I'm currently working on constructing a mobile power distribution unit and I need some assistance with a specific aspect of it.

The unit is designed to accommodate both types of power networks found in Norway: TN and IT. We've integrated a 6-pole cam switch to select the desired network. In Norway, different locations have different power network standards. The IT 230V network is common in older venues, while the 400V TN network is prevalent in newer locations. This means we always need to carry different power distributors. My goal with this device is to handle both scenarios, utilizing a CAM switch similar to a Network/Generator switch.

I've put together a drawing to illustrate the concept and wiring involved. I apologize for its amateurish appearance, but I believe it effectively communicates the intended concept and wiring layout.

I'm currently debating whether the chassis wiring and mains cable of the power distribution unit need to match the 5G16mm2 wire used in permanent installations for 63A 400V three-phase outlets. I've come across information suggesting that certain non-PVC cables, such as PEX or EPR insulated cables, and LSZH cables, have higher current carrying capacities, often exceeding 63A for 10mm2 three-phase cable. For instance, PEX or EPR insulated copper conductors, with a conductor temperature of 90 ºC and a reference ambient temperature of 30 ºC, can carry 75A when installed "free in air". Given the mobile nature of my device and maximum mains cable length of two meters, I assume my mains cable would be considered as installed "free in the air".

Additionally, in the drawing, each phase is connected to four RCBOs, each hooked up with 2.5mm2 wire, totaling 10mm2. While it seems reasonable to utilize 10mm2, I'm concerned there may be aspects I'm overlooking.

I've come across mentions of "chassis wiring" which supposedly allows the use of smaller wire diameters, but I'm uncertain about its validity.

Using 7G10mm2 LSZH (JZ-500 from HELUKABEL) cable would streamline connections inside the device. In this case, I would only need to correctly connect the wires to the mains plug, and all six wires could be directly connected to the 6-pole CAM switch inside the box. With 5G16mm², I need to do some splitting inside the box.

However, since Norwegian NEK400 does not mention cables with LSZH insulation, I lack a reference point for making a decision on which cable to choose.

For an IT 230V 63A three-phase power network, using 7G10 mains will actually result in 20mm² per phase, so there's nothing to worry about.

The only question then would be about the 400V 63A three-phase TN power network mains aspect. We have a 63A 400V TN network connected with a 7G10mm² [three-phase mains] LSZH cable of two meters, free in the air. Will 10mm² per phase be enough, or do I need 5G16mm²?

[I have a background in electronics (middle school in Poland) and electrical systems (completed in Norway).]

On the two pictures below, you can see the 32A version that was previously built, and on a third picture, a partial view of the 63A power distribution unit that I am currently constructing.

schematic 32A version enter image description here enter image description here


1 Answer 1


You may use the following chart to have a look at the required wire gauges. I've always used a chassis wiring gauge for connecting my device to the mains socket. Please note: this is my personal experience only. Take necessary precautions when you are performing tests. You may use a thermal camera to check the temperature of wires when in action and match it with the manufacturer's ratings.


Note: As of my understanding, Transmission wiring is for long-distance power transmission. From Generators and power substations.

Again, these are my personal opinions only.


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