Question for the electricians

[Ozi]

How do you trim cable for LED lamps?

I was always taught to keep the outer insulation in the cable clamp or inside the junction box, so like the first picture, I'm being told this is wrong as the clamp does not fully close, it holds just as securely and looks better than the second photo to me but what would a professional say?

Ignore the monstrosity in the back ground that's what's being replaced.

 

[Phill05]

I would say 1st image is correct as gripping the sheath helps stop the wires being ripped out and looks tidy.

 

[TheUnicorn]

not an electrician, but I am a qualified PAT tester, and if that were a plug with the wires (internal insulation) exposed it would fail, on that logic I would agree with your first instinct that the outer layer should be clamped. who has told you otherwise?

 

[joncooper27]

What make/model is the downlight?
Does it come with any termination instructions?
Take a pic with the cover open

 

[Sideways]

I assume here that the lamp includes the low voltage transformer and the cable is carrying mains voltage ?
In the case of photo #2 the cable clamp is biting down and damaging the only layer of insulation separating a person from the live conductor. I don't have a copy of the blue book to quote section numbers at you but I think that's thoroughly non compliant as you expected.

What standards compliance markings are on the unit ?
What size is the cable (cross sectional area) ?

 

[joncooper27]

What make/model is the downlight?
Does it come with any termination instructions?
Take a pic with the cover open

I normally use JCC V50 LED down lights selectable between warm and cool white. A nice junction box to terminate into that plugs into the down light. They also have a detachable bezel so you can put them on once painted.

 

[HappyHacker]

The sheath should be contained in the enclosure. I don't have the regulation to hand but from memory is one of the tick box items on an Electrical Inspection and Condition report.

Unfortunately many fittings do not appear to cope with UK T&E and or flex sizes. I regularly curse and swear when trying to wire up fittings which seem to be designed to take nothing bigger than 0.5sq mm cable.

I did query a mains down lighter which had what appeared to be accesible unsheathed insulated singles connecting the light to the connector block. The supplier said it was insulated and sheathed. I cut the cable and managed to the determine the sheath was present and measured it to be less than 0.1mm thick. This appears to comply with the definition of sheathed but provides no additional physical protection.

There are manufacturers who make adequately sized connectors but they do tend to be at the more expensive end for the market but unfortunately high price is not a guarantee of a good connector block. Form often trumps functionality.

 

[Spectric]

It is obvious that the first drawing is the better way to connect the cable, with 0.5mm T&E cable now available some lights do not readily accept 0.75mm so can cause issues.

You have not stated the make or type of light being used but be aware that all downlighters used on a ground floor where there are floors above should be fire rated and best practice says all downlighters should be fire rated, the other option is to use fire hoods. The objective is to prevent / slow the spread of fire and allow people on the upper floors time to evacuate the building.

 

[ChaiLatte]

...with 0.5mm T&E cable now available

Could you suggest a supplier of 6242Y cable in 0.5mm^2 (or 0.75mm^2). The smallest I can see seems to be 1.0 mm^2. Thanks.

 

[Dabop]

How do you trim cable for LED lamps?

I was always taught to keep the outer insulation in the cable clamp or inside the junction box, so like the first picture, I'm being told this is wrong as the clamp does not fully close, it holds just as securely and looks better than the second photo to me but what would a professional say?

Ignore the monstrosity in the back ground that's what's being replaced.
View attachment 172888View attachment 172887

The first is correct, the second with the exposed inner cables insulation would be at least a level 3 'fix ASAP' in an EICR, many would say it should be a 2 instead (fix immediately)- whoever told you that it is the 'preferred' method isn't a licenced electrician and quite frankly shouldn't be touching electrics at all...
(the ONLY time that second one would be acceptable with only a single layer of insulation is when the junction point itself is inside a fully sealed external junction box ie back to 2 layers of insulation)

 

[ChaiLatte]

...I'm being told this is wrong as the clamp does not fully close

The upper clamp is made with multiple ratchet teeth (clearly visible on the right hand side). If there is one and only one correct position for the clamp, it would have a single tooth to suit that position. Why would the manufacturers go to the extra cost and complexity of making a multiple-toothed part?

Assuming it has only one correct position dictates that a single type (size) of cable is suitable. That would be a poor commercial strategy for any manufacturer selling into a world market, where local availability of cable varies (or local rules governing what cable is acceptable vary).

 

[naughtymoose]

Ozi, you are correct.

Section 5.17.2: No basic insulation of a conductor visible outside enclosure.

526.8
The PVC/PVC cable sheath is too short to reach the enclosure

This is a defect C2, potentially dangerous, urgent remedial action required.

Question- do these down lights carry appropriate test certification?

 

[MorrisWoodman12]

I'm not an electrician but I've taken several pieces of electronic equipment through type/safety testing. The idea running through all the standards is no one failure should create a dangerous situation. In this case if one level of insulation fails there is a second to keep the 'user' safe. Of the above case 1 adheres to this premise; case 2 does not and I would deem that unsafe.
Martin

 

[Skeety]

Definitely option 1 with the outer sheath of the T&E clamped. It may look like they are not fully clamping, normally the clamp is slightly tapered so will be tighter at the front.

Whoever told you it's wrong is wrong

Jon.

 

[Ozi]

Thanks all, I was fairly sure of my ground but wanted to make certain. These down lighters are IP65 rated below IP20 above, 220-240 V to the unit properly installed I assume they are more than adequate for a kitchen ceiling. They do not have an earth terminal like the ones posted by JonCooper27, not the same quality by the looks of things but CE marked by Kingfisher. Photo 1 is my completely illegal modification photo 2 the professional job I shall not be paying for till he comes back and puts it right. I like to try traids at home where I can check things more easily before letting them loose in rental properties, this guy will not be getting more work from me.

Thanks Spetric for the comment on fire hoods, I didn't know they were required when there is no loft insulation etc. but they will be fitted now you have told me.

Confession time - the monstrosity in the background is mine - a very temporary fix modifying a failed four tube florescent fitting to take 4 bulkhead fittings for the week till the sparky could get here - head hung in shame.

 

[TheUnicorn]

what a shoddy job from a proffessional