18th question.

My opinion here will deviate from what is stated in BS 7671, and, for some crazy reason that there has been no explanation of the product standard for RCD socket outlets (and fused connection units) have been removed from BS 7671:2018, so that could require a deviation, me, I'd not worry and fit one, including a deviation if necessary.

The requirement in BS 7671:2018 is that ALL socket outlets in domestic premises must be RCD protected.

All new wiring should be rcd protected now including lighting cables not buried less than 50mm or in trunking.


Gary

Presuming that the C.C.T.V. system is supplying its cameras at extra low Voltage and is probably earth free as well, there is little shock risk in supplying the new socket from the existing lighting circuit. The C.C.T.V. system may also be a Class II system which needs no earthing. Would we need a R.C.D. protected socket for a t.v. loft aerial amplifier supplied with a two core flex for safety reasons?


Table 52.3 requires a minimum cable size of 1.5mm2 for "power" circuits as opposed to a "lighting" circuit.


Although people often miss NOTE.4:"For Lighting circuits AND associated small items of current using equipment, such as a bathroom extractor fan". 1.0mm2 can be used.


You could wire in the C.C.T.V. recording unit via a switched fused connection unit fused at 3 Amp. from the lighting circuit. I would.


Do the manufacturers require the C.C.T.V. equipment to be protected by an R.C.D?


It is quite possible that we could apply the exception in 411.3.3 where the requirement for an R.C.D. can be done away with for FELV and reduced Voltage systems. NOTE. 3: "A lighting distribution unit complying with B.S. 5733, luminaire track system, LSC or DCL is not regarded as a socket outlet for the purpose of this regulation."


Sometimes common sense is required in applying the regs.


Will the loft get too hot for the recording unit or power supply in the summer and damage it?


Z.

I suggest to the letter of the regs it is not compliant in a domestic setting, but in terms of being dangerous or illegal certainly not so no issues,

It is not really going to be used for portable equipment, and the class I / class II thing is a 'red herring', So long as the lights have a CPC, so the Zs can blow either the fuse in the plug, or more likely, knock off all  the lights, there is ADS, and  it poses no more risk than any building wired a few years ago, of which there are a great many in daily use that are far more risky than this.  Actually in older buildings a shock from a crumbling plastic lamp holder when bulb changing or or damage to a light switch by enthusiastic kids with a cricket bat or adults making a careless furniture removal are similarly small but greater risks that may be improved by RCD. These are acceptable risks that do not require addressing until the lighting wiring  or the CU are all being re-done, so  I'd not be kept awake by it, I'd suggest neither should you. 

Biggest risk may be an EICR fail at some future point, and the fix for that is an RCD socket or an RCBO at the CU.

For completeness, the MWC needs to be clear that the socket is not for anything more than just the CCTV, and the rest of the existing cct is to the 16th edn,

Table 52.3 is nonsensical.

I have decided to go back and change the socket for an rcd one, I don't know why I didn't think of that in the first place

Probably because the the standard for RCD sockets (BS 7288) isn't listed as being acceptable for providing additional protection under the 18th (531.3.6) - must be BS EN 61008, 61008 or 62423.


  - Andy.

I used an RCD protected socket on one of my jobs that got inspected the inspector had no issues with it, installed to the 18th. Protected by a standard mcb, cable was singles in galv 20mm conduit. So I guess it depends on the installation method too. 


Ts

Hi, I would say using a 13A socket fed from the upstairs lighting circuit could be a deviation from the regulations as the socket could be used for something else and since you have not said what size the cable is for the lighting circuit, it was common practice at one time to use 1.0mm twin and cps cable for the lighting circuit, I would have run a dedicated 2.5mm radial circuit and since the latest edition of the regulations specify RCD protection where the cables are not enclosed in a metallic enclosure when buried in the walls in a new installation this would pose a problem unless of course you used MICC cable to feed the socket. As the installer/designer you will take ultimate responsibility for the installation. I would say that installing a 13A socket into a lighting circuit would be a deviation from the regulations as you have no control on what the consumer could do with that socket, yes the circuit protective device would ultimately protect the circuit. I believe that you would also have to carry out a Risk Assessment for that circuit to justify it, see Regulation 411.3.3 also you would have to check Maximum Disconnection time see table 41.1.

Nowhere do the regs say you can't have a socket on a lighting circuit, nor does it say that you must supply a 13A socket from a supply capable of supplying 13A or more.  It is of course jolly awkward if you do plug in a 2kw fan heater and the lights go out, but no regulations have been breached, nor is there a risk of cables being overload or a fire, as long as the MCB for the lighting circuit matches the current rating of the cables used.


The only aspect is that the new works need RCD protection if there are new cables are concealed  in a wall  or similar to less than 50mm (but clearly visible surface wiring is OK) and the new socket needs RCD protection.