We have a building with a 200 amp 3 phase supply. We have a 20 foot shipping container approximately 40 meters away from the main fuse board. We would like to run a dedicated cable from the fuse board to the shipping container. The cable will have to be buried under a gravel car park for approximately 20 meters. Maximum load would be an 18,000 BTU aircon, a few LED lights, and some other small electric appliances. The aircon will be used a lot as the container is in the sun.

 

1. What type and size of cable would you recommend please? Can it be purchased in 50 meter lengths?

 

2. There would be minimal chance of anyone ever digging a hole anywhere along the route, so does this type of buried cable need to be in a protective pipe for the distance it runs under the car park?

 

3. At the container end, would you suggest wiring the incoming cable directly to the new sub fuse board inside the container? Or would it be better to wire the incoming cable directly into a commando type socket, and then run a commando lead from the socket to the incoming supply of the sub fuse board in the container? A consideration is that the container may be shipped off-site at some point in the future, so "unplugging" it would be beneficial at that point.

 

4. What is the best way to earth the container? a. Use the earth from the main fuse board; b. do not use the earth from the main fuse board and instead use an earth rod buried next to the container; c. Use the earth from the main fuse board and use an earth rod buried next to the container?

 

Thank you for all your help. I want to get some input before I talk to the local electrician who will suggest his own way of doing it if I don't have any better ideas.

18k BTU A/C plus a few lights, say 2kW max, 2.5mm2 would be OK, I'd actually pull 4mm2 and protect with a 32A RCBO breaker at the supply end.

 

1. If going underground you need NYY cable https://www.bangkokcable.com/system/product/file_upload/211102_450!750V 70C NYY_1-4core_Rev04.pdf Should be available in 50m lengths, check Lazada for by-the-metre suppliers.

2. Although NYY can be buried direct I recommend the black polypropylene conduit for extra protection.

3. Wiring to a trailing 32A Commando socket (remember it's a live end) is a smart idea.

4. I would NOT use the main building ground, run 2-core cable and bash in a local rod at the container for a TT island.

 

Bond your container, the rod and the container electrical ground together, we don't want any voltages vs the ground you're standing on (site workers have died getting hold of a container door handle!).