I understand that the 17th Ed regs state that connections in live circuits must be accessible for maintenance and inspection, therefore screw type junction boxes can no longer be used in ceiling spaces unless specific access is catered for.
How does this work with low voltage lighting transformers. Many transformers that I have seen have screw type terminals and these are generally placed in the ceiling space in very close proximity to the downlight fitting. Either that or the have small tails for connecting in a connection block. Of course these can be accessed by removing the light fitting - but is that classed as "accessible"? If so, what is stop screw junctions being put anywhere in ceiling spaces as long as they're close to a downlight hole?
Its to make maintenance at a later date a lot easier.
You can use JB's or choc boxes next to a light if its in relation to that lighting circuit & fitting. But would not advise for other circuits that happen to be passing over a light fitting. .
132.12 Accessibility of electrical equipment
Electrical equipment shall be arranged so as to afford as may be necessary:
(i) Sufficient space for the initial installation and later replacement of individual items of electrical equipment
(ii) accessibility for operation, inspection, testing, fault detection, maintenance and repair.
526.3 Every connection shall be accessible for inspection, testing and maintenance, except for the following:
(i) A joint designed to be buried in the ground
(ii) A compound-filled or encapsulated joint
(iii) A connection between a cold tail and the heating element as in ceiling heating, floor heating or a trace heating system
(iv) A joint made by welding, soldering, brazing or appropriate compression tool
(v) A joint forming part of the equipment complying with the appropriate product standard.
529.3 Provision shall be made for safe and adequate access to all parts of a wiring system which may maintenance. NOTE: In some situations. it may be necessary to provide permanent means of access by ladders, walkways, etc.
559 LUMINAIRES AND LIGHTING INSTALLATIONS as can be seen have their own section and when one reads that section it says how lights must be connected. Under the General Common rules it states:-
5184.108.40.206 Connection to the fixed wiring
At each fixed lighting point one of the following shall be used:
(i) A ceiling rose to BS 67
(ii) A luminaire supporting coupler to BS 6972 or BS 7001
(iii) A batten lampholder or a pendant set to BS EN 60598
(iv) A luminaire to BS EN 60598
(v) A suitable socket-outlet to BS 1363-2, BS 546 or BS EN 60309-2
(vi) A plug-in lighting distribution unit to BS 5733
(vii) A Connection unit to BS 1363-4
(viii) Appropriate terminals enclosed in a box complying with the relevant part of BS EN 60670 series or BS 4662
(ix) A device for connecting a luminaire (DCL) outlet according to IEC 61995-1.
Note: In suspended ceilings one plug-in lighting distribution unit may be used for a number of luminaires.
Now when I have connected small spot lights into the suspended ceiling in commercial premises there have been Click plug-in lighting distribution units fixed to the ceiling and all the transformers simply plug in and can be accessed through a panel in the suspended ceiling.
However in DIY home installations there seems to be a lot of corner cutting.
422.3.1 Except for equipment for which an appropriate product standard specifies requirements, a luminaire shall be kept at an adequate distance from Combustible materials. Unless otherwise recommended by the manufacturer, a
small spotlight or projector shall be installed at the following minimum distance from combustible materials:
(i) Rating up to 100 W 0.5 m
(ii) Over 100 and up to 300 W 0.8 m
(iii) Over 300 and up to 500 W 1.0 m
NOTE: A luminaire with a lamp that could eject flammable materials in case of failure should be constructed with a safety protective shield for the lamp in accordance with the manufacturer's instructions.
This means in most cases we need at least 0.5 m between ceiling and floor boards of next floor. My house does not have this gap so to fit flush fittings would mean using a special design recommended by the manufacturer. So in my house only upstairs could I fit flush lights.
Remember we are talking about keeping to regulations. I know regulations are broken but to keep within the regulations it would be very hard in most houses to fit flush lamps. The guides also require wiring to be fixed. Once fixed one can't draw any transformer through a hole for maintenance.
However what is access? When working on the building of a power station holes were left in walls to get equipment into place. Then the wall was bricked up once in place. If it needed to be renewed then the wall would be knocked down to gain access. This wall was not structural so it was considered a valid access. In the same way floor boards could be removed in a house. All that is required is we accept every 10 years carpets will be ripped up and floor boards removed for access. Nothing says we should not do this.
The point I am making the regulations don't say you can't use a junction box using screw connectors under a floor board. It just says you must have access and does not define what access is. Clearly you can't hide wires behind a structural item which could not be removed. However even then where cables can be drawn in and out it would be permitted.
But we hear people say "I can't remove the floor as it has tiles on it" well a lump hammer would soon remove the tiles! What they mean is the cost of removing tiles was not considered when the job was done.
Now we reach the real point "COST" and what we are really talking about is what it will cost to do maintenance if we do it in a certain way. And with cost I don't only mean money but also disruption. To remove a section of plaster board to gain access makes a lot of mess compared with lifting a floor board. And before going ahead with any work as tradesmen we should make the customer aware of likely result if access is required.
I have seen electricians remove sections of plaster board to gain access and as long as the owner has a ceiling which is not rendered in any way and has the original paint to patch up the hole this may be better than removing the laminate floor above the void. However then we are looking at two tradesmen one to do electrics and another to re-instate ceiling.
There is no real answer to your question. It is just a case of costing the alternative methods.
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