W is enough to see us out and in. In fact, I had to point one downwards as a neighbour said they were too bright.with the electrical fires burning the house down as well and the blue lights on the fire engines ,So up yours, Roy Rogers 

FTFY Mr STEMO 

[Marks DTM Calib]

It's an outside light ,so special location, requires double pole isolation from the lighting circuit which someone decided to connect it to,
fused spur is a double pole switch
if the outside light is powered by a plug (with correct sized fuse),which can be removed from a socket *with RCD protection (thus giving double pole isolation) it is effectively a portable appliance, not notifiable.
in this case, the lighting circuit is RCD protected ,(from what the OP said)
However, not all installations are up to date ,dual RCD consumer units or better.
some are ye olde wylex re-wirable  antiques with no RCD or even decent overcurrent protection 

I think you have fallen foul of the common sparky myth! (the regs can be complex in their wording in places)

Its not required as the regs are vague, yet practical. They state that all live conductors must have a means of isolation and reading deeper, this does not have to be specific to that circuit. Hence the main double pole isolator in the board satisfies that requirement.

In fact you don't need a switch at all based on the regs as isolation can be supported via the MCB or removable fuse and double isolation supported again by the main incomer.

[Doctor Gollum]

I have two outside security lights fed from a single pole switch in the kitchen, on the lighting circuit. The are 10W leds.

From the sounds of it, it's a miracle you haven't burned down half the street. Lizzie will be along imminently to chastise you vigorously!

You should probably film that

[ronnyd]

Idiot across the road located his security light right near the flue of his combi boiler. Every time the vapour is blown in the wind the light goes on and shines in our lounge . Also he has three cats that walk along the top of his wall and they keep triggering it as well. Think i will have to take out the PIR with my airgun.