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Help me put together junction some boxes


New Member

I’m putting together some junction boxes for domestic lighting using RS own brand DIN terminals in a suitable enclosure (home automation later would favour grouping the wiring into a limited number of JBs with space to accept relays later).

One thing that came to mind was to do with these:

They are the special DIN terminals that have a screw operated clamp to the DIN rail which claims to provide electrical continuity.

How might I decide if these would provide suitable and reliable continuity for the circuit CPC on say a circuit protected by a C10 RCBO? Or do you reckon they are just fine?

Points I’ve considered:

Reliability – these clamp to a plated steel rail – so providing the plating holds and the rail does not corrode, then OK
Clamping action seems positive.

Contact resistance: haven’t attempted to measure yet, but I suspect it would be off the bottom of the range of my Megger.

Fault current – worst case scenario: hundreds of amps but no more than 1kA for a very short time.

There is a little leeway in that the circuit is RCD protected, but I feel it would be bad practice to factor that in as a key design consideration.

What do you folk think of such devices?

Many thanks,


Well-Known Member
Most Helpful Member
The link does not work, it just goes to the famaga site.
Can you link direct to an RS page, or give a part number?

The only terminals I know which electrically connect to the steel rail are earth terminals. If that's what you mean, as long as you use the appropriate size & current rating they should be fine.

I would suggest you always use the "heavy duty" / 15mm deep DIN rail, it's much stronger than the basic type. The thin stuff can crush under the pressure of some screw clamps and things come loose.
eg. This style:

As you mention home automation..
Have you seen the size of such as Fibaro modules? They are tiny; this type of thing:

I have one here; 42 x 35 x 16mm for such as a light dimmer, one 3KW switch or a dual channel switch rated 10A total..

And you can now get wall switches with Z-Wave built in from around £20, so no extra modules needed at all.

Z-Wave is superb, as everything is two-way - use a web interface or app and control devices or lights.
Plus, when you operate them locally the status changes on the web interface or app, unlike most other systems.
And it all makes work together, there are no tie-ins.

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