Wiring a container

[Lewiselectric]

Apologies if this has already been asked guys - I’m sure it must have been - I don’t do a great deal of electrical work these days but have agreed to do this job for someone I know. I’ve fed containers before, but this was in a dockyard. We fed 3 phase sockets to the outside of a building and plugged the containers in as they had refrigeration units and weren’t staying put for long. This job however is a bit different as the container will be used as a workshop next to a building and is permanent (at least for the foreseeable future). As far as I know regulations for this will be different in terms of earthing: am I right in thinking I will have to use a rod and put the container on a TT? I don’t yet know the earthing arrangements of the building which the supply for the container will be coming from. Another issue is that the container is about a metre away from the workshop building which has metal cladding on the outside fixed to structural metalwork. Will this pose a problem as you could touch both at the same time?

apologies if this is very basic stuff for some of you, I just want to get this right.

 

[cliffed]

Looks like the container is metal so will require main earth protective bonding conductors ideally TT system & 10mm MEPBC.
Real problem if you can touch 2 different earthing systems @ the same time especially if TNCS.

 

[timhoward]

What is the supply earthing and workshop earthing?
Is the floor of the container going to be the bare metal?

Even though open PEN faults are seriously rare, and I’m normally a proponent of keeping TNCS for outbuildings, I do tend to agree that metal containers where you are walking on and contained by the (worst case) diverted neutral current push me to think TT is better in this specific case. Not everyone agrees on this!

The metal cladding on the workshop should already be bonded if is touching structural steel. This could be tested with a wander lead.

Standing on real earth, and touching the cladding would appear to be the same deal whether the other hand is touching a TTd container sitting on real earth or not.
If the container was TNCS you have a chance of tingle off both but they are at the same potential.

(Btw the required main bond size is smaller if TT.)

 

[Lewiselectric]

Thanks guys for your reply, very helpful. I’m unsure at the moment if the container will be bare flooring or not. But of a difficult one, this one. I think I’ll need to make it a TT but things like the fact it’s within touching distance of the main building cladding was a concern

 

[cliffed]

Thanks guys for your reply, very helpful. I’m unsure at the moment if the container will be bare flooring or not. But of a difficult one, this one. I think I’ll need to make it a TT but things like the fact it’s within touching distance of the main building cladding was a concern

Understand your concern & many wouldn’t even think about it….recommendation on the EV charging points when TT … & an outside tap can be touched on a TNCS, place a plastic insert into the pipework…
In your situation I’ve read put an earth electrode near by connected to the existing earth system.Obviously away from the TT system ….do not interconnect the 2 systems though.