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Dodgy junction box comments


 
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Ianm

from United Kingdom

Joined: 04 Jan 2003
Posts: 56
Location: United Kingdom

PostPosted: Mon Mar 17, 2003 6:47 pm Reply with quote

Following on from recent posts I would like comments about the best thing to do with a junction box. I have been putting in a new light and found that all lights and switches for one particular lighting curcuit were run out of a humungous junction box with a 12 way 5 Amp terminal block. Each block has 3/4/5 wires attached (in both directions) so all lights and switches run out from it. The earth wires are coiled together as there is no room in the blocks. Obviously the junction box won't close cause it's packed so tight and there a red and black sleeves exposed. Also the wire in the box is quite brittle with age.

I could - leave as is
or - replace with another (newer) humungous junction box
or - convert into multiple junction boxes for each light and switch

Most of the lights are wall lights and are plastered in so I cant easily loop through them.

I have seen some posts here which state that junction boxes should no longer be used and that loop-in is the standard.

Any comments?

Ian
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MANDATE

from United Kingdom

Joined: 06 Mar 2003
Posts: 2286
Location: Manchester,
United Kingdom
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PostPosted: Mon Mar 17, 2003 9:36 pm Reply with quote

I know of no reason why junction boxes should not be used.
Basically there is no difference, the modern ceiling rose is a junction box and both have live/neut/switch/earth plus the wires to the lamp.
Access to the ceiling rose is from the room below it and there's not that much space to work with.
Junction boxes are under floorboards or in the attic but its easier to identify the cables and there's more room.
It's whichever suits you best, I like the junction box because the terminals are large and i cant lose the screws on the floor.
Remember for each light you need boxes with 4 terminals but if you intend to take spur a off between lights then a box with 3 terminals is ok
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alexnic

from United Kingdom

Joined: 19 Dec 2002
Posts: 186
Location: United Kingdom
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PostPosted: Tue Mar 18, 2003 9:08 am Reply with quote

I would replace the junction box with a larger one ... 6"x6" or 8"x8" depending on the amount of cables.
Sometimes it's best to use a central JB when rewiring (rather than the loop-in method) especially if existing conduit drops to the switches are used ..as found in older houses.

If you do decide to change it remember and identify the cables and their joints prior to starting .... the brittle cables sound a bit 'dodgy', should get it checked out as this could be a sign of burning due to bad connections especially if it is PVC cable
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amtodd

from United Kingdom

Joined: 06 Jun 2002
Posts: 110
Location: United Kingdom
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PostPosted: Tue Mar 18, 2003 5:32 pm Reply with quote

Junction boxes have a U shaped threaded terminal. This shape does not limit the number/ size of wires which can be placed under the machine screw. Too many wires or the wires being bent mean the screw cannot bite onto the terminal properly without pushing hard. If you push hard, the u-shape splits open a little bit, and the screw fit is even worse. This kind of loose connection causes fires.

In a rose / switch/ socket etc., the terminal is a solid block of brass with a hole drilled one way, and a machine thread drilled part way through in another direction. The terminal is a lot stronger, and the size / quantity of wires connected is limited by the size of the hole. It is therefor easier to ensure a good connection.
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Ianm

from United Kingdom

Joined: 04 Jan 2003
Posts: 56
Location: United Kingdom

PostPosted: Tue Mar 18, 2003 7:35 pm Reply with quote

Thanks for the comments.

Looks like I should definately replace, I'll follow up on the ideas icon_biggrin.gif
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amtodd

from United Kingdom

Joined: 06 Jun 2002
Posts: 110
Location: United Kingdom
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PostPosted: Wed Mar 19, 2003 8:23 am Reply with quote

Ooops, icon_redface.gif sorry, I may have given the impression I don't think J-boxes are safe. My previous comments were only the reasoning for them being removed from the regs. (Which implies the IEE think they are unsafe.)

IMHO in the hands of a skilled tradesmen J boxes are as good as the next item in the circuit, and certainly better than terminal blocks, which is what most people replace roses with when they remove the original rose and replace it with a fancy fitting.
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