Wiring method-Metal garden sheds?

tomdempsey200

anyone familiar with wiring these?

going to look at one...what's the usual wiring method?

nym and round pvc conduit?

thanks

2011

tomdempsey200 wrote: »

anyone familiar with wiring these?

going to look at one...what's the usual wiring method?

nym and round pvc conduit?

thanks

Either could meet the ETCI requirments, however I think you may find it easier in NYMJ. As it may not be possible to clip the NYMJ it may be easier run it in PVC conduit and use "open bends". If I was doing it this was I would use stuffing glands also.

Just be aware that NYMJ is not UV resistant, so dont use it uncovered outside.

2011

On another note, in my opinion the frame of the shed should be earthed. It is not likley that equipotential bonding would be required, but this could be verified by using a multimeter.

tomdempsey200

ya if it's extraneous i think a main bond is required alright

i doubt many do it if they're using a small sub-main

Stoner

I did one fore a neighbor recently it was right beside his house.

I added an earthrod even though technically is might not be the best thing to do but I thought a 10 Sq earth to a copper rod was the way to go as the whole shed is metal.

I used NYMJ and cable tied it tight against the under side of the metal frame to get as much mechanical protection as possible. I also did not use compression glands for the sockets, I just used the breakouts at the back of the plastic boxes and used self tapping screws. They held the boxes solidly to the steel and also pinned the cable in tightly to the grooves in the panels.

I cabled into a steel back box for a metal isolator as my first device, this was also self tapped to the steel frame.

The only issue i has was that the self tapping screws come out the far side of the shed, as mentioned his was against the house so I had all his services on the wall parallel to the house so the screws were not sticking out on the exposed side of the shed.

tomdempsey200

ya

i'm gonna use some light 50mm tray screwed onto the frame for the nym

simple enough job really

needs an isolating switch alright and main bond(if extraneous)...

what's the story with rods on these metal outbuildings? not sure on that one

Stoner

Well there are a few posts here already on not having a second rod, I just wanted to do it as it's an old installation and I couldn't see the existing rod, or any rod for that matter

2011

The shed would not require an earth electrode assuming the following:

1) The installation already has a suitable earth rod, properly connected.

2) We are talking about a typically sized garden shed not something the size of an aircraft hanger

tomdempsey200

reci used to tell me not to put down a second rod

never really looked into it

2011

tomdempsey200 wrote: »

reci used to tell me not to put down a second rod

Under what circumstances ?
Sometimes multiple earth rods have to be installed such as milking parlours or if the resistivity of the soil was particulary poor.

tomdempsey200

ya domestic i was on about....2nd rod for outbuilding
is there any harm in it?
could be BS from the reci inspector dont ya know!......



there's nothing in et101 on resistivity for TN domestic installations anyhow afaik

Bruthal

In domestic situations in estates with tn-cs, multiple earth rods connected at different points in the single phase installation could possibly cause problems for that installation in the event of main neutral loss at mini pillar, with other houses connected to the same affected neutral bar having a route through the multiple earth` s inside the house installation that has the extra earth rods beyond their DB.

Of course, any earth rods in the affected houses will combine to form some sort of neutral conductor (almost always a poor one) when the main minipillar neutral fails, but in theory, there is an extra route through the installation that has outbuildings etc with extra earth rods.

So having earth rods connected to different points beyond the DB earth bar in a neutralised installation is probably not highly recommended.

Overall though, it probably would`nt cause that much hassle.

2011

tomdempsey200 wrote: »

ya domestic i was on about....2nd rod for outbuilding
is there any harm in it?

There are small single phase electrical installations that have multiple earth rods such as a milking parlour (page 332 and 333 of ET101 regulations shows this).

could be BS from the reci inspector dont ya know!......

From a RECI inspector, I would find that very hard to believe :rolleyes:

there's nothing in et101 on resistivity for TN domestic installations anyhow afaik

There is. Page 119 of ET101 section 542.2.2 applies to all installations (or it would be stated otherwise):

Consideration shall be given to local soil conditions. One or more electrodes shall be selected, depending on soil conditions and the maximum permissible value of impedance to earth.

Note: 542.2.3 (b) states that installations that have a supply that does not exceed 250A a single earth rod is "deemed sufficient", however it also states that the above proviso still applies.
In other words, a single earth rod may be sufficient but more may be required depending on factors such as soil conditions (resistivity).

Bruthal

Connecting multi earth rods to the dB earth bar is not quite the same as connecting multi earth rods throughout the house installation though.