Thoughts on tidying up a garden wiring box

[Milleniumaire]

Around 9 years ago as part of a garden makeover, an electrician installed a number of SWA cables and light fittings and connected them up in a large plastic "junction" box in the garden. Here's a "clean" photo showing the full interior of the box, however, as this is a little old, it doesn't include the additional socket cable so I've added the 2nd photo to show this cable (at the far right):

20210509_161559

• Milleniumaire
• 17 May 2021

Garden wiring box

Garden Wiring Box New.jpg

• Milleniumaire
• Tuesday at 8:38 PM

Please note: some of the wires are currently disconnected for testing so the photos are really to show the spaghetti state of the wiring.

What may not be clear from the photo is that the banjo earth rings for each SWA (except the far right SWA) are all installed underneath the box i.e. outside it, and earthed to the inside using brass screws, fitted through holes drilled through the box.

I would like to tidy up this wiring and would appreciate your thoughts on how best to do this.

As you can see, currently, a couple of terminal blocks are used; one for the lights and the other for the water feature pump.

There are two SWA cables feeding power into the box (left most SWA cables), with each connected to a double pole switch in the house. One of these SWA cables is (normally) connected to 5 other cables in the box (4 SWA and 1 cable). The other SWA cable is connected to the water feature pump SWA. So, in terms of connections required:

Lights (switch 1):
Live 1 in and 5 out = 6 live wires on switch 1
Neutral 1 in and 5 out = 6 neutral wires on switch 1
Earth 2 in (earth and SWA metal) and 9 out (5 earth + 4 SWA metal) = 11 earth wires on switch 1

Water Feature Pump (switch 2):
Live 1 in and 1 out = 2 live wires on switch 2
Neutral 1 in and 1 out = 2 neutral wires on switch 2
Earth 2 in (earth and SWA metal) and 2 out (earth and SWA metal) = 4 earth wires on switch 2

I notice the existing wiring connects all the earth cables together, regardless of switch. Are there any advantages to separately the earths by switch?

My thoughts:
I could use wago connectors for the water feature pump but this doesn't really tidy up the cable, just replaces the terminal block with wagos. Using wagos for the lights is a little more difficult due to the 11 earth wires. Also, the standard wago connectors don't have any method of fixing them to the plastic box.
I was wondering if a DIN rail could be used to tidy up the wiring and appropriate connectors purchased. I see that wago make a TOPJOB S series product, but there are so many types of connectors etc. I'm not exactly sure how these work other than the required connectors are added to the rail and jumper bars used to combine these connectors into groups of connected wires e.g. switch 1 live, switch 1 neutral etc.
I could als replace the banjo earth rings with piranha earth nuts to bring all the earth connections inside the box. The screw holes would then need to be filled (electrical putty?). This doesn't really help tidy up the wiring, but in my opinion is a better way to connect the SWA protection to earth.

I would appreciate your thoughts/ideas.

 

[mikehammer69]

There's nothing much worth tidying up

Do a few tests earth continuity and IR - fix your problem

 

[ericmark]

Any box where the wires are fixed

makes testing easier, sometimes called a wiring centre

but there is no real need.

I could als replace the banjo earth rings with piranha earth nuts to bring all the earth connections inside the box. The screw holes would then need to be filled (electrical putty?). This doesn't really help tidy up the wiring, but in my opinion is a better way to connect the SWA protection to earth.

That is rather a complex question. What we are really looking at should a garden be TN or TT earthed. This may help but it is down to what is in the garden, and not something I could advise on without being on site.

 

[Milleniumaire]

Any box where the wires are fixed View attachment 420725 makes testing easier, sometimes called a wiring centre View attachment 420726but there is no real need.

That is rather a complex question. What we are really looking at should a garden be TN or TT earthed. This may help but it is down to what is in the garden, and not something I could advise on without being on site.

Sorry ericmark, but I think I must be missing the point of your post as I don't really understand the relevance of the document you have provided. This is not a new installation, or an installation in an outbuilding or garage. I'm simply suggesting that the method of earthing the SWA protection be modified to use something which I believe is mechanically better and neater. I understand that regulations can change over time, but I wouldn't have thought it would be necessary to change the existing wiring box from TN to TT, simply because a different method of connecting the SWA protection to earth was used?

 

[ericmark]

To export TN-C-S out of the bonded area can cause a problem with a loss of PEN. And it is near impossible to know if the supply is TN-S as at the head they and look the same, so we assume it is TN-C-S even if really TN-S.

So in the main outdoor equipment is class II, so earth not used anyway, so running a TN-C-S earth to sockets, is not really a problem, as the earth is rarely used. But we want the earth terminals and any cable glands to be shrouded or ware unlikely to be touched. Using the odd class I item outdoors, for a short time, one would be extremely unlucky to have a loss of PEN at the same time.

However, items used for a long time, like charging an EV, powering a caravan, or a metal shed, then we need to take extra precautions, EV is the odd one out, where loss of PEN detection is used, but with caravans for example TN-C-S supplies are banned.

But as my father-in-law pointed out, his meter cupboard was within arms length of the caravan and the meter cupboard was earthed to the TN-C-S supply, so safer if caravan has the same earth system. And since parked on a drive of slabs, very unlikely even if the skin of the caravan was live, than anyone would get a lethal shock.

So with a wooden shed, no problem, but if I was to take power to my tin garage, I would likely use a TT earth system, but I can park 4 cars between garage and house, no meter cupboard to consider in my case.

And this is the problem, we need to consider what else is around, no good using an earth rod which is really close to a water or gas pipe, as it may not be a true earth. So in real terms we have to assess the risk, it's not as cut and dried as some try to make out.

So since I have solar and a battery with an EPS supply to freezers and central heating, I need an earth rod for the TN-S supply when the grid supply fails, as the grid earth is not disconnected when the grid fails, the earth rods do not want to be too good, as don't want massive PEN fault currents through my earth rod, seen it once, where a radio hams earth wire to his shack melted when the PEN was lost, as his radio earth mat was rather good.

But since I do have an earth rod, even with loss of PEN, the DNO earth is not likely to rise to a full 230 volts, but as to what voltage, will depend on loads and other earth rods, and solar and EV's make it worse.

Years ago if we lost the PEN since all homes have around the same power use the voltage would not rise that much. But solar and EV's have an automatic disconnection if the voltage is out of range. So as a phase load is lost, its voltage will raise.

And also how much is used, since 9:30 am today my use has been zero, so no longer are the phases balanced, so as a result more current goes down the PEN, so loss of PEN cases are raising.

PME the M stands for multiple, and the idea was there were so many earth rods, it would not even with loss of PEN raise too much, but PME is TN-C-S, but that does not mean TN-C-S is PME, it may not have loads of earth rods.

This is why I linked to the IET article on outbuilding supplies, it gets rather complex, and there is no one method suits all.