Din Rail Terminal Blocks

[Tunni]

Hi all, I'm looking to shift the wiring of an exceptionally awkwardly placed old fuse board to a shiny new 18th ed compliant board a few metres away. As all the wiring will still have to come to the new board from the old location, literally at the back of a 2m deep cupboard and directly under the bottom but 1 stair I'm thinking I'm going to need a fireproof enclosure and some lovely sure connections.
With that in mind I was thinking of using din rail mounted terminal blocks, my only concern with this is that the earth terminals all secure with electrical contact to the din rail. To my mind that will make any R1+R2 reading a nonsense as there will be parallel paths to all circuits regardless of the connection at the consumer unit.
With this is mind should I just bin the idea of using the earth terminals and opt instead for a generic beige terminal? I've not had much to do with this panel wiring kit so anyone out there who does or has an informed suggestion I'm all ears.
Yes I know I'll need a switch fuse for the tails etc...

 

[ToadHall2]

With that in mind I was thinking of using din rail mounted terminal blocks, my only concern with this is that the earth terminals all secure with electrical contact to the din rail.

Not necessarily. I generally use the Weidmuller WDU 2.5 series (800V, 25A), available in a rainbow of colours. You could just use green feed through ones. I agree they also supply the WPE 2.5 green/yellow that clamps electrically to the DIN rail, but you are not forced to use them (although you might want to use at least one to earth the DIN rail). They also do WDU 4, 6 .... 35, but larger sizes are not available in such a wide range of colours.

 

[Tunni]

Blimey talk about brain fart! It won't make the blindest difference either way will it?! I am concerned about being able to individually isolate a cpc for continuity testing, particularly on an installation I don't know other than by inspection and button pressing though. This is the question really. Is a separate lurking 2nd earth bar (i.e hidden away beyond the consumer unit) a problem for you informed folks or something that doesn't concern?

 

[James]

Your R1 and R2 values will be true.

I would only bring a single earth cable from the MET to the din rail earth terminal, no point in taking a seperate cpc for each circuit back to the board if they are all going to be joined together at your junction box.
ensure the earth cable from junction box to the MET is at least the size of the main earth cable.

If you are using twin and earth for all the cables between new board and junction box, the cpc should be connected and you can do away with the main earth cable previousley mentioned.
do not worry that there are parallel paths because the values will be better than without.

it is a similar issue to when metalclad sockets and switches are screwed to a metal framed building. results are always far better than expected.

p.s. this junction box will be accessible for future maintenance i presume?
A note stuck on the inside of the new DB would help any future spark that is working after you.

 

[telectrix]

or use plain connectors, not the earthed ones.also you don't need a metal box as it's not a CU or similar switchgear.

here's one i made earlier (2015).

 

[partplonker]

or use plain connectors, not the earthed ones.also you don't need a metal box as it's not a CU or similar switchgear.

here's one i made earlier (2015).

That looks great. I'm planning to do something like this to tidy up an ancient 240v fire alarm system that is currently unenclosed spaghetti in screw terminal blocks that someone threw in a cupboard in the 1970s.

 

[pc1966]

As above.

I tend to use some colour if possible as it makes it easier to keep the order of terminals as you go and reduces the chance of any screw-up. I have tended to use the Entrelec ones as have had no complaints, but others have their own preference.

RS is not the cheapest supplier, but easy to locater them. For example a search for ZS6 gives you these colours/options:

https://uk.rs-online.com/web/c/conn...114&pn=1&sort-by=P_breakPrice1&sort-order=asc

If you have some circuits needing 10mm then bigger versions are available (e.g. ZS10 or ZS16, etc) but not always so many colours!

 

[Tunni]

Nice one folks, thanks for the replies. This junction box might as well be at the gates of Mordor for all the accessibility it has so I think the single cpc route will be best skipped here. I will too be running straight T&E back from the box so for the sake of a few quid it might as well take the cpcs too. I'll take the tip of earthing the bar, there's a couple of 6mm going through I reckon I'll keep the rings and radials, lights etc separate and add the extra connection there. I reckon the other cpcs I'll keep separate with some yellow or similar terminal. I'll add a note on the schedule at the board too, nice tip.

 

[R-fur]

Edmondson's are dealers for Phoenix terminals so they might be able to help you.
You also get spring loaded terminals which are more reliable, dont know if they are classed as MF. In industrial locations hooked blade crimps are used as they give a more positive location.

 

[Lucien Nunes]

Wago and others make screwless DIN-rail terminals; they won't make the junction box MF to BS5733 but they do make it unnecessary ever to check tightness etc, you could just look inside the box for an EICR. In a domestic setting I would certainly keep the CPCs of an RFC separate at the junction, if not all of them. If providing a common connection, because the total earth leakage might be expected to exceed 10mA, the common CPC should satisfy the requirements for a high-integrity connection.

In our (non-domestic) applications we often need large through-boxes for many dozens of circuits. We normally earth to the rail and provide a common connection equivalent to the largest circuit present, not less than 4mm² in conduit but more usually 6mm² or more lugged and bolted, and typically make a separate connection to the metallic containment.