SOT - electrical box connection design

[Jeff Layman]

Reading the recent thread about connecting coaxial inside a wall plate, and how to make sure the coax outer was connected properly, led to thought about these wall box connections in general.

Basically, why are the components fitted to the removable front plate? Why aren't they fixed to the back of the box (whether that is fitted on or in the wall)? It seems to me that as the wiring - and that could be mains cable or coax - enters through the back of side of the box, it could be connected directly to a switch, socket, or whatever which would itself be screwed to the back of the box. The front cover would just have holes in it to accept the 3-pin socket, coax socket, switch, fuse, etc, and that would be fixed to the box in the usual manner.

There seem to me several advantages to this. Firstly, you wouldn't need three hands to hold the box front, cable, and screwdriver at the same time. Secondly, The cables wouldn't get moved, crushed, or distorted when the front is screwed on. Thirdly, you could test the connections without the front of the box being on to make sure it all worked before screwing the front on.

I'm sure I'm missing something here, but can't see it. Ceiling-mounted pull switches for bathrooms have this arrangement, and, although not exactly the same (and now not used much), junction boxes have always had the connectors fixed to the back of the box, not to the removable front.

[Brian Gaff]

I think often its one of space for the connections. Particularly important on RF of course as you need to preserve impedance matches, and with thick mains cables its often easier to do it with it all open and then bend the wires so they do not get crushed when assembled. Brian

[S Viemeister]

That's how it's done in North America - certainly makes decor changes easier...

[The Nomad]

And in some (?all?) parts of EU - .pt is a case in point

Avpx

[Robin]

ISTM you only avoid the need for three hands if you screw the switch etc to the back of the box /before/ you connect the cable(s). That seems to me to create challenges for (a) where cables are connected - eg it's not a good idea to have them where they can be touched if the front plate comes off or is loose and (b) cable management - especially if cable enters through the back of the box.

Separate "decor" covers is another matter - as eg with screwless fittings.

[Steve Walker]

It is worse if the cables are plastered in and can't be moved back and forth:

a) it is easier to make the connections outside and then bend the excess core length as you put the fitting in. You'd have less movement with shorter lengths of cable and it'd likely be harder to get the longer lengths out of the way while you work when the accessory is already in place.

b) different manufacturers have the terminals in different places and shorter lengths may not easily move to a different location upon replacement.

c) if the end of the cable becomes damaged you have spare on the longer lengths, although the faceplate is then closer to the wall while you are working and it beomes harder.

Another alternative is modular units, where you can feed the cables through the faceplate, mount it, connect the modules and then clip them into the faceplate - which is easier than manouevring two cables at once (for a double ethernet accessory for example).

What would make a great deal of sense is standardised back boxes across all manufacturers, with built in, high quality connectors that will last. Having connectors with terminal screws (braid clamps or IDC connectors depending upon service type) in standard positions, with fixed connectors. All the accessories to plug directly in and mains connectors to be recessed. Homeowners could then remove any accessory safely for decorating or replacement without touching the wiring (rather like central heating controller backplates).

By careful positioning, it should be possible for more than one connection to be incorporated at the same time - allowing say for satellite or TV and ethernet (as required by many set-top boxes).

The same IDC connectors would work for phone or ethernet.

All a bit too much I know.

SteveW

[John Rumm]

Having the ability to reposition / rotate the faceplate etc is sometimes very handy for getting it into a position you can actually see or reach to wire.

I suspect that main problem however would be the system you describe would lack the flexibility of the current arrangement - where you can use the same faceplate with a variety of back box designs to suit the application (e.g. surface, solid wall, dry lined wall etc).

Also modern building practice will tend to first fix the electricals, often before the plastering is done. Its bad enough when the plasterer half fills your metal back box with plaster that you have to clear out before adding the electrical bit. You would have more of a job trying to protect a backbox with built in electrical contacts and switch gear etc.

Some do, some don't...

In the past there was a fairly common range of MK made surface mount mains sockets that had everything built into back bit and worked as you describe. They were in reality often harder to wire since there was less leeway in the length of wires etc - they had to be exactly right to fit since there was little scope to fold excess wires back into the back box. Also you had to wire them before fixing the whole thing to the wall, which was more cumbersome that just holding the loose face plate since the whole thing was much larger.

[John Rumm]

Yup, I am a big fan of modular connections for signal grade stuff (network, phone, TV, sat etc), easy to wire, easy to repair, and very flexible without needing a big stock of obscure faceplates.

[Brian Gaff]

Yes but your switch could be padres mounted or on a wall box set into the wall, and at the moment the screw spacing is the same for both so the switch comes separately. If you look around new builds you see the boxes in the walls with no sockets fitted yet and just wires poking out, then along comes the guy with the switches, hoping nobody made the circuit live yet. grin. Brian