BS 7671 Rules on Joining Cables.

[david01280]

I understand that the rules say that cable joins using junction boxes with screw fittings have to be accessible for inspection.

This seems fair enough, but I have a damaged cable in a lighting radial circuit which is under the floorboards. How do I repair it without using a junction box? I don't want to have to take loads more boards up to replace from rose to rose.

 

[Steve]

you would need to use a ratchet crimper and crimps. See if you can borrow the kit needed. Then wrap the whole joint in heatshrink.

Of course, a lot of houses have inaccessible junction boxes, ours is certainly no exception . . . but of course i'm not recommending you break any rules here.

 

[Lectrician]

Use a JB and be done with it. I would prefer that than a crappy heat-shrunk joint.

 

[Dippy]

Where does it say that having to lift the floorboards means that it is not accessible for inspection?

 

[Steve]

Where does it say that having to lift the floorboards means that it is not accessible for inspection?

its debatable - what if the house subsequently has laminate floor or tiles put down? it wont be accesible then, without ruining the floor! however, if its just carpet, then i suppose it is accessible, but theres no telling what floor covering will be installed ina few years!

 

[Lectrician]

The NIC's view, for whats it's worth, is under ANY floor is in-accessible. Even carpet.

 

[fattony]

Use a JB and be done with it. I would prefer that than a rubbishy heat-shrunk joint.

Isn't a crimp joint not technically a joint but a continuation of cable?

 

[Softus]

Use a JB and be done with it. I would prefer that than a rubbishy heat-shrunk joint.

I'm curious, having noticed that most electricians believe a crimped connection to more reliable and longer lasting than a joint made in a screw terminal.

Lectrician - is your experience the opposite to that of most other electricians on the forum?

 

[sparky40]

Unless we are going to start charging for detailed drawings, and start fitting accessible carpeted floor outlets this reg is over the top when dealing with extensions and the like, i believe. Crimping has it's advantages but a correctly terminated joint box that over decades may 'vibrate' etc loose to me is , and has never been a safer option seeing as our crimping tools are not always calibrated. Any loose or dodgy connections should show themselves during testing. Maybe a bs j.b should be made to keep us, and the people whom know nothing about electricity all happy.

 

[RF Lighting]

Maybe a bs j.b should be made

That would be far too sensible.

 

[sparky40]

Sorry, forgot, they do make a bs j' b,.I suggest dropping into sight by means of cheap mini trunking just below ceiling level etc, and fitting a small but classy ornamental 'boxing' around it. Accessible and a nice 'feature'.

 

[Pensdown]

As Lectricain has said, having JB's that are not easily accessible is an NIC recommendation, it's nothing to do with 7671. I also agree that I prefer seeing either a correctly terminated JB or if you prefer, crimps used within the JB instead of the screw terminals. Heat shrink and crimps have there uses but IMO not for a normal joint.

I'm curious, having noticed that most electricians believe a crimped connection to more reliable and longer lasting than a joint made in a screw terminal.

IMO the difference between a well terminated junction box and a crimp is insignificant in 99.9% of cases.

To get into pluming terms, whats the difference between a well done compression/pushfit joint and a well done solder joint? I would assume in 99.9% of cases very little?

 

[david01280]

Thanks for the replies.

I see there is a BS standard crimp. I assume there are different sizes for each cable size. What gives it it's mechanical strength? Would you use crimps on larger cables, for example extending a cooker supply? Does the heat shrink give the same level on insulation as the original two layers in the twin and earth?

Lots of questions I know, thanks for your help

 

[Softus]

To get into pluming terms, whats the difference between a well done compression/pushfit joint and a well done solder joint? I would assume in 99.9% of cases very little?

I don't understand your analogy. Do you mean in terms of:

1. Mechanical strength;
2. Appearance;
3. Likelihood of leaking;
4. Electrical conductivity;
5. Demountability.

 

[Pensdown]

I meant being fit for purpose. A soldered joint maybe better than a compression joint just like a crimp connection mabe better that a screwed connection. But both are still fit for purpose.