Strain relief for ceiling roses @ back boxes

[bsr]

Hello All

I thought that all junctions required strain relief so tend to use Ashley JBs or chocboxes. Is that right?

If so, how are back boxes and ceiling roses ok? I guess for back boxes it might be good practice to clip near entry but that's not always possible for plasterboard boxes.

I'm asking as I'm updating some lighting and when changing fittings trying to improve on the current methods of choc block wrapped in insulation tape and old ceiling roses shoved up into the void.

Thanks

 

[ericmark]

In places where the fixing means is intended to support a pendant luminaire. the fixing means shall be capable of carrying a mass of not less than 5 kg. If the mass of the luminaire is greater than 5 kg, the installer shall ensure that the fixing means is capable of supporting the mass of the pendant luminaire.

I have seen where the ceiling rose is fixed to plaster board, and I would think unlikely to support that weight. Also

Suspension devices for extra-low voltage luminaires, including supporting conductors, shall be capable of carrying
five times the mass of the luminaires (including their lamps) intended to be supported. but not less than 5 kg.

OK my ceiling rose I am sure can support that weight, but I am also sure many can't. As to fixed wiring the cable clips can hold the wire very well so there is no real need for cable clamps where the cable to the junction box is cleated in some way. I have had the argument when using SWA suspended from the ceiling to feed machines, my colleague wanted to use conduit, but the rules with conduit were little different to those with SWA so in both cases we should have run supports for the cable. I preferred SWA as common to move machines a few inches after initial installation to line up with something, my method allowed for that.

The old versions of wiring regulations said common sense should prevail that now seems to have gone, however there is a huge difference between a cable run across a loft space like an extension lead, to one clipped every foot or so.

 

[Taylortwocities]

Hello All

I thought that all junctions required strain relief so tend to use Ashley JBs or chocboxes. Is that right?

If so, how are back boxes and ceiling roses ok? I guess for back boxes it might be good practice to clip near entry but that's not always possible for plasterboard boxes.

I'm asking as I'm updating some lighting and when changing fittings trying to improve on the current methods of choc block wrapped in insulation tape and old ceiling roses shoved up into the void.

Thanks

In fixed wiring, cables need supporting. Therefore, as all cables must be securely clipped. The back box, junction box and ceiling rose are all screwed to something solid, or jolly well should be, so the cables cant /wont pull out!
Old ceiling roses shoved up into the void is forbidden.

Strain relief is needed if you have along length of flexible cable, with a box or something on the end that is not fixed. eg a downlight.

 

[ebee]

The old versions of wiring regulations said common sense should prevail

Common sense is quite uncommon these days Eric, well it never was Widley common but nowadays even less, look at car parking and driving even before looking at electrics etc.

Is it me just being old?

 

[mattylad]

Ordinary plastic ceiling pendants made these days just have a pretty weak plastic ring thing that goes on the cable and along with the 2 posts the wires are wrapped around supposedly prevents it being pulled through the lid to the pendant.

IMO a rather weak method that relies on a secure fitting of the lid.
I have the one that Eric posted a picture off in my main bedroom, a far superior product.
In the spare room I designed on myself, printed it on a 3D printer with added cable retention.

If your going to replace your pendants then I'd recommend getting good quality ones, if your wanting to hang a heavy shade on them this is even more important to do.

 

[Taylortwocities]

Ordinary plastic ceiling pendants made these days just have a pretty weak plastic ring thing that goes on the cable and along with the 2 posts the wires are wrapped around supposedly prevents it being pulled through the lid to the pendant.

That is for the flex that runs from the rose to the lamp holder. The comment relates to the fixed wiring side of pendants, JBs etc where there is no built in strain relief. There isn't any because, when installed properly, it is not necesary.

 

[bsr]

@Taylortwocities so is the rule that if the junction box or accessory is fixed, then strain relief not required? That makes sense.

 

[Taylortwocities]

@Taylortwocities so is the rule that if the junction box or accessory is fixed, then strain relief not required? That makes sense.

Junction box fixed, cables clipped. Standard wiring practice.

 

[sparkwright]

@Taylortwocities so is the rule that if the junction box or accessory is fixed, then strain relief not required? That makes sense.

It's only cables that are SEEN or TOUCHABLE that basically need strain relief.

For example, on a ceiling rose, typically the mains cables emerging from the ceiling aren't actually seen and can't be pulled or grabbed hold of, so no real need for strain relief. If these cables were visible and surface mounted, they would typically be fixed to the surface (eg with clips perhaps) and that would be the strain relief.

Where the pendant flex comes out of the bottom of the ceiling rose, this has strain relief - because it can be pulled and yanked about as it simply hangs there. Strain relief is provided by wrapping the cores around two little lugs. (I don't think typical ceiling roses have the best strain relief systems and amazed it's allowed today, but it works, but that's how they have been for decades and decades.)

Strain relief for most cables can typically be provided by
Cable clamps or cord grips.
Compression glands.
Lugs (ceiling rose pendant flex being the most obvious example).
Running the cable through a zig zag maze channel (no idea what it's really called, but found on some modern boilers, and some large outdoor garden junction boxes).
Cable clips.

 

[ericmark]

It's only cables that are SEEN or TOUCHABLE that basically need strain relief.

That does not sound right. I must admit a heated discussion as to if to gain assess to the space between the ceiling and floor above you need a tool, is the space an enclosure. I say no as some other trade may try to put their stuff through the same void, so a copper pipe could hit wiring without the person fitting the copper pipe having any idea there were any cables in the same void.

We all know we should clip the cable, and we also all know once both ceiling and floor are installed near impossible to clip the cable, without lifting all flooring or dropping ceiling, so it is not going to be done.

These

have three cable clamps, so can replace the ceiling rose, and hold all cables firm. As to maintenance free, with steel framed buildings there is often vibration which can cause screws to come loose, and so we need maintenance free, but in most homes even if we could gain access for maintenance it is rare for any wiring to be serviced, hard enough to get some one to do an EICR never mind a service. I have done them with batching plants where it is a steel frame, but never in the home.

Even the old junction box, there was normally some pressure from the lid onto the cables. These also have grips which should help to hold the cable in the box, however if one has to select this with terminal screws but a good cable clamp or this with no terminal screws but also a little hit and miss depending on cable size on gripping cables, although the latter is when we should use, I would select the former.