On 30/08/2012 10:30, Adam Funk wrote:
On 2012-08-29, Roger Mills wrote:

On 29/08/2012 13:09, Adam Funk wrote:
Roger Mills wrote:

http://www.tlc-direct.co.uk/Products... UbMtAodsTcAEA
...
I noticed that while browsing the catalogue recently& this seems like
a good place to mention what I was wondering about.

I guess it's called "Maintenance Free" because it can be buried under
the floor without worrying about future access to check that the screw
terminals are still tight. Is that correct? What kind of terminals
does this box use that are more secure than normal screw terminals?

Basically, they're spring-loaded clamps. Some have levers which open the
clamp, and make it easy to insert and remove wires. These are ok for
solid or stranded wire. Others are just two metal strips in the form of
a V, sprung together at the pointy end. Pushing a wire down the middle
separates the strips - which then grip the wire. This type is only
suitable for solid wire, and is more difficult to take apart - but you
can usually remove a wire by twisting and pulling at the same time.

I wondered if they were sprung like that. I guess they are secure
because the cables are clamped in the box itself so the individual
wires can't be pulled loose (unlike a traditional junction box).

Not really. Strain relief is something different. With this sort of
connection, the security of the actual electrical connection is better
than a junction box with screws because of the constant spring pressure.
The screws in a junction box can work loose over time - possibly due to
expansion and contraction - and you might then get arcing and, in
extremis, a fire. That's why anything with screw connections needs to be
'accessible' - whereas these maintenance-free jobbies don't.
--
Cheers,
Roger
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