light spur from ring main

[Beelzebub666]

I have an outside security light (50W) spurred off the ring main which is on a 32A rcd protected circuit, the thing is it is not on an FCU, just connected straight in. This install was done by registered electricians, my question is have they done it wrong and if so have they done it so wrong that I can demand they come back and fit an FCU for no extra cost?
Thanks

PS if it is wrong, could someone point me to the reg they should have followed?

 

[EFLImpudence]

It really depends if the cable they have used is sufficient to cope with any fault current (which it will be IF RCD protected) or short circuit.
I am assuming you mean a 32A MCB.


Is there not a switch so you can turn it off?

 

[Beelzebub666]

The ring is on a 32A MCB, in a CU with 2 RCD protected groups of MCBs. They've made the connection inside a double outlet straight out through the wall so that the only way to isolate the light is to turn off the mcb in the cu. The light itself operates by detecting light levels and movement, there's no switch. The cable to the light is 2.5mm2 in conduit.

Basically my question is whether the absence of an FCU in this application is just bad practice, or actually a breach of the regs.

 

[ericmark]

559.6.1.6 Lighting circuits incorporating B15. B22. E14. E27 or E40 lampholders shall be protected by an overcurrent protective device of maximum rating 16A.
434.2.1 The regulations in Regulation 434.2 shall not be applied to installations situated in locations
presenting a fire risk or risk of explosion and or where the requirements for special installations and locations specify
different conditions. Amended July 2008

Except where Regulation 434.2.2 or 434.3 applies, a device for protection against fault current may be installed
other than as specified in Regulation 434.2. under the following conditions:

The part of the conductor between the point of reduction of cross-sectional area or other change and the position of
the protective device shall:
(i) not exceed 3 m in length, and
(ii) be installed in such a manner as to reduce the risk of fault to a minimum, and
NOTE: This condition may be obtained. for example, by reinforcing the protection of the wiring against external influences
(iii) be installed in such a manner as to reduce to a minimum the risk of fire or danger to persons.
433.2.1 Except where Regulation 433.2.2 or 433.3 applies, a device for protection against overload shall be
installed at the point where a reduction occurs in the value of the current-carrying capacity of the conductors of the
installation.
559.4.1 Every luminaire shall comply with the relevant standard for manufacture and test of that luminaire and shall be selected and erected in accordance with the manufacturer's instructions.

It is hard to say exactly what regulation if any has been breached, the regulations don't say things like "A FCU must be used" they are more vague as there may be some situation where some massive flood lamp does need a 32A supply. But I am sure the instructions for your lamp will state at some point the maximum rating of the protective device? My copy of BS7671 is out of date, I am told there is a change to following manufacturers instructions in amendment 3.

Unless the electrical firm is willing to do the correction as a good will thing, then either the scheme provider or LABC would need to get involved. For the cost involved it is unlikely to be worth doing that? Specially as it's so hard to show it's wrong. We have argued on this forum many times over the 3 meter rule before the protective device, with an unfused spur I feel this applies and no unfused spur should be over 3 meters long, however others disagree and say as long as it is within the volt drop and loop impedance limits then you can have it as long as you like. The same goes for ovens supplied from a cooker supply of 32A, ovens are generally designed for a 16A supply, however there is often nothing in the instructions which says they can't be used on a 32A supply, and cooker connection units are made specially to allow both the hob and oven to be supplied from the same cable into the kitchen. In fact in some cases there is a 45A supply which is well over the value which the internal wires of an oven will take if there is a fault.

It is down to the electricians warranty of skill, and he has to decide what is safe and reasonable. It is hard to show his actions are wrong until something goes wrong.

I personally think it is wrong to supply an item from a ring which can draw over the current carrying capacity of the cable under fault conditions without opening a protective device. However you are permitted a double socket on a unfused spur so you could draw 26A but with most installation methods the cable is not rated at 26A, however we all know even if in theory you can overload the cable, in practice it is very unlikely. So I think it is unlikely you can force the electrical firm to correct FOC, but they may correct FOC as a good will gesture.

I will guess there is a rating on the PIR which has been well exceeded and also should you get water ingress then the RCD will trip and you have no way to isolated so I would say the following has not been complied with.

314 DIVISION OF INSTALLATION
314.1 Every installation shall be divided into circuits, as necessary, to:
(i) avoid hazards and minimize inconvenience in the event of a fault
(ii) facilitate safe inspection, testing and maintenance (see also Section 537)
(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
(iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced
by equipment in normal operation
(v) mitigate the effects of electromagnetic interferences (EMI)
(vi) prevent the indirect energizing of a circuit intended to be isolated.
314.2 Separate circuits shall be provided for parts of the installation which need to be separately controlled, in such a way that those circuits are not affected by the failure of other circuits, and due account shall be taken of the consequences of the operation of any single protective device.
314.3 The number of final circuits required. and the number of points supplied by any final circuit, shall be such as to facilitate compliance with the requirements of Chapter 43 for overcurrent protection, Section 537 for isolation and switching and Chapter 52 as regards current-carrying capacities of conductors.
314.4 Where an installation comprises more than one final circuit, each final circuit shall be connected to a separate way in a distribution board. The wiring of each final circuit shall be electrically separate from that of every other final circuit, so as to prevent the indirect energizing of a final circuit intended to be isolated.

 

[Beelzebub666]

Thanks for the replies

 

[deadshort]

Hi, are you 100% certain it's protected by a 32a mcb ? If it is, then get them back to rectify and add a FCU.

HNY,

DS

 

[JohnW2]

As has been said, it is not difficult to think of regulations which one could argue had been (or may have been) violated. However, as implied by some of the above responses, I would (regulations aside) personally not be too concerned about the lack of 'fusing down' in an FCU, but would be more concerned about the lack of any means of switching/isolating the light. As has been said, if it fills with water (not unknown), it will cause the RCD to trip, and hence will result in all circuits disabled by the same RCD being unusuable until the light were repaired, replaced or disconnected. An FCU would afford such a means of isolation.

Having said all that ('pragmatically') I certainly would have expected any competent electrician to have installed an FCU.

Kind Regards, John

 

[Beelzebub666]

So I gather the consensus is it was bad practice but not so obviously wrong that I can call them back without a bunch of argument and complaining to the governing body, which is probably just not worth it for a single FCU. Would it be fair to say you all agree that it is worth fitting an FCU regardless of who has to pay for it? Would that prevent a fault in the outside light taking out half the circuits in the house?

 

[EFLImpudence]

So I gather the consensus is it was bad practice but not so obviously wrong that I can call them back without a bunch of argument and complaining to the governing body, which is probably just not worth it for a single FCU.

Probably.

Would it be fair to say you all agree that it is worth fitting an FCU regardless of who has to pay for it?

You could do with A double pole switch so it may as well be an FCU.

Would that prevent a fault in the outside light taking out half the circuits in the house?

Well, it won't prevent it happening but when it does, you can turn it off and then turn on the rest of the lights.

 

[deadshort]

Fit a FCU with a 3a fuse fitted, that's what an electrician would do. As you say, in the event of a fault you can isolate the external wiring.

Regards,

DS

 

[JohnW2]

Would it be fair to say you all agree that it is worth fitting an FCU regardless of who has to pay for it?

That would certainly be the normal (and desirable) way.

Would that prevent a fault in the outside light taking out half the circuits in the house?

It would not prevent that happening (assuming that an RCD was being tripped by a fault) but, provided it was a switched FCU, it would enable you to isolate the power to the outside light so that you could then restore power to everything else. Without a switch, you would 'lose half the circuits in the house' until the problem with the outside light was sorted.

Kind Regards, John